To improve the efficiency of cobalt-based catalysts for water electrolysis, tremendous efforts have been dedicated to tuning the composition, morphology, size, and structure of the materials. We report here a facile preparation of orthorhombic CoTe2 nanocrystals embedded in an N-doped graphitic carbon matrix to form a 3D architecture with a size of ∼500 nm and abundant mesopores of ∼4 nm for the oxygen evolution reaction (OER). The hybrid electrocatalyst delivers a small overpotential of 300 mV at 10 mA cm–2, which is much lower than that for pristine CoTe2 powder. After cycling for 2000 cycles or driving continual OER for 20 h, only a slight loss is observed. The mesoporous 3D architecture and the strong interaction between N-doped graphitic carbon and CoTe2 are responsible for the enhancement of the electrocatalytic performance.Keywords: cobalt telluride; mesoporous architecture; metal−organic framework; N-doped graphitic carbon; oxygen evolution reaction;

Rational design of hierarchical nanostructure arrays as integrated electrodes with the capability of storing energy has been studied extensively. However, a low electronic/ionic transport rate and structural instability hampered their practical application. In this study, we have fabricated carbon-sheathed NiMoO4 nanowires standing on nickel foam (NF) and employed as a free-standing electrode for supercapacitor. The unique structure revealed remarkable electrochemical behavior including a high areal capacitance, ∼70% capacitance retention at 100 mA cm–2, and an stability during cycling (86% retention after 50,000 cycles). In addition, an NF@NiMoO4@C//activated carbon hybrid supercapacitor presents 201.3 F g–1 of specific capacitance along with an 72.4 W h kg–1 of energy density. The carbon sheath, which prevents the structural pulverization of NiMoO4 and provides another conductive path together with Ni foam, is responsible for the superior electrochemical performances. Our work demonstrates an improved step toward rational design of high-performance integrated electrodes for a supercapacitor with a new vision for theoretical and practical applications.Keywords: Carbon; Integrated electrode; Ni foam; NiMoO4; Supercapacitor;

Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA)2(MA)n−1PbnI3n+1 (BA = CH3(CH2)3NH3+, MA = CH3NH3+) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as “n = 4”, are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

Clean Pt nanoclusters with a diameter of 1.0–2.4 nm, supported on reduced graphene oxide (rGO) nanosheets, were successfully synthesized by simple in situ thermolysis of a Pt-carbonyl complex. The supported Pt nanoclusters are in an electron-deficient state because of the electron transfer between the nanoclusters and the rGO sheets. The as-prepared Pt-1 nm/rGO shows high catalytic activity for the 100% selective hydrogenation of nitrobenzene, with the turnover frequency (TOF) reaching 975.4 h−1 at 25°C and 1 atm. This number is higher than the previously reported value for the heterogeneously catalyzed hydrogenation of nitrobenzene. The proposed process follows a direct hydrogenation mechanism, as is revealed by the analyses of the intermediate products. This work presents a facile and effective synthetic approach for achieving highly efficient nanocatalysts, and can be extended to obtain other metal catalysts with ultra-small sizes and excellent performance.本文以羰基铂为前驱体, 采用简便的原位热解方法, 成功地合成了负载在还原氧化石墨烯(rGO)纳米片上的直径为1.0–2.4 nm的清洁Pt纳米团簇. 由于Pt纳米团簇和rGO片之间的电子转移, 所制备的负载Pt纳米团簇处于缺电子状态. 在25°C、1 atm下, 制备的Pt纳米团簇-1 nm/rGO催化剂的硝基苯选择性加氢的转换频率(TOF)达到975.4 h−1. 这个数值是目前硝基苯的非均相催化氢化所报道的活性最高值. 此外, 根据中间产物分析, Pt-1 nm/rGO催化硝基苯加氢的机理是直接氢化. 这项工作在构筑高效催化剂方面提供了一个简单有效的途径, 并且可以进一步扩展制备其他具有超小尺寸和卓越性能的金属催化剂.

•One-step solvothermal method to synthesize CoSe2/carbon paper catalytic electrode.•CoSe2 nanosheets on carbon paper as highly efficient electrochemical water splitting catalyst.•The interlayer of CoSe2 was expanded to offer more electroactive site.Water splitting associated with the conversion and storage of renewable energy is considered to be the most significant strategy to create hydrogen. Herein, an efficient self-supported electrode was developed by in-situ growth of interlayer expanded lamellar cobalt diselenide (CoSe2) nanosheets (NS) on carbon paper (CP) substrate (CoSe2 NS@CP). The analyses of TEM, SEM and XRD confirmed that the CP is homogeneously coated by few stacking layers of interlayer expanded lamellar structured CoSe2. This rationally designed nanostructure can provide more active sites for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The bifunctional electrode exhibits high electrocatalytic performance with −128 mV vs. RHE onset potential for the HER in 0.5 mol dm−3 H2SO4 and +1521 mV vs. RