Electrochemical water-splitting provides an effective strategy to convert electrical energy into renewable energy resource. In this work, we report a bifunctional gas-evolving fibrous electrode based on nonprecious heterostructured Ni@NiO wrapped carbon fiber (CF) for overall water-splitting reaction. The proposed Ni@NiO wrapped CF (CF@Ni@NiO) was fabricated through a simple and controllable electrodeposition and subsequent low-temperature calcination procedure, which can easily be scaled up for practical use. Benefitting from the exposed heterojunction-like Ni@NiO nanointerfaces and the formation of Ni (III) species, the resultant CF@Ni@NiO electrode exhibits excellent catalytic activity, favorable kinetics, as well as strong durability toward both cathodic hydrogen evolution reactions (HER) and anodic oxygen evolution reactions (OER) in alkaline electrolyte, with an overall water-splitting current of 20 mA cm–2 at 1.73 V (iR uncorrected), which outperforms that of other reported nonprecious electrocatalysts. Moreover, owing to their intrinsic mechanical flexibility, these fibrous gas-evolving electrodes can be readily woven into textile structures for practical applications. The simple, low-cost, and scalable fabrication process of heterostructured materials modified fibrous electrode, coupled with recent progress in nonprecious electrocatalysts for both HER and OER, offers the possibilities to systematically study the dependence of catalytic performance on the structural parameters of the electrocatalysts, which also open new horizon for the development of next-generation flexible water-splitting devices.Keywords: Bifunctional electrodes; Carbon fiber; Electrocatalysis; Nickel/nickel oxide; Water splitting;

In this work, we report the development of well-ordered hydrogenated CoMoO4 (H-CoMoO4) and hydrogenated Fe2O3 (H-Fe2O3) nanoplate arrays on 3D graphene foam (GF) and explore their practice application as binder-free electrodes in assembling flexible all-solid-state asymmetric supercapacitor (ASC) devices. Our results show that the monolithic 3D porous GF prepared by solution casting method using Ni foam template possesses large surface area, superior electrical conductivity, and sufficient surface functional groups, which not only facilitate in situ growth of CoMoO4 and Fe2O3 nanoplates but also contribute the double-layer capacitance of the resultant supercapacitor. The well-ordered pseudocapacitive metal oxide nanoplate arrays standing up on 3D GF scaffold can provide efficient space and shorten the length for electrolyte diffusion from the outer to the inner region of the electrode material for Faradaic energy storage. Furthermore, one of our major findings is that the introduction of oxygen vacancies in CoMoO4 and Fe2O3 nanoplates by hydrogenation treatment can increase their electronic conductivity as well as improve their donor density and surface properties, which gives rise to a substantially improved electrochemical performance. Benefiting from the synergistic contributions of different components in the nanohybrid electrode, the resultant flexible ASC device with GF/H-CoMoO4 as the positive electrode and GF/H-Fe2O3 as the negative electrode achieves a wide operation voltage of 1.5 V and a maximum volumetric specific capacitance of 3.6 F cm–3, which is two times larger than that of the Ni/GF/CoMoO4//Ni/GF/Fe2O3 device (1.8 F cm–3), and the rate capability is up to 70% as the current density increases from 2 to 200 mA cm–3. Moreover, the Ni/GF/H-CoMoO4//Ni/GF/H-Fe2O3 device also exhibits a high energy density of 1.13 mWh cm–3 and a high power density of 150 mW cm–3, good mechanical flexibility with the decrease in capacitance of less than 4% after being bent inward to different angles and inward to 90° 200 times, and good cycling stability of 93.1% capacitance retention after 5000 cycles.Keywords: all-solid-state asymmetric supercapacitor; binder-free flexible electrode; hydrogenated transition-metal oxide; ordered nanoplate arrays; three-dimensional graphene foam;

The development of active and stable metal-based catalysts are highly desired in chemical transformation. As is known, the catalytic activity and durability of supported catalyst are strongly dependent on the morphology of supporting material and the size distribution of metal nanoparticles (NPs). We report the fabrication of a high-performance nitrogen-doped carbon tubes@Pd (NCT@Pd) catalyst, in which well-dispersed ultrafine Pd NPs were deposited onto N-doped carbon microtubular support. Due to the synergy effect between the permeable mesoporous NCT shell and anchored ultrafine Pd NPs, the resultant NCT@Pd tubular catalyst shows remarkably high activity toward the reduction of 4-nitrophenol with a turnover frequency (TOF) of 29.5 min−1, even when the loading amount of active Pd NPs is as low as 0.324 wt%. Furthermore, NCT@Pd can also be applied for Suzuki coupling reaction with a TOF up to 44.0 min−1.Download high-res image (180KB)Download full-size image

