Engineering exposed active facets by doping impurities can dramatically modify the morphology and physicochemical properties of nanocrystalline hematite. In the work described in this paper, through the combination of laser ablation in liquid and hydrothermal treatment techniques, faceted Mn-doped α-Fe2O3 nanocrystals (NCs) were prepared by adjusting the doping level of elemental Mn. With the increase of Mn doping level, the hematite crystal evolved sequentially from isotropic polyhedral nanoparticles (NPs) to {116}-faceted saucer-shaped nanosheets (NSs), and then to {001}-faceted hexagonal NSs. Electrochemical stripping tests revealed that the Mn-doped α-Fe2O3 NCs show a facet-dependent adsorption ability toward Pb(II), Cd(II), and Hg(II) heavy-metal ions; that is, {001}-faceted hexagonal NSs exhibit high and selective adsorption toward Pb2+ ions, while {116}-faceted saucer-shaped NSs present strong and selective adsorption toward Cd2+ and Hg2+ ions. Density functional theory (DFT) calculations found that Pb2+ and Cd2+ ions have the highest adsorption energy on the {001} and {116} facet, respectively, while Hg2+ ions have the largest adsorption energy on the {110} facet. Carved with a variety of facets, such as {012} and {104} facets with weak and even positive adsorption energy, polyhedral NPs show poor adsorption ability and nonselective adsorption toward the three heavy-metal ions selected. Our experimental and computational results not only provide new insights into the facet-related properties, but also guide the design of crystals with exposed active facets for specific applications.

•Novel MWCNT/CdS-DETA photocatalyst was prepared.•MWCNT/CdS-DETA showed high photocatalytic activity.•MWCNT/CdS-DETA showed long reusable life.Designing high performance functional nanomaterials by tuning their dimension at nanoscale and constructing novel interface has been a hot topic in recent years. In this work, multi-walled carbon nanotube (MWCNT)/CdS-diethylenetriamine (DETA) composite photocatalyst was synthesized via hydrothermal method. The structure, morphology, optical property and core level analysis of MWCNT/CdS-DETA nanocomposite were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy spectra (EDS), UV–Vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectrum (XPS). CdS-DETA can be uniformly dispersed on the surface of MWCNT. Photocatalytic properties of as-prepared photocatalysts were investigated under 410 nm LED light irradiation for photodegradation of methylene bule (MB). The kapp of MWCNT/CdS-DETA is 0.034 min−1, which is about 6 times more than pure CdS-DETA. Photostability test indicated that MWCNT/CdS-DETA hybrid can be reused for degradation of organic pollution, suggesting the possible application of MWCNT/CdS-DETA hybrid is the most promising strategy for advanced photocatalyst material design.

Sustainable photocatalytic hydrogen evolution (PHE) of water splitting has been utilized to solve the serious environmental pollution and energy shortage problems over the last decade. Inorganic–organic hybrid materials could combine the organic molecules and functional inorganic blocks into unique materials through complicated physical and chemical interactions. In this paper, diethylenetriamine (DETA) was used as an organic molecule template for the synthesis of inorganic–organic Zn1−xCdxS-DETA solid solution nanoflowers (NFs) at very low temperature. The obtained Zn0.2Cd0.8S-DETA NFs exhibited the highest H2 production rate (12 718 μmol g−1 h−1), which is 1.75 times as high as that of CdS-DETA. The suitable conduction band potential and excellent visible-light absorption of Zn0.2Cd0.8S-DETA solid solution NFs are closely related to the excellent PHE activity. Furthermore, the calculation on the electronic structure provides a new understanding of the band-gap shifts of the Zn1−xCdxS-DETA solid solution hybrids and the design of novel structural photocatalysts.

•Pg-C3N4/BiOBr is successfully synthesized by facile process.•Pg-C3N4/BiOBr shows efficient visible light photocatalytic activity.•Z-scheme photocatalytic mechanism is proposed.Porous graphitic carbon nitride (Pg-C3N4) nanosheets have been prepared via thermal decomposition, and then novel 2D Pg-C3N4/BiOBr hybrid is designed by a facile hydrothermal process. The as-prepared Pg-C3N4/BiOBr hybrids are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–Vis diffuse reflectance spectroscopy (DRS). The results show that BiOBr tightly composited on the surface of Pg-C3N4. Enhanced electron and hole separation efficiency is confirmed by photoluminescence (PL) spectroscopy measurements and the photoelectrochemical evaluation. The photoactivity performance of Pg-C3N4/BiOBr is tested under visible-light irradiation, the result shows that coupling semiconductor of Pg-C3N4/BiOBr apparently enhances the photocatalytic activity. An optimal Pg-C3N4 content has been determined to be 20 wt%, corresponding to apparent pseudo-first-order rate constant kapp of 0.088 min−1, which is 3.7 times, 4.2 times and 7.3 times as high as that of Pg-C3N4, BiOBr and common g-C3N4, respectively. Furthermore, photocatalytic stability and mechanism of enhanced photocatalytic process are also investigated.Novel 2D porous g-C3N4/BiOBr hybrid with enhanced visible-light-driven photocatalytic activity was developed.Download high-res image (137KB)Download full-size image

Morphology control and impurity doping are two widely applied strategies to improve the electrochemical performance of nanomaterials. Herein, we report an environmentally friendly approach to obtain Co-doped Ni(OH)2 nanosheet networks using a laser-induced cobalt colloid as a doping precursor followed by an aging treatment in a hybrid medium of nickel ions. The shape and specific surface area of the doped Ni(OH)2 can be successfully adjusted by changing the concentration of sodium thiosulfate. Furthermore, a Co-doped Ni(OH)2 nanosheet network was further converted into Co-doped NiO with its pristine morphology retained via facile thermal decomposition in air. The structure and electrochemical performance of the as-prepared samples are investigated with scanning and transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, Fourier transform infrared spectroscopy, the nitrogen adsorption–desorption isotherm technique, and electrochemical measurements. The Co-doped Ni(OH)2 electrode shows an ultrahigh specific capacitance of 1421 F g−1 at a current density of 6 A g−1, and a good retention level of 76% after 1000 cycles, in sharp contrast with only a 47% retention level of the pure Ni(OH)2 electrode at the same current density. In addition, the Co-doped NiO electrode exhibits a capacitance of 720 F g−1 at 6 A g−1 and 92% retention after 1000 cycles, which is also superior to the corresponding values of relevant pure NiO electrodes. The Co2+ partially substitutes for Ni2+ in the metal hydroxide and oxide, resulting in an increase of free holes in the valence band, and, therefore, enhancement of the p-type conductivity of Ni(OH)2 and NiO. Moreover, such novel mesoporous nanosheet network structures are also able to enlarge the electrode–electrolyte contact area and shorten the path length for ion transport. The synergetic effect of these two results is responsible for the observed ultrahigh pseudocapacitor performance.

We report the coexistence of resistance switching (RS) behavior and the negative differential resistance (NDR) phenomenon in the α-Fe2O3 nanorod film grown in situ on a fluorine-doped tin oxide glass substrate. The reversible switching of the low- and high-resistance states (LRS and HRS, respectively) of the film device can be excited simply by applying bias voltage. The switching from the HRS to the LRS was initiated in the negative bias region, whereas the NDR process followed by the reversion of the HRS occurred in the positive bias region. With the increase in compliant current (CC), the carrier conduction models of the LRS and the HRS both changed and the current–voltage (I–V) relationships in the NDR region were seriously affected by the thermal process according to the level of applied CC. The co-existence of RS and NDR was possibly caused by defects during migration, such as oxygen vacancies and interstitial iron ions, which were formed in the α-Fe2O3 nanorod film. This work provided information on the ongoing effort toward developing novel electrical features of advanced transition metal oxide devices.

Incorporating noble metal nanoparticles on the surface or the inner side of semiconductors to form a hybrid nanostructure is an effective route for improving the gas sensing performance of the semiconductors. In this study, we present novel Au-decorated ZnO nanospheres (Au–ZnO NSs) obtained by the laser irradiation of liquids. Structural characterization indicated that the Au–ZnO NSs consisted of single crystalline ZnO NSs with a few Au nanoparticles decorated on their surfaces and abundant encapsulated Au nanoparticles with relatively small sizes. Laser irradiation-induced heating–melting–evaporating processes are responsible for the formation of unique Au–ZnO NSs. The gas sensing properties of the Au–ZnO NSs, as gas sensing materials, were investigated and compared with those of pure ZnO NSs. The former showed a lower working temperature, higher sensitivity, better selectivity, and good reproducibility. The response values of the Au–ZnO NS and pure ZnO NS sensors to ethanol of 100 ppm were 252 and 75 at a working temperature of 320 °C and 360 °C, respectively. Significant enhancements in gas sensing performance should be attributed to the electronic sensitization induced by the depleted layers between the encapsulated Au nanoparticles and ZnO and chemical sensitization originating from the catalytic effects of Au nanoparticles decorated on the surfaces that dissociated molecular oxygen.

We present a facile, low-cost procedure by simple one-step combustion of small organic molecules to obtain ultrafine, hydrophobic, and fluorescent carbon nanodots (CNDs). Without further centrifugation and dialysis, we could easily separate CNDs from combustion soot through spontaneous sedimentation. Transmission electron microscopy and photoluminescence characterization demonstrated that the collected CNDs possessed a monodispersed size distribution with a diameter of 1.9 ± 0.5 nm and excitation-independent luminescence properties. Furthermore, after oxidization treatment, the oxidized CNDs displayed good water solubility and the highest fluorescence intensity in neutral solution.

A layered magnesium hydroxide (Mg(OH)2) nanosheet/graphene oxide (GO) composite was synthesized through laser ablation of the Mg target in an aqueous solution with GO. Its mesoporous structure and application as an adsorbent for the removal of methylene blue (MB) and heavy metal ions from water were investigated. Mg(OH)2 nanosheets were organized in situ from the strong reaction between the laser-ablated Mg species and water molecules. The GO nanosheet served as a heterogeneous nucleation and growth site for sheet-like Mg(OH)2 nanocrystals. The resulting porous Mg(OH)2/GO nanosheet composite had a high specific surface area of 310.8 m2 g−1 and a pore volume of 1.031 cm3 g−1. These characteristics show that the composite could be an excellent adsorbent. The composite exhibited a maximum adsorption capacity of 532 mg g−1 at 298 K for typical contaminants of MB, and over 300 mg g−1 for heavy metal ions Zn2+ and Pb2+.

•Laser induced non-stoichiometric SnOx show unique reactivity in aqueous solution of GO.•Photo-excited electrons from semiconductor assisted formation of Pt clusters that in situ dispersed onto SnO2.•The synergetic effect from Pt/SnO2/rGO results in high catalytic activity and long-term durable performance for methanol oxidation.Maximizing the surface area and the exposed active sites of Pt-based catalysts is one of the most effective strategies to improve their electrocatalytic performance. We here present an environmentally friendly construction of a two-dimensional Pt/SnO2/reduced-graphene-oxide (rGO) nanocomposite as a active and durable electrocatalyst. Initially, liquid-phase laser ablation generated highly reactive SnOx nanoparticles (NPs) were used as a precursor to transform the graphene oxide into rGO. Simultaneously, the initial amorphous-like SnOx can further crystallize into SnO2 NPs, which were uniformly anchored onto rGO sheets. Subsequently, the electrons photo-excited from semiconductor SnO2 were used as green reducing agents, which can in situ reduce the PtCl62+ ions to form ultrafine Pt NPs with an average size of about 1–2 nm that uniformly dispersed onto SnO2 NPs. Compared with Pt/rGO catalysts without SnO2 modification, the Pt/SnO2/rGO hybrid ternary catalysts not only show larger electrochemical active surface area and higher catalytic activity toward methanol oxidation, but also exhibit better long-term cycle stability and better tolerance toward CO-like species. Such significantly enhanced electrochemical performance could be attributed to the uniformly dispersed fine Pt NPs and the synergetic effect from the hybrid noble metal-semiconductor-carbon network components.Utilizing the high reactivity of non-stoichiometric SnOx and the photo-excited electrons, Pt clusters can be in situ generated and uniformly anchored on the surface of semiconductor SnO2 to form a rGO supported hybrid catalyst, which present high activity and long-term durable performance for methanol oxidation.

We report a simple and environmentally friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (±0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.Keywords: electrocatalyst; in situ sacrificial template; laser ablation in liquids; methanol oxidation; ultrafine Pt NPs

Nanocomposites can be fabricated in such a way that they retain the advantages but overcome the limitations of each single-material component. Here, we report a convenient route to fabricate MoS2–Co3O4 composites via laser ablation in liquids (LAL) and aging-induced phase transformation. The reactive Co colloids obtained through LAL are used as a non-ion precursor to anchor Co3O4 nanoparticles (NPs) onto the surfaces of MoS2 nanosheets without using any stabilizers. In the fabricated composites, the MoS2 nanosheets serve as a flexible conducting substrate for the in situ phase transformation and crystalline growth of Co3O4 NPs and the network structure of the sheets prevents NPs from further aggregation. Co3O4 NPs not only function as a high-rate capability electrode material but also stabilize the composite structure, thereby generating accessible active surfaces on the MoS2 nanosheets for electrolyte penetration during charging/discharging. The structure and morphology of the as-constructed composites are investigated through scanning and transmission electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. As an active hybrid supercapacitor electrode material, the active composite materials exhibit higher electrochemical performance than either pure MoS2 or pure Co3O4. The superior performance can be attributed to the synergistic effects of the pseudocapacitive reactions from the MoS2 nanosheets and the Faradaic battery reactions of the anchored ultrafine Co3O4 NPs.

Intense scientific efforts have been focused on the exploration of the unusual physical and chemical properties of colloidal nanoparticles (NPs). Here, surfactant-free ablated bismuth colloidal species showing distinctive advantages of high reactivity and reducibility were generated by laser-ablating metal Bi in deionized water. They can further react with water molecules and display self-assembly behaviour to form Bi(OH)3 nanowires at ambient condition. Interestingly, under aging at 60 °C or light irradiation, Bi-based colloids will tend to react and self-assemble into phases of Bi2O3 and Bi2O4 nanocrystals. Furthermore, various bismuth-containing compounds, such as bismuth oxyhalides (BiOX, X = Cl, Br, I), Ag/Au/Pt-modified BiOCl, BiVO4, and Bi2WO6 semiconductors were also successfully produced through the reaction of ablated bismuth colloidal species with corresponding chemical reagents or with ablated V and W colloidal species. These synthetic strategies proved that LAL-induced colloidal species are capable of serving as unique chemical precursors. The relatively slow, dynamic species-by-species reaction greatly favours controllable growth and tunable nanostructure compared with the conventional rapid ion-by-ion reaction. Importantly, this growth route provides more underlying insights regarding the growth and assembly mechanisms of nanocrystals without influence from additional chemical ions or surfactants.

It is important to reduce the recombination of electrons and holes and enhance charge transfer through fine controlled interfaces for advanced catalyst design. In this work, graphene oxide (GO) was composited with graphitic-C3N4 (g-C3N4) and BiOI forming GO/g-C3N4 and GO/BiOI heterostructural interfaces, respectively. GO, which has a work function between the conducting bands of g-C3N4 and BiOI, is used as a buffer material to enhance electron transfer from g-C3N4 to BiOI through the GO/g-C3N4 and GO/BiOI interfaces. The increased photocurrent and reduced photoluminescence indicate efficient reduction of electron and hole recombination under the successful heterostructure design. Accordingly, the introduction of GO as a charge transfer buffer material has largely enhanced the photocatalytic performance of the composite. Thus, introducing charge transfer buffer materials for photocatalytic performance enhancement has proved to be a new strategy for advanced photocatalyst design.

In this paper, we report a rational sandwich composite structure consisting of polyaniline (PANI), amorphous TiO2 (a-TiO2), and a GO network as an anode material for lithium-ion batteries (LIBs). After the synthesis of the a-TiO2–GO composite assisted by laser ablation in liquid, PANI nanorods are vertically grown on the both sides of a-TiO2–GO nanosheets to obtain a stable sandwich structure. The morphology and components of the composites are confirmed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. As a typical anode material in LIBs, the fabricated sandwich composites display a high rate capability and long cycle life. A first discharge capacity of 1335 mA h g−1 is shown at 50 mA g−1 and a reversible capacity of 435 mA h g−1 is achieved after 250 cycles at 100 mA g−1. Even at a high cycling rate of 10 A g−1, the sandwich products exhibit a stable capacity of 141 mA h g−1. This effort highlights the design of a sandwich structure using amorphous TiO2, GO, and PANI nanorods and its potential benefits for LIB application.

We report a facile approach to immobilize magnetic ZnFe2O4 nanoparticles (NPs) onto a reduced grapheme oxide (rGO) network by using highly reactive ZnOx(OH)y and FeOx colloids as precursors, which were respectively obtained by laser ablation of metallic zinc (Zn) and iron (Fe) targets in pure water. A microstructure investigation of such nanocomposites (NCs) revealed that ZnFe2O4 NPs are well-dispersed onto rGO sheets. Such a structure was helpful for separating the photoexcited electron–hole pairs and accelerating the electrons transfer. Electrochemical impedance measurements indicated the remarkable decrease of the interfacial layer resistance of the composite structure compared to that of pure ZnFe2O4 NPs. As a result of these advantages, such NCs present a prominent enhancement in the photodegradation efficiency for methylene blue dye. Besides, the excellent magnetic properties of the ZnFe2O4 NPs allow the catalysts to be easily separated from the solution by a magnet for recycling. This effort not only provided a new approach to fabricate ZnFe2O4–rGO NCs, also expanded the application of ZnFe2O4 NPs used as visible-light excited photocatalysts in application of organic pollutants degradation.