The development of efficient, low-cost, and durable electrocatalysts toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting associated with renewable energy conversion and storage. Carbon-based nanomaterials have been widely employed as electrocatalysts for the independent HER or OER; however, research on bifunctional metal-free electrocatalysts for water splitting is still in its infancy and remains a formidable challenge to develop highly active catalysts for future applications. Here we report a highly active defect-rich, carbon-based, bifunctional metal-free water splitting electrocatalyst, prepared by a template approach, in which a nitrogen-enriched polydopamine analogue is used as the carbon precursor. The resultant defect-rich porous carbon (DRPC) exhibits a large specific surface area with a hierarchically micro/mesoporous structure and a high nitrogen doping content with rich pyridinic N. Accordingly, the newly developed DRPC electrocatalysts display superb bifunctional catalytic activities for both the HER and the OER in alkaline solution, outperforming all other reported metal-free catalysts. Significantly, the DRPC catalyst couple-based alkaline water electrolyzer with strong durability delivers a 10 mA cm−2 overall water splitting current at a considerably low voltage of 1.74 V, and a demonstration of a self-powered electrochemical water splitting system is also presented, highlighting its great potential for practical applications.

Supercapacitors based on transition-metal-oxide (TMO) offer an attractive option owing to their high energy densities, low cost of materials, high abundance, environmental-friendliness and corrosion-resistance. Despite extensive research efforts, the development of TMO-based supercapacitors still falls short of the expectations largely because of their poor conductivity, low rate capability and charge/discharge characteristics. Here, a solid-state thin-film asymmetric supercapacitor (ASC) based on highly conductive TMO was fabricated by regulating the microstructure of electrode materials. This design minimizes the electronic and ionic resistance and produces an ASC with ultrafast rate capability (up to 150 V s−1) and fast frequency response (relaxation time constant τ0 = 10.2 ms), which substantially surpasses the previously reported values for solid-state TMO-based supercapacitors and most carbon-based flexible micro-supercapacitors. Furthermore, the state-of-the-art ASC demonstrates long cycle stability (97% of capacitance retention after 10 000 cycles), high energy density (0.14 mW h cm−3) and power density (12.30 W cm−3), which are comparable with those of certain commercial supercapacitors and carbon-based micro-supercapacitors.

A bioinspired polydopamine derivative was prepared by self-polymerization of 6-(2-aminoethyl)-3-hydroxypyridin-2(1H)-one (AHPO) in an alkaline aqueous medium. It was used as a precursor to produce nanocapsules of pyridinic N-rich carbon with a desired N doping content by using silica nanoparticles as the template. These N-doped nanocapsules exhibited superior electrocatalytic activity and stability towards the oxygen reduction reaction (ORR), lending an attractive alternative to the Pt catalyst. This work provides an important insight into the rational designing of bioinspired polymers for the development of functional carbon materials with excellent properties.

The development of high performance non-platinum electrocatalysts is highly desirable for the commercialization of fuel cells. Herein, we present a facile and effective strategy for the synthesis of ultrafine PdCo bimetallic nanoparticles (NPs, diameter ≈ 4.1 nm) encapsulated in N-doped porous carbon nanocapsules (PdCo@NPNCs) by a one-pot PdCl42− and Co2+-mediated polymerization of dopamine on SiO2 nanospheres, followed by carbonization and chemical etching. The N-doped porous carbon shell that is formed in situ from a dopamine coating could effectively prevent the coalescence of NPs during the carbonization process. Also the carbon shell protects the NPs from detachment and agglomeration as well as dissolution during fuel cell operation. Benefiting from the synergistic effect from their unique structures and chemical compositions, the optimized PdCo@NPNCs exhibit better electrocatalytic activity and enhanced durability for the oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR) in alkaline solution than those of commercial Pt/C (20 wt%) and Pd/C (10 wt%) catalysts, even though the content of PdCo is as low as 3.68 wt%. Furthermore, the synthetic method described here can be generalized to other bimetallic NPs confined in NPNCs that can be used in a broad range of applications such as catalysis, environmental protection, drug delivery, chemical and biological sensing, and so forth.

Although carbonaceous materials possess long cycle stability and high power density, their low-energy density greatly limits their applications. On the contrary, metal oxides are promising pseudocapacitive electrode materials for supercapacitors due to their high-energy density. Nevertheless, poor electrical conductivity of metal oxides constitutes a primary challenge that significantly limits their energy storage capacity. Here, an advanced integrated electrode for high-performance pseudocapacitors has been designed by growing N-doped-carbon-tubes/Au-nanoparticles-doped-MnO2 (NCTs/ANPDM) nanocomposite on carbon fabric. The excellent electrical conductivity and well-ordered tunnels of NCTs together with Au nanoparticles of the electrode cause low internal resistance, good ionic contact, and thus enhance redox reactions for high specific capacitance of pure MnO2 in aqueous electrolyte, even at high scan rates. A prototype solid-state thin-film symmetric supercapacitor (SSC) device based on NCTs/ANPDM exhibits large energy density (51 Wh/kg) and superior cycling performance (93% after 5000 cycles). In addition, the asymmetric supercapacitor (ASC) device assembled from NCTs/ANPDM and Fe2O3 nanorods demonstrates ultrafast charge/discharge (10 V/s), which is among the best reported for solid-state thin-film supercapacitors with both electrodes made of metal oxide electroactive materials. Moreover, its superior charge/discharge behavior is comparable to electrical double layer type supercapacitors. The ASC device also shows superior cycling performance (97% after 5000 cycles). The NCTs/ANPDM nanomaterial demonstrates great potential as a power source for energy storage devices.

Recent advances in flexible fiber-based microelectrodes have opened a new horizon for sensitive real-time near-cell and even intracellular measurements. In this work, we develop a new type of hierarchical nanohybrid microelectrode based on three-dimensional (3D) porous graphene-wrapped activated carbon fiber (ACF) via a facile and effective electrodeposition of graphene oxide (GO) nanosheets on ACF using a green ionic liquid (IL) as the electrolyte. This technique enables the simultaneous electrodeposition and electrochemical reduction of GO nanosheets on ACF to form 3D porous IL functionalized electrochemically reduced GO (ERGO)-wrapped ACF (IL–ERGO/ACF). The adsorbed IL molecules on the ERGO surface provide sufficient active sites and act as the template for the in situ electrodeposition of highly dense and well-dispersed bimetal PtAu nanoflowers on the 3D IL–ERGO scaffold. By virtue of the unique array of structural and chemical properties of bimetal PtAu nanocatalysts and 3D porous IL–ERGO on ACF, the resultant PtAu nanoflowers-decorated IL–ERGO/ACF (PtAu/IL–ERGO/ACF) microelectrode demonstrates a variety of excellent sensing performances, including high sensitivity, a wide linear range and good selectivity in the electrochemical detection of a newly emerged cancer biomarker, hydrogen peroxide (H2O2). When used for the real-time tracking of H2O2 secreted from female cancer cells, such as breast cancer cells and gynecological cancer cells, the electrochemical sensor based on the PtAu/IL–ERGO/ACF microelectrode provides important information for distinguishing between different cancer cells and normal cells and for evaluating the therapeutic activity of antitumor drugs towards live cancer cells, which are of great clinical significance for cancer diagnosis and management.

A fiber-based multifunctional nickel phosphide (NiPx) electrode has been successfully prepared by facile electrodeposition of nickel nanoparticle arrays on a commercial carbon fiber (CF) followed by low-temperature phosphidation. As a result of the synergistic effect from the 3D porous structure, enhanced conductivity, and the two active components Ni2+ and Pδ− with rich valences, the resulting vertically aligned NiPx nanoflakes grown on the CF (CF@NiPx) electrode exhibit superior bifunctional electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in an alkaline electrolyte as well as an ultrahigh specific volumetric capacitance of 817 F cm−3 at a current density of 2 mA cm−2. For practical applications, an efficient CF@NiPx-based alkaline water electrolyzer, with strong durability, can achieve 10 mA cm−2 water-splitting current at a cell voltage of only 1.61 V (iR uncorrected). Besides, a fiber-based flexible solid-state asymmetric supercapacitor device with CF@NiPx as the cathode and reduced graphene oxide attached on CF@Ni (CF@Ni@RGO) as the anode was observed to achieve a remarkable volumetric energy density of 8.97 mW h cm−3, excellent flexibility and superior long term cycling stability. All these results render our fiber-based CF@NiPx electrodes as an ideal platform for electrocatalysis and flexible electrochemical energy storage applications.

A novel donor–acceptor–donor–acceptor (D–A1–D–A2) π-conjugated copolymer (PDBPyDT2FBT) has been prepared by Stille coupling reaction. It is found that PDBPyDT2FBT exhibits low LUMO energy level mainly because of multiple electron-deficient units and donor–acceptor interaction, which is favorable to obtain more efficient electron injection and transport in organic thin-film transistors (OTFTs). Moreover, introducing two electron-deficient moieties into the thiophene-containing copolymer increases the length of conjugated main chain and enhances the coplanarity of the backbone, which may be beneficial for promoting the molecular crystallinity and improving molecular ordering capability at low temperatures. High electron and hole mobilities up to 0.65 and 0.24 cm2 V –1 s–1 were obtained at relatively low annealing temperatures of 100 and 80 °C, respectively, implying that PDBPyDT2FBT is a promising ambipolar polymer semiconductor applied in low-cost and large-area manufacturing of OTFTs.Keywords: ambipolar; annealing temperature; donor−acceptor−donor−acceptor copolymer; electron mobility; hole mobility; OTFT