Graphene oxide (GO) in situ composited with MnO2 nanowires was achieved through a hydrothermal process. The morphology and structure of the products were investigated by using field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectra and X-ray diffraction. The results showed that the product consisted of α-MnO2 nanowires with the diameter of 20∼40 nm and the length of 0.5∼2 μm that well dispersed on the surfaces of GO. The excellent electrochemical performance of as-prepared GO/MnO2 hybrids was obtained due to the unique chemical interactions between GO and MnO2. The maximum specific capacitances of 360.3 F/g measured by chronopotentiometry at a current density of 0.5 A/g were obtained in a 1 M Na2SO4 aqueous solution. This value is much higher than that of pure MnO2 nanowire electrodes (128.0 F/g) and commercial MnO2 microparticles electrodes (22.8 F/g). Furthermore, GO/MnO2 nanowires hybrids also exhibit good cycling stability with more than 93% capacitance retention over 1000 cycles. The present synthesis strategy may be readily extended to the preparation of other hybrids based on GO nanosheets for potential applications in energy storage and conversion devices.

Quantum-sized SnO2 nanocrystals can be well dispersed on reduced graphene oxide (rGO) nanosheets through a convenient one-pot in situ reduction route without using any other chemical reagent or source. Highly reactive metastable tin oxide (SnOx) nanoparticles (NPs) were used as reducing agents and composite precursors derived by the laser ablation in liquid (LAL) technique. Moreover, the growth and phase transition of LAL-induced SnOx NPs and graphene oxide (GO) were examined by optical absorption, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy. Highly dispersed SnOx NPs can also prevent rGO from being restacked into a multilayer structure during GO reduction. Given the good electron transfer ability and unsaturated dangling bonds of rGO, as well as the ample electrocatalytic active sites of quantum-sized SnO2 NPs on unfolded rGO sheets, the fabricated SnO2–rGO nanocomposite exhibited excellent performance in the non-enzymatic electrochemical detection of glucose molecules. The use of LAL-induced reactive NPs for in situ GO reduction is also expected to be a universal and environmentally friendly approach for the formation of various rGO-based nanocomposites.

Numerous efforts have been made to integrate nanorods into 3D ordered multifunctional architectures. Herein, we report a rational design and the successful fabrication of a novel chestnut-like Fe3O4@C@ZnSnO3 core–shell hierarchical structure. Reactive Zn and Sn colloids obtained using laser ablation in liquids were used as non-ion precursors to intentionally grow ZnSnO3 nanorods onto the surfaces of core–shell Fe3O4@C particles under solvothermal conditions. The core–shell hierarchical structures were analyzed by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis (EDX), X-ray diffraction, and a superconducting quantum interference device magnetometer (Quantum Design MPMS). The results showed that the Fe3O4@C particles served as nucleation sites for the oriented growth of ZnSnO3 nanorods on the surfaces of the carbon layer. The synthesized core–shell composite exhibited cyclic photocatalytic ability toward the degradation of 2,5-dichlorophenol model molecules because of the compact assembly of the magnetic Fe3O4 core, the active ZnSnO3 photocatalyst, and a protective carbon layer.

Morphology, phase structure and optical performance of ternary surface-fluorinated TiO2 nanosheet/Ag3PO4/Ag composite photocatalysts were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy (DRS). Wide band-gap TiO2 crystal nanosheets were synthesized while stabilizing the {001} facet, which is highly active for oxidation reactions, with fluorination. Narrow band-gap Ag3PO4 crystal was then uniformly grown on a fluorinated-TiO2 nanosheet {001} facet, forming a planar heterojunction between two nanosheet semiconductors. Ag particles were in situ reduced by visible light irradiation from Ag3PO4, forming island-distributed Ag on the Ag3PO4 surface. TiO2/Ag3PO4/Ag exhibited excellent photocatalytic activity and high stability for methylene blue degradation under 410 nm LED light irradiation. The enhanced activities of TiO2/Ag3PO4/Ag could be attributed to effective electron–hole separation, fast hole transportation and the Schottky barrier. This novel ternary TiO2/Ag3PO4/Ag structure material is an ideal candidate in environmental treatment and cleaning applications.

Hematite is an important material used in water splitting and lithium-ion battery electrodes. Electronic conductivity and the visible light-absorption ability of hematite are enhanced by doping impurity ions into the hematite lattice and achieving an appropriate hematite nanostructure. This paper reports the simultaneous doping and growth of tin (Sn)-doped hematite crystalline films on a conducting substrate. The crystalline films were prepared by a hydrothermal process. Laser ablation in liquid induced SnOx colloidal nanoparticles, which were used as the doping source. The obtained compacted films were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and UV-vis spectrophotometry analyses. XRD results showed the Sn-doped α-Fe2O3 crystalline nanoparticles had dominant active (110) planes. Annealing affected the photoelectrochemical (PEC) performance of the Sn-doped hematite photoanode, and the photocurrent density of the photoanode annealed at 750 °C for 2 h reached the highest value at 0.48 mA cm−2 (at 1.23 V vs. reversible hydrogen electrode). Electrochemical impedance spectroscopy measurements revealed that the charge-transfer resistance of Sn-doped hematite films decreased after the annealing treatment. The improved crystallinity and the preferred (110) plane in the doped crystalline film are favor of the migration of electrons and holes to electrode surfaces, the removal of deleterious surface states and increase of the free electron density, which should contribute to the enhanced PEC performance.

•CNT–NiO hybrid nanocomposites were large-scale fabricated.•CNT–NiO presented a high specific capacitance of 759 F g−1.•The obtained CNT–NiO exhibit excellent cycling performance.This study reports an easy chemical conversion route toward large-scale fabrication of carbon nanotube (CNT)–porous nickel oxide (NiO) hybrid nanocomposites as supercapacitor electrode materials. The electrocapacitive performance of CNT–porous NiO hybrids is evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements. The synthesized CNT–NiO hybrid nanocomposite electrode presents a high specific capacitance of 759 F g−1 at 0.5 A g−1 in 6 M KOH aqueous electrolyte, which is almost twice that of pure NiO nanoparticle (388 F g−1) electrodes and nine times of that of commercial NiO particle (88.4 F g−1) electrodes. Furthermore, good capacitance retention is achieved after 1000 cycles of galvanostatic charge–discharge. The synergistic effects from the pseudocapacitance of porous NiO particles, good electrical conductivity, and open tip CNTs attribute to the high capacitance performance.