The development of carbon based hollow-structured nanospheres (HNSs) materials has stimulated growing interest due to their controllable structure, high specific surface area, large void space, enhanced mass transport, and good biocompatibility. The incorporation of functional nanomaterials into their core and/or shell opens new horizons in designing functionalized HNSs for a wider spectrum of promising applications. In this work, we report a new type of functionalized HNSs based on Pd nanoparticles (NPs) decorated double shell structured N-doped graphene quantum dots (NGQDs)@N-doped carbon (NC) HNSs, with ultrafine Pd NPs and “nanozyme” NGQDs as dual signal-amplifying nanoprobes, and explore their promising application as a highly efficient electrocatalyst in electrochemical sensing of a newly emerging biomarker, i.e., hydrogen peroxide (H2O2), for cancer detection. Due to the synergistic effect of the robust and conductive HNS supports and catalytically active Pd NPs and NGQD in facilitating electron transfer, the NGQD@NC@Pd HNS hybrid material exhibits high electrocatalytic activity toward the direct reduction of H2O2 and can promote the electrochemical reduction reaction of H2O2 at a favorable potential of 0 V, which effectively restrains the redox of most electroactive species in physiological samples and eliminates interference signals. The resultant electrochemical H2O2 biosensor based hybrid HNSs materials demonstrates attractive performance, including low detection limit down to nanomole level, short response time within 2 s, as well as high sensitivity, reproducibility, selectivity, and stability, and have been used in real-time tracking of trace amounts of H2O2 secreted from different living cancer cells in a normal state and treated with chemotherapy and radiotherapy.Keywords: cancer detection; carbon hollow nanospheres; electrocatalyst; electrochemical biosensor; graphene quantum dots; Pd nanoparticles

•3D ZNs/ADM electrodes synthesized via CV based on the first-principle calculation.•ZNs/ADM electrodes exhibit ultrahigh capacitive performance.•ASC based on ZNs/ADM electrode exhibits high energy density and power density.•The doped Au atoms and distributed Au NPs enhanced electrochemical performance.Poor electrical conductivity of metal oxides is the primary challenge that limits their energy storage capacity. Intercalating metal atoms into the crystal lattices of metal oxides are expected to change the electronic structure of metal oxides, and thus improve the conductivity as well as electrochemical performance of the metal oxides. Herein, we demonstrate the doping of α-MnO2 nanocrystallines by Au through Å-scale channels via cyclic voltammetry at different scan rates on the basis of first-principle calculation. Experiments elucidate that the doped Au atoms in α-MnO2 lattice and distributed Au nanoparticles in α-MnO2 nanothin layers can greatly enhance the conductivity and electrochemical performance of MnO2. Hence, the designed carbon cloth electrodes modified with ZnO-nanorods/Au-doped-α-MnO2 (ZNs/ADM) nanocomposites exhibit excellent electrochemical performances. Moreover, an asymmetric supercapacitor based on ZNs/ADM (positive) and reduced-graphene-oxide-CNTs (negative) hybrid materials demonstrates cycled reversibly in a wide potential window and exhibits high energy density (101 W h/kg), power density (33.6 kW/kg), and reasonable cycling performance. This work opens the possibility to develop new types of metal-doped metal-oxides that can meet the needs of specific applications, ranging from energy-storage devices to biosensors.

A new copolymer (P(DPP4T-co-BDT)) was synthesized by Stille coupling polymerization of 3,6-bis(5′-bromo-[2,2′-bithiophen]-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]-pyrrole-1,4(2H,5H)-dione and 2,6-bis(trimethyltin)-4,8-dimethoxybenzo[1,2-b:3,4-b′]dithiophene. P(DPP4T-co-BDT) showed good solution processability, good thermal stability with decomposition temperature of >330 °C, and strong and broad absorption in the range of 500–900 nm. Field-effect transistors based on P(DPP4T-co-BDT) thin films exhibited a hole mobility of up to 0.047 cm2 V−1 s−1, an on/off current ratio of 106, and a threshold voltage of −5 V after thermal annealing at 200 °C. Thin film phototransistors based on P(DPP4T-co-BDT) exhibited a photoresponsivity of up to 4.0 × 103 A W−1 and a photocurrent/dark-current ratio of 6.8 × 105 under white light irradiation with a low light intensity (9.7 μW cm−2).