We developed a new approach to obtain onion-like carbon-encapsulated cobalt carbide (Co3C) core/shell nanoparticles (NPs) by the laser ablation of cobalt in acetone. The as-synthesized core/shell NPs were then characterized by transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, superconducting quantum interference device magnetometer and fluorescence spectrophotometer. TEM observation reveals that the Co3C core is encapsulated by graphitized carbon layers. The number of carbon layers shows certain relationship with the size of the core Co3C NPs. The as-derived core/shell NPs presents unique superparamagnetic property and excitation wavelength-dependent fluorescence. The formation of the carbide and carbon layer can be explained by the laser-induced catalytic cracking of the carbon-rich precursor, acetone molecules. The supersaturated carbon atoms in carbide core tend to be excluded and automatically grow as carbon layers during the subsequent rapid quenching process.

We designed a new strategy, namely, the laser ablation of a target material in an aqueous ionic solution, to prepare Mn-doped Ni(OH)2 nanosheets based on reactions between the pulsed laser-induced plasma plume of Mn and the surrounding NiCl2 solution. The crystalline phase, morphology and structure of the as-derived products are characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Results indicate the hierarchical assembly of numerous tiny nanosheet building blocks into a Mn-doped α-Ni(OH)2 spherical structure. Importantly, the positive electrode made of Mn-doped α-Ni(OH)2 nanosheets exhibits a high specific capacitance of ∼1000 F g−1 under a current density of 5 A g−1, concurrently possessing excellent cycling ability. This novel strategy may offer researchers an alternative for designing interesting solid targets and ionic solutions towards the fabrication of other new nanostructures for fundamental research and potential applications.

We report a self-sacrificed in situ growth design toward preparation of ZnTiO3–TiO2 heterojunction structure. Highly reactive zinc oxide colloidal particles derived by laser ablation in liquids can react with TiO2 nanotubes to form a lamellar ZnTiO3 nanosheet structure in a hydrothermal-treatment process. Such hybrid structural product was characterized by X-ray diffraction, scanning and transmission electron microscopy, UV-vis diffuse reflection spectroscopy and X-ray photoelectron spectroscopy. The enhanced photocatalytic activity of the hybrid structure toward degradation of methyl orange (MO) and pentachlorophenol (PCP) molecules was demonstrated and compared with single phase TiO2, as a result of the efficient separation of light excited electrons and holes at the hetero-interfaces in the two semiconductors.

A TiO2/BiOCl composite with a hierarchical structure was constructed by grafting BiOCl nanosheets onto a film of TiO2 nanotube arrays. The structure and morphology were characterised using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflection spectroscopy, and Raman spectroscopy. The activity of the composite photocatalyst for the photodegradation of methyl orange and pentachlorophenol was higher than that of either single-phase TiO2 or BiOCl. The improved photodecomposition performance can be mainly attributed to the enhanced separation efficiency of photo-induced electrons and holes, both at the interface and in the two semiconductors. The proposed grafting strategy for the formation of this hybrid photocatalyst can also be applied to other semiconductor candidates resulting in improved photo-electrochemical properties.

Nanomaterials have emerged as remarkable photocatalysts. In this report, multifunctional cube-like Zn2SnO4 and urchin-like ZnSnO3 nanomaterials were successfully synthesized using zinc and tin metals as ablation targets by the combined strategy of laser ablation in liquid and hydrothermal treatment. Addition of ammonia to the hydrothermal reaction can not only tune the phase structure of the final products from cubic spinel-type Zn2SnO4 to face-centered perovskite ZnSnO3 but also control the morphology of ZnSnO3 in a concentration-dependent manner. When the ammonia concentration was set to 3.0 mol L−1, uniform urchin-like Zn-deficient ZnSnO3 with remarkable lattice distortion was obtained. Photocatalytic activity tests using methyl orange (MO) and 2,5-dichlorophenol (2,5-DCP) as probe molecules under ultraviolet light excitation demonstrated that urchin-like ZnSnO3 is highly active and effective for the degradation of high concentrations of MO (25 ppm) and 2,5-DCP (10 ppm).

Monodispersed, homogeneous core–shell TaxO@Ta2O5 (x = 1, 2) composite nanoparticles (NPs) are successfully synthesized via one-step liquid phase laser ablation (LPLA) of a tantalum metal plate in ethanol. The morphology, phase structure, and surface states of the core–shell NPs are investigated by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The LPLA-derived spherical-like NPs consist of well-crystallized TaxO cores with diameters of 10–40 nm and amorphous-like Ta2O5 shells with a thickness of ca. 5 nm. A possible formation pathway for TaxO@Ta2O5 core–shell NPs is proposed on the basis of LPLA and subsequent reactive quenching processes. Photocatalytic degradation of methylene blue in the liquid phase serves as a probe reaction to evaluate the activity of the as-prepared core–shell NPs under the irradiation of UV light. Theoretical calculation based on density functional theory indicated the metallic nature of the core TaO phase. Interestingly, compared with pure Ta2O5 powders, the incorporation of suboxide TaxO cores into the shell of Ta2O5 contributes to an enhancement in photocatalytic activity. This work provides new information that may be used for the design and novel application of homogeneous core–shell nanostructures.