A three-dimensional graphene wrapped nickel foam (Ni/GF) architecture has been prepared by a facile yet effective and scalable interfacial reduction method. Inspired by the porous and conductive network structures of Ni/GF, we have deposited manganese dioxide (MnO2) and polypyrrole (PPy) nanostructures on the Ni/GF substrates and successfully fabricated a flexible solid-state asymmetric supercapacitor assembled with Ni/GF/MnO2 as the positive electrode and Ni/GF/PPy as the negative electrode in a gel electrolyte. Benefiting from the high capacitance and fast ion transport properties of our hierarchically porous electrodes, the optimized asymmetric supercapacitor exhibits an excellent stability in a high-voltage region of 1.8 V and remarkable cycling stability with only 9.8% decrease of capacitance after 10000 cycles. Moreover, the device can deliver a high energy density of 1.23 mW h cm−3, which is substantially enhanced compared to most of the reported solid-state supercapacitors. The impressive results presented here may pave the way for promising applications in future energy storage systems.

Recent progress in fiber-based supercapacitors has attracted tremendous attention due to the tiny volume, high flexibility and weavability of the fibers, which are required for the development of high-performance fiber electrodes. In this work, we report for the first time, the design and fabrication of two types of core–shell fiber-based electrodes, i.e. hierarchically structured manganese dioxide (MnO2)/graphene/carbon fiber (CF) and three-dimensional (3D) porous graphene hydrogel (GH) wrapped copper wire (CW), and their practical application in a fiber-architectured flexible all-solid-state supercapacitor. Taking advantage of the synergistic effects of the different components in the hierarchically structured nanohybrid fiber electrodes and the merits of the proposed synthesis strategies, the assembled asymmetric supercapacitor device using MnO2/graphene/CF as the positive electrode and GH/CW as the negative electrode could be cycled reversibly in a high-voltage region of 0–1.6 V, delivering a high areal energy density of 18.1 μW h cm−2 and volumetric energy density of 0.9 mW h cm−3. Furthermore, our fiber-based flexible supercapacitor also shows a good rate capability, excellent flexibility and high long term cyclability, which makes it a promising power source for flexible energy-related devices.

An ultra-low Pd loading nanocatalyst is synthesized by a convenient solution route of photochemical reduction and aqueous chemical growth. The modification of nanocatalyst structures is investigated through changing morphologies of Pd nanoclusters on the surface of ZnO nanorods. A significant enhancement in photocatalytic properties has been achieved by decorating a trace amount of Pd clusters (0.05 at%) on the surface of ZnO nanorods. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) is applied to demonstrate multiple catalytic activities in the Pd–ZnO hybrid nanocatalyst, which also provides a better understanding of the relationship between the unique nanoconfigured structure and catalytic performance.

Fiber based supercapacitors are promising energy storage devices for flexible electronics because of their integration of lightweight, high flexibility and tiny volume. Here, a facile yet effective method is developed to synthesize two types of functionalized carbonaceous fibers, i.e., carbon fiber@reduced graphene oxide@manganese dioxide (CF@RGO@MnO2) and CF@thick RGO (CF@TRGO), by dip coating and subsequent electrochemical strategies. The assembled asymmetric supercapacitor device using CF@RGO@MnO2 as the positive electrode and CF@TRGO as the negative electrode can be operated with a high voltage region of 1.6 V and exhibits a high volumetric energy density of 1.23 mW h cm−3. Additionally, our device has an excellent long-term cycling stability with more than 91% retention after 10000 cycles. To demonstrate potential applications of our prepared fiber based all-solid-state asymmetric supercapacitors, we successfully use them to power a flexible integrated copper phthalocyanine (CuPc) photodetector and a light-emitting diode.

Recent progress in the in situ molecular detection of living cells has attracted tremendous research interests due to its great significance in biochemical, physiological, and pathological investigation. Especially for the electrochemical detection of hydrogen peroxide (H2O2) released by living cells, the highly efficient and cost-effective electrocatalysts are highly desirable. In this work, we develop a novel type of microporous Co3O4 hollow nanospheres containing encapsulated Pd nanoparticles (Pd@Co3O4). Owing to the synergy effect between the permeable microporous Co3O4 shell and the ultrafine Pd nanoparticles that encapsulated in it, the resultant Pd@Co3O4 based electrode exhibits excellent electrochemical sensor performance toward H2O2, even when the content of Pd in Pd@Co3O4 hollow nanospheres is as low as 1.14 wt %, which enable it be used for real-time tracking of the secretion of H2O2 in different types of living human cells.Keywords: biosensors; electrochemistry; living cell tracking; microporous hollow nanospheres; ultrafine Pd nanoparticles

Three-dimensional (3D) graphene/carbon nanotube (CNT)/SnO2 (GCS) hybrid architectures were constructed by a facile and cost-effective self-assembly method through hydrothermal treatment of a mixture of Sn2+, CNTs, and graphene oxide (GO). The resultant GCS displayed a 3D hierarchically porous structure with large surface area and excellent electrical conductivity, which could effectively prevent the aggregation and volume variation of SnO2 and accelerate the transport of ions and electrons through 3D pathways. Benefiting from the unique structure and the synergistic effect of different components in the hybrid architectures, the GCS exhibited a remarkably improved reversible capacity of 842 mAh g–1 after 100 cycles at 0.2 A g–1 and excellent rate performance for lithium storage compared with that of graphene/SnO2 (GS) hybrid architectures. Hence, the impressive results presented here could provide a universal platform for fabricating graphene/CNT-based hybrid architectures with promising applications in various fields.Keywords: carbon nanotubes; graphene; hybrid architectures; lithium ion batteries; one-pot synthesis; SnO2

A unique Pd nanoparticle loaded hierarchically porous graphene network was successfully prepared through multiple synergistic interactions. The obtained architectures as electrocatalysts exhibit significantly higher activity and durability for ethanol oxidation than commercial Pd/C catalysts.

A multifunctional magnetic 3D graphene/Fe3O4 architecture (GFA) has been fabricated by a facile and scalable one-pot self-assembled strategy through hydrothermal treatment of a mixed aqueous precursor solution of graphene oxide (GO) and Fe3O4 nanoparticles (NPs). Benefiting from the 3D porous structure and synergistic effects of the assembled graphene nanosheets and Fe3O4 NPs, the resultant GFA exhibits excellent adsorption capacities of not only organic dyes such as methylene blue (MB), but also toxic solvents such as toluene and chloroform, and improved electrochemical capacitive performances in comparison with pristine graphene architectures and Fe3O4 NPs. The impressive results presented here may have high impact on the future fabrication of functional graphene based architectures for practical applications.

Freestanding paper-like electrode materials have trigged significant research interest for their practical application in flexible and lightweight energy storage devices. In this work, we reported a new type of flexible nanohybrid paper electrode based on full inkjet printing synthesis of a freestanding graphene paper (GP) supported three-dimensional (3D) porous graphene hydrogel (GH)–polyaniline (PANI) nanocomposite, and explored its practical application in flexible all-solid-state supercapacitor (SC). The utilization of 3D porous GH scaffold to load nanostructured PANI dramatically enhances the electrical conductivity, the specific capacitance and the cycle stability of the GH–PANI nanocomposite. Additionally, GP can intimately interact with GH–PANI through π–π stacking to form a unique freestanding GP supported GH–PANI nanocomposite (GH–PANI/GP) with distinguishing mechanical, electrochemical and capacitive properties. These exceptional attributes, coupled with the merits of full inkjet printing strategy, lead to the formation of a high-performance binder-free paper electrode for flexible and lightweight SC application. The flexible all-solid-state symmetric SC based on GH–PANI/GP electrode and gel electrolyte exhibits remarkable mechanical flexibility, high cycling performance and acceptable energy density of 24.02 Wh kg–1 at a power density of 400.33 W kg–1. More importantly, the proposed simple and scale-up full inkjet printing procedure for the preparation of freestanding GP supported 3D porous GH-PANI nanocomposite is a modular approach to fabricate other graphene-based nanohybrid papers with tailorable properties and optimal components.Keywords: all-solid-state supercapacitor; flexible electrode; freestanding graphene paper; full inkjet printing synthesis; three-dimensional porous graphene−polyaniline nanocomposite

We reported the development of a new type of bifunctional nanocatalyst based on three-dimensional (3D) macroscopic carbon nanotube (CNT)–graphene hydrogel (GH) supported Pd nanoparticles (i.e., Pd–CNT–GH) and explored its practical application in catalytic reduction of p-nitrophenol to p-aminophenol. The 3D Pd–CNT–GH was synthesized by a facile one-pot self-assembled approach through hydrothermal treatment of a mixed aqueous precursor solution of PdCl42–, CNT, and graphene oxide (GO). Under the appropriate condition, the spontaneous redox reaction between precursor PdCl42– and CNT–GO as well as the self-assembly of macroscopic CNT–GH occurs simultaneously, leading to the formation of 3D Pd–CNT–GH. Because of the unique structural and functional properties of different components in the nanocatalyst and the synergistic effect between them, the as-prepared Pd–CNT–GH exhibits superior catalytic performance toward the reduction of p-nitrophenol to p-aminophenol, with 100% conversion within 30 s, even when the content of Pd in it is as low as 2.98 wt %. Moreover, after 20 successive cycles of reactions, the reaction time still keeps within 46 s. Therefore, the rational design of 3D macroscopic graphene-based nanohybrid material supported highly catalytically active nanoparticles, combined with the facile one-pot self-assembled strategy, provide a universal platform to fabricate desired 3D multifunctional nanomaterials that can be used in a broad range of catalysis, environmental protection, energy storage and conversation, drug delivery, chemical and biological sensing, and so forth.Keywords: carbon nanotube; catalysis; graphene hydrogel; one-pot self-assembly; p-nitrophenol; palladium nanoparticles