The doping of foreign atoms is critical in tailoring the properties and potential applications of semiconductor nanocrystals. A general strategy for successfully incorporating various impurities (e.g., Ge, Si, Mn, Sn, Ti) inside the regular crystal lattice of hematite (α-Fe2O3), a promising candidate for water splitting and environmental protection, is developed. Liquid-phase laser ablation-derived colloidal clusters are used as doping precursors for the metastable growth of doped hematite nanocrystals, thereby avoiding surfactants and hazardous liquid byproducts. The doping percentage, morphology, and structure of the hematite nanocrystals are greatly affected by the type and amount of the colloidal precursors used. High-resolution transmission electron microscopy and the corresponding component analysis reveal that the dopant atoms either form superlattice structures (Ge and Si) or distribute as disordered solid solutions (Mn, Sn, Ti) inside the crystal lattice of hematite. The optical absorption spectra and the resulting band gaps of the doped-hematite nanocrystals are investigated. Typical electronic transitions consisting of ligand to metal charge transitions, Fe3+ d–d transitions, and pair excitations distinctly occur in the optical spectra. The simultaneous incorporation of impurities and preferential growth mechanism of hematite nanocrystals are also further elaborated.

A novel strategy was designed to prepare Ag cluster-doped TiO2 nanoparticles (Ag/TiO2 NPs) without addition of any chemical reducing agent and/or organic additive. A defect-rich TiOx species was generated by laser ablation in liquid (LAL) of a Ti target. The silver ions could be reduced and deposited on the surface of TiO2 NPs through the removal of oxygen vacancies and defects; the TiOx species evolved into anatase NPs in a hydrothermal treatment process. The derived Ag/TiO2 NPs are approximately 25 nm in size, with narrow size distribution. The Ag clusters are highly dispersed inside TiO2 and less than 3 nm in size. The doped amount can be tuned by changing the concentration of Ag+ ions. The as-synthesized Ag/TiO2 NPs display improved photocatalytic efficiency toward pentachlorophenol (PCP) degradation.

Reactive non-stoichiometric tin oxide (SnOx) nanoparticles were facilely obtained by laser ablation of Sn in water using a fundamental nanosecond pulse laser. The size of the primary nanoparticles increased and the crystallinity spontaneously improved without heat treatment when the colloidal solutions were aged in the dark. Interestingly, such ageing-induced self-crystallization processes were considerably different from those in the colloidal solution illuminated by sunlight and/or ultraviolet light. Both the primary amorphous SnOx nanoparticles and the aged nanocrystals were used for water purification; the contaminants studied included methyl orange, methylene blue, pentachlorophenol, and dichromate. All removal treatments produced good results, and had high degradation rates. Comparison with experimental investigations revealed that nanoparticles synthesized using conventional methods, such as sol–gel synthesis, showed poor performance or had no effect on the removal of water contaminants. In contrast, SnOx nanoparticles derived by laser ablation in liquid possessed high surface reactivity, and the corresponding aged nanocrystals exhibited enhanced photocatalytic activity compared with commercial SnO2 nanoparticles. These materials may be used in wastewater purification.

Decoration of TiO2 by metal nanoparticles allows for the fabrication of a new nanocomposite electrode with enhanced performance in photo-electrochemical applications. In this article, we report a facile way to synthesize free-standing, highly orientated TiO2 nanotube (TiO2-NT) arrays by a new kind of two-step electrochemical anodization method, and an efficient decoration of uniform sized Ag nanoparticles onto the outer and inner surface of TiO2 nanotubes through a wetting-thermal decomposition route. In particular, compared with pure TiO2-NT arrays, the testing of nanoelectrode made with Ag/TiO2-NTs composite arrays presents enhanced efficiency in photocatalytic degradation of methylene blue dye and organic pollutant of pentachlorophenol, and improved electrochemical responses as results of the suppression of electron/hole pairs from recombination and acceleration of surface charge transfer by Ag nanoparticles.

We report a universal strategy for doping hematite photoanode materials. Si-doped hematite nanosheets with a superlattice structure were first synthesised by hydrothermal treatment of a mixture of FeCl3 agent and liquid phase laser ablation-derived-silicon colloids. The dopant site in Si-doped hematite was clarified at the atomic scale.

The liquid-phase laser ablation of solid targets may create new materials and structures as a result of unique reactions and the rapid quenching of a liquid-confined plasma plume with features of high temperature and pressure. We demonstrated here the formation of novel nanostructures by laser ablation of a Ti plate in de-ionized water. When the pulse laser is focused on a fixed tiny spot on the target surface during ablation, Ti@TiO2 core-shell nanoparticles (NPs) can be obtained. The crystalline metal core was a metastable faced-centered-cubic (fcc) phase of Ti; while the Ti plate was being rotated, the pulse laser interacted with different spots on the metal surface in one circle and only amorphous TiO2 species could be found. Toward the synthesis of hierarchical titanate nanostructures, the unique colloidal suspensions obtained by laser ablation were further hydrothermally treated in alkaline solutions. The TiO2 NPs synthesized from the rotated Ti target could form titanate hierarchical spheres by self-assembly of nanostripes. The core-shell Ti@TiO2 NPs initially formed titanate nanostripes assembled hierarchical spheres, however, with increasing duration time these spheres with Ti cores would separate and reorganize into fibers, which evolved into single crystalline nanoribbons, and ultimately grew into long rod-like hierarchical nanostructures. Both the titanate hierarchical spheres and the corresponding calcined spheres presented high photocatalytic activity in the degradation of a trace amount of pentachlorophenol.

We report a simple and green strategy to organize Mn3O4 nanoparticles into single-crystalline γ-MnOOH nanowires on the basis of hydrothermal treatment of the colloids induced by laser ablation in water. Evidence obtained from a transmission electron microscopy investigation revealed that the organization mainly involved the following steps: nanoparticles → polycrystalline nanochains → single crystalline nanowires.