We reported the development of a new type of multifunctional titanium dioxide (TiO2)-graphene nanocomposite hydrogel (TGH) by a facile one-pot hydrothermal approach and explored its environmental and energy applications as photocatalyst, reusable adsorbents, and supercapacitor. During the hydrothermal reaction, the graphene nanosheets and TiO2 nanoparticles self-assembled into three-dimensional (3D) interconnected networks, in which the spherical nanostructured TiO2 nanoparticles with uniform size were densely anchored onto the graphene nanosheets. We have shown that the resultant TGH displayed the synergistic effects of the assembled graphene nanosheets and TiO2 nanoparticles and therefore exhibited a unique collection of physical and chemical properties such as increased adsorption capacities, enhanced photocatalytic activities, and improved electrochemical capacitive performance in comparison with pristine graphene hydrogel and TiO2 nanoparticles. These features collectively demonstrated the potential of 3D TGH as an attractive macroscopic device for versatile applications in environmental and energy storage issues.Keywords: adsorbents; graphene hydrogel; photocatalyst; self-assembly; supercapacitor; titanium dioxide nanoparticles;

A unique Pd nanoparticle loaded hierarchically porous graphene network was successfully prepared through multiple synergistic interactions. The obtained architectures as electrocatalysts exhibit significantly higher activity and durability for ethanol oxidation than commercial Pd/C catalysts.

A bioinspired polydopamine derivative was prepared by self-polymerization of 6-(2-aminoethyl)-3-hydroxypyridin-2(1H)-one (AHPO) in an alkaline aqueous medium. It was used as a precursor to produce nanocapsules of pyridinic N-rich carbon with a desired N doping content by using silica nanoparticles as the template. These N-doped nanocapsules exhibited superior electrocatalytic activity and stability towards the oxygen reduction reaction (ORR), lending an attractive alternative to the Pt catalyst. This work provides an important insight into the rational designing of bioinspired polymers for the development of functional carbon materials with excellent properties.

A new copolymer (P(DPP4T-co-BDT)) was synthesized by Stille coupling polymerization of 3,6-bis(5′-bromo-[2,2′-bithiophen]-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo-[3,4-c]-pyrrole-1,4(2H,5H)-dione and 2,6-bis(trimethyltin)-4,8-dimethoxybenzo[1,2-b:3,4-b′]dithiophene. P(DPP4T-co-BDT) showed good solution processability, good thermal stability with decomposition temperature of >330 °C, and strong and broad absorption in the range of 500–900 nm. Field-effect transistors based on P(DPP4T-co-BDT) thin films exhibited a hole mobility of up to 0.047 cm2 V−1 s−1, an on/off current ratio of 106, and a threshold voltage of −5 V after thermal annealing at 200 °C. Thin film phototransistors based on P(DPP4T-co-BDT) exhibited a photoresponsivity of up to 4.0 × 103 A W−1 and a photocurrent/dark-current ratio of 6.8 × 105 under white light irradiation with a low light intensity (9.7 μW cm−2).

A three-dimensional graphene wrapped nickel foam (Ni/GF) architecture has been prepared by a facile yet effective and scalable interfacial reduction method. Inspired by the porous and conductive network structures of Ni/GF, we have deposited manganese dioxide (MnO2) and polypyrrole (PPy) nanostructures on the Ni/GF substrates and successfully fabricated a flexible solid-state asymmetric supercapacitor assembled with Ni/GF/MnO2 as the positive electrode and Ni/GF/PPy as the negative electrode in a gel electrolyte. Benefiting from the high capacitance and fast ion transport properties of our hierarchically porous electrodes, the optimized asymmetric supercapacitor exhibits an excellent stability in a high-voltage region of 1.8 V and remarkable cycling stability with only 9.8% decrease of capacitance after 10000 cycles. Moreover, the device can deliver a high energy density of 1.23 mW h cm−3, which is substantially enhanced compared to most of the reported solid-state supercapacitors. The impressive results presented here may pave the way for promising applications in future energy storage systems.

Recent progress in fiber-based supercapacitors has attracted tremendous attention due to the tiny volume, high flexibility and weavability of the fibers, which are required for the development of high-performance fiber electrodes. In this work, we report for the first time, the design and fabrication of two types of core–shell fiber-based electrodes, i.e. hierarchically structured manganese dioxide (MnO2)/graphene/carbon fiber (CF) and three-dimensional (3D) porous graphene hydrogel (GH) wrapped copper wire (CW), and their practical application in a fiber-architectured flexible all-solid-state supercapacitor. Taking advantage of the synergistic effects of the different components in the hierarchically structured nanohybrid fiber electrodes and the merits of the proposed synthesis strategies, the assembled asymmetric supercapacitor device using MnO2/graphene/CF as the positive electrode and GH/CW as the negative electrode could be cycled reversibly in a high-voltage region of 0–1.6 V, delivering a high areal energy density of 18.1 μW h cm−2 and volumetric energy density of 0.9 mW h cm−3. Furthermore, our fiber-based flexible supercapacitor also shows a good rate capability, excellent flexibility and high long term cyclability, which makes it a promising power source for flexible energy-related devices.

Fiber based supercapacitors are promising energy storage devices for flexible electronics because of their integration of lightweight, high flexibility and tiny volume. Here, a facile yet effective method is developed to synthesize two types of functionalized carbonaceous fibers, i.e., carbon fiber@reduced graphene oxide@manganese dioxide (CF@RGO@MnO2) and CF@thick RGO (CF@TRGO), by dip coating and subsequent electrochemical strategies. The assembled asymmetric supercapacitor device using CF@RGO@MnO2 as the positive electrode and CF@TRGO as the negative electrode can be operated with a high voltage region of 1.6 V and exhibits a high volumetric energy density of 1.23 mW h cm−3. Additionally, our device has an excellent long-term cycling stability with more than 91% retention after 10000 cycles. To demonstrate potential applications of our prepared fiber based all-solid-state asymmetric supercapacitors, we successfully use them to power a flexible integrated copper phthalocyanine (CuPc) photodetector and a light-emitting diode.

A fiber-based multifunctional nickel phosphide (NiPx) electrode has been successfully prepared by facile electrodeposition of nickel nanoparticle arrays on a commercial carbon fiber (CF) followed by low-temperature phosphidation. As a result of the synergistic effect from the 3D porous structure, enhanced conductivity, and the two active components Ni2+ and Pδ− with rich valences, the resulting vertically aligned NiPx nanoflakes grown on the CF (CF@NiPx) electrode exhibit superior bifunctional electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in an alkaline electrolyte as well as an ultrahigh specific volumetric capacitance of 817 F cm−3 at a current density of 2 mA cm−2. For practical applications, an efficient CF@NiPx-based alkaline water electrolyzer, with strong durability, can achieve 10 mA cm−2 water-splitting current at a cell voltage of only 1.61 V (iR uncorrected). Besides, a fiber-based flexible solid-state asymmetric supercapacitor device with CF@NiPx as the cathode and reduced graphene oxide attached on CF@Ni (CF@Ni@RGO) as the anode was observed to achieve a remarkable volumetric energy density of 8.97 mW h cm−3, excellent flexibility and superior long term cycling stability. All these results render our fiber-based CF@NiPx electrodes as an ideal platform for electrocatalysis and flexible electrochemical energy storage applications.

The development of high performance non-platinum electrocatalysts is highly desirable for the commercialization of fuel cells. Herein, we present a facile and effective strategy for the synthesis of ultrafine PdCo bimetallic nanoparticles (NPs, diameter ≈ 4.1 nm) encapsulated in N-doped porous carbon nanocapsules (PdCo@NPNCs) by a one-pot PdCl42− and Co2+-mediated polymerization of dopamine on SiO2 nanospheres, followed by carbonization and chemical etching. The N-doped porous carbon shell that is formed in situ from a dopamine coating could effectively prevent the coalescence of NPs during the carbonization process. Also the carbon shell protects the NPs from detachment and agglomeration as well as dissolution during fuel cell operation. Benefiting from the synergistic effect from their unique structures and chemical compositions, the optimized PdCo@NPNCs exhibit better electrocatalytic activity and enhanced durability for the oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR) in alkaline solution than those of commercial Pt/C (20 wt%) and Pd/C (10 wt%) catalysts, even though the content of PdCo is as low as 3.68 wt%. Furthermore, the synthetic method described here can be generalized to other bimetallic NPs confined in NPNCs that can be used in a broad range of applications such as catalysis, environmental protection, drug delivery, chemical and biological sensing, and so forth.

Supercapacitors based on transition-metal-oxide (TMO) offer an attractive option owing to their high energy densities, low cost of materials, high abundance, environmental-friendliness and corrosion-resistance. Despite extensive research efforts, the development of TMO-based supercapacitors still falls short of the expectations largely because of their poor conductivity, low rate capability and charge/discharge characteristics. Here, a solid-state thin-film asymmetric supercapacitor (ASC) based on highly conductive TMO was fabricated by regulating the microstructure of electrode materials. This design minimizes the electronic and ionic resistance and produces an ASC with ultrafast rate capability (up to 150 V s−1) and fast frequency response (relaxation time constant τ0 = 10.2 ms), which substantially surpasses the previously reported values for solid-state TMO-based supercapacitors and most carbon-based flexible micro-supercapacitors. Furthermore, the state-of-the-art ASC demonstrates long cycle stability (97% of capacitance retention after 10000 cycles), high energy density (0.14 mW h cm−3) and power density (12.30 W cm−3), which are comparable with those of certain commercial supercapacitors and carbon-based micro-supercapacitors.