A plasma plume consisting of metal ions and atoms induced by laser ablation of metal Zn can react strongly with the molecules it encounters in liquid solutions. We report the liquid-phase laser ablation-induced synthesis of ZnO nanoparticles and layered zinc hydroxide/dodecyl sulfate (ZnHDS) hybrid nanosheets using a fundamental 1064-nm nanosecond laser. A large amount of ZnHDS nanosheets, together with a small amount of Zn nanospheres and ZnO nanoparticles, could be produced from sodium dodecyl sulfate (SDS) solutions. Thermally induced vaporization of Zn species is favorable for the formation of ZnHDS nanosheets in SDS solutions and ZnO nanoparticles in pure water, while the explosive boiling and ejection of melting Zn droplets is responsible for the formation of sphere-like Zn particles. Photoluminescence measurements of ensemble or individual ablated products reveal that hybrid ZnHDS nanosheets assembled from metastable β-Zn(OH)2 and DS− ions show strong blue and green luminescence under UV-light excitation.Graphical abstractHighlights► Zn species generated by laser ablation in liquids can react strongly with encountered H2O for forming metastable β-Zn(OH)2, which then proceeding charging-assemble with SDS molecules. We report first the assembled layered zinc hydroxide/dodecyl sulfate hybrid nanosheets presents strong and stable blue and green luminescence.

We present a clean synthesis of well-crystallized pure Mn3O4 nanoparticles by pulsed laser ablation of an Mn metal plate immersed in deionized water at room temperature. The particle size, phase structure, and magnetic properties are characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectra, and superconducting quantum interference device. The colloids solution of Mn3O4 nanocrystals with narrow particles size distribution could be facile obtained in a single step without addition of any other chemical reagents. As-synthesized pure manganese oxide nanoparticles show good performance in significant and rapid removal of trace amounts of pentachlorophenol. Thoroughly distinct from the general chemical process for growing manganese oxide nanoparticles, here the formation of manganese oxide nanocrystalline is based on reactions between laser-generated manganese species and water molecules in a local high-temperature and high-pressure plume−liquid interface region.

Nanomaterials have emerged as remarkable photocatalysts. In this report, multifunctional cube-like Zn2SnO4 and urchin-like ZnSnO3 nanomaterials were successfully synthesized using zinc and tin metals as ablation targets by the combined strategy of laser ablation in liquid and hydrothermal treatment. Addition of ammonia to the hydrothermal reaction can not only tune the phase structure of the final products from cubic spinel-type Zn2SnO4 to face-centered perovskite ZnSnO3 but also control the morphology of ZnSnO3 in a concentration-dependent manner. When the ammonia concentration was set to 3.0 mol L−1, uniform urchin-like Zn-deficient ZnSnO3 with remarkable lattice distortion was obtained. Photocatalytic activity tests using methyl orange (MO) and 2,5-dichlorophenol (2,5-DCP) as probe molecules under ultraviolet light excitation demonstrated that urchin-like ZnSnO3 is highly active and effective for the degradation of high concentrations of MO (25 ppm) and 2,5-DCP (10 ppm).

It is important to reduce the recombination of electrons and holes and enhance charge transfer through fine controlled interfaces for advanced catalyst design. In this work, graphene oxide (GO) was composited with graphitic-C3N4 (g-C3N4) and BiOI forming GO/g-C3N4 and GO/BiOI heterostructural interfaces, respectively. GO, which has a work function between the conducting bands of g-C3N4 and BiOI, is used as a buffer material to enhance electron transfer from g-C3N4 to BiOI through the GO/g-C3N4 and GO/BiOI interfaces. The increased photocurrent and reduced photoluminescence indicate efficient reduction of electron and hole recombination under the successful heterostructure design. Accordingly, the introduction of GO as a charge transfer buffer material has largely enhanced the photocatalytic performance of the composite. Thus, introducing charge transfer buffer materials for photocatalytic performance enhancement has proved to be a new strategy for advanced photocatalyst design.

We designed a new strategy, namely, the laser ablation of a target material in an aqueous ionic solution, to prepare Mn-doped Ni(OH)2 nanosheets based on reactions between the pulsed laser-induced plasma plume of Mn and the surrounding NiCl2 solution. The crystalline phase, morphology and structure of the as-derived products are characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Results indicate the hierarchical assembly of numerous tiny nanosheet building blocks into a Mn-doped α-Ni(OH)2 spherical structure. Importantly, the positive electrode made of Mn-doped α-Ni(OH)2 nanosheets exhibits a high specific capacitance of ∼1000 F g−1 under a current density of 5 A g−1, concurrently possessing excellent cycling ability. This novel strategy may offer researchers an alternative for designing interesting solid targets and ionic solutions towards the fabrication of other new nanostructures for fundamental research and potential applications.

Reactive non-stoichiometric tin oxide (SnOx) nanoparticles were facilely obtained by laser ablation of Sn in water using a fundamental nanosecond pulse laser. The size of the primary nanoparticles increased and the crystallinity spontaneously improved without heat treatment when the colloidal solutions were aged in the dark. Interestingly, such ageing-induced self-crystallization processes were considerably different from those in the colloidal solution illuminated by sunlight and/or ultraviolet light. Both the primary amorphous SnOx nanoparticles and the aged nanocrystals were used for water purification; the contaminants studied included methyl orange, methylene blue, pentachlorophenol, and dichromate. All removal treatments produced good results, and had high degradation rates. Comparison with experimental investigations revealed that nanoparticles synthesized using conventional methods, such as sol–gel synthesis, showed poor performance or had no effect on the removal of water contaminants. In contrast, SnOx nanoparticles derived by laser ablation in liquid possessed high surface reactivity, and the corresponding aged nanocrystals exhibited enhanced photocatalytic activity compared with commercial SnO2 nanoparticles. These materials may be used in wastewater purification.

We report a universal strategy for doping hematite photoanode materials. Si-doped hematite nanosheets with a superlattice structure were first synthesised by hydrothermal treatment of a mixture of FeCl3 agent and liquid phase laser ablation-derived-silicon colloids. The dopant site in Si-doped hematite was clarified at the atomic scale.

Quantum-sized SnO2 nanocrystals can be well dispersed on reduced graphene oxide (rGO) nanosheets through a convenient one-pot in situ reduction route without using any other chemical reagent or source. Highly reactive metastable tin oxide (SnOx) nanoparticles (NPs) were used as reducing agents and composite precursors derived by the laser ablation in liquid (LAL) technique. Moreover, the growth and phase transition of LAL-induced SnOx NPs and graphene oxide (GO) were examined by optical absorption, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy. Highly dispersed SnOx NPs can also prevent rGO from being restacked into a multilayer structure during GO reduction. Given the good electron transfer ability and unsaturated dangling bonds of rGO, as well as the ample electrocatalytic active sites of quantum-sized SnO2 NPs on unfolded rGO sheets, the fabricated SnO2–rGO nanocomposite exhibited excellent performance in the non-enzymatic electrochemical detection of glucose molecules. The use of LAL-induced reactive NPs for in situ GO reduction is also expected to be a universal and environmentally friendly approach for the formation of various rGO-based nanocomposites.

Incorporating noble metal nanoparticles on the surface or the inner side of semiconductors to form a hybrid nanostructure is an effective route for improving the gas sensing performance of the semiconductors. In this study, we present novel Au-decorated ZnO nanospheres (Au–ZnO NSs) obtained by the laser irradiation of liquids. Structural characterization indicated that the Au–ZnO NSs consisted of single crystalline ZnO NSs with a few Au nanoparticles decorated on their surfaces and abundant encapsulated Au nanoparticles with relatively small sizes. Laser irradiation-induced heating–melting–evaporating processes are responsible for the formation of unique Au–ZnO NSs. The gas sensing properties of the Au–ZnO NSs, as gas sensing materials, were investigated and compared with those of pure ZnO NSs. The former showed a lower working temperature, higher sensitivity, better selectivity, and good reproducibility. The response values of the Au–ZnO NS and pure ZnO NS sensors to ethanol of 100 ppm were 252 and 75 at a working temperature of 320 °C and 360 °C, respectively. Significant enhancements in gas sensing performance should be attributed to the electronic sensitization induced by the depleted layers between the encapsulated Au nanoparticles and ZnO and chemical sensitization originating from the catalytic effects of Au nanoparticles decorated on the surfaces that dissociated molecular oxygen.

We report the coexistence of resistance switching (RS) behavior and the negative differential resistance (NDR) phenomenon in the α-Fe2O3 nanorod film grown in situ on a fluorine-doped tin oxide glass substrate. The reversible switching of the low- and high-resistance states (LRS and HRS, respectively) of the film device can be excited simply by applying bias voltage. The switching from the HRS to the LRS was initiated in the negative bias region, whereas the NDR process followed by the reversion of the HRS occurred in the positive bias region. With the increase in compliant current (CC), the carrier conduction models of the LRS and the HRS both changed and the current–voltage (I–V) relationships in the NDR region were seriously affected by the thermal process according to the level of applied CC. The co-existence of RS and NDR was possibly caused by defects during migration, such as oxygen vacancies and interstitial iron ions, which were formed in the α-Fe2O3 nanorod film. This work provided information on the ongoing effort toward developing novel electrical features of advanced transition metal oxide devices.

Decoration of TiO2 by metal nanoparticles allows for the fabrication of a new nanocomposite electrode with enhanced performance in photo-electrochemical applications. In this article, we report a facile way to synthesize free-standing, highly orientated TiO2 nanotube (TiO2-NT) arrays by a new kind of two-step electrochemical anodization method, and an efficient decoration of uniform sized Ag nanoparticles onto the outer and inner surface of TiO2 nanotubes through a wetting-thermal decomposition route. In particular, compared with pure TiO2-NT arrays, the testing of nanoelectrode made with Ag/TiO2-NTs composite arrays presents enhanced efficiency in photocatalytic degradation of methylene blue dye and organic pollutant of pentachlorophenol, and improved electrochemical responses as results of the suppression of electron/hole pairs from recombination and acceleration of surface charge transfer by Ag nanoparticles.

We report a self-sacrificed in situ growth design toward preparation of ZnTiO3–TiO2 heterojunction structure. Highly reactive zinc oxide colloidal particles derived by laser ablation in liquids can react with TiO2 nanotubes to form a lamellar ZnTiO3 nanosheet structure in a hydrothermal-treatment process. Such hybrid structural product was characterized by X-ray diffraction, scanning and transmission electron microscopy, UV-vis diffuse reflection spectroscopy and X-ray photoelectron spectroscopy. The enhanced photocatalytic activity of the hybrid structure toward degradation of methyl orange (MO) and pentachlorophenol (PCP) molecules was demonstrated and compared with single phase TiO2, as a result of the efficient separation of light excited electrons and holes at the hetero-interfaces in the two semiconductors.

Morphology control and impurity doping are two widely applied strategies to improve the electrochemical performance of nanomaterials. Herein, we report an environmentally friendly approach to obtain Co-doped Ni(OH)2 nanosheet networks using a laser-induced cobalt colloid as a doping precursor followed by an aging treatment in a hybrid medium of nickel ions. The shape and specific surface area of the doped Ni(OH)2 can be successfully adjusted by changing the concentration of sodium thiosulfate. Furthermore, a Co-doped Ni(OH)2 nanosheet network was further converted into Co-doped NiO with its pristine morphology retained via facile thermal decomposition in air. The structure and electrochemical performance of the as-prepared samples are investigated with scanning and transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, Fourier transform infrared spectroscopy, the nitrogen adsorption–desorption isotherm technique, and electrochemical measurements. The Co-doped Ni(OH)2 electrode shows an ultrahigh specific capacitance of 1421 F g−1 at a current density of 6 A g−1, and a good retention level of 76% after 1000 cycles, in sharp contrast with only a 47% retention level of the pure Ni(OH)2 electrode at the same current density. In addition, the Co-doped NiO electrode exhibits a capacitance of 720 F g−1 at 6 A g−1 and 92% retention after 1000 cycles, which is also superior to the corresponding values of relevant pure NiO electrodes. The Co2+ partially substitutes for Ni2+ in the metal hydroxide and oxide, resulting in an increase of free holes in the valence band, and, therefore, enhancement of the p-type conductivity of Ni(OH)2 and NiO. Moreover, such novel mesoporous nanosheet network structures are also able to enlarge the electrode–electrolyte contact area and shorten the path length for ion transport. The synergetic effect of these two results is responsible for the observed ultrahigh pseudocapacitor performance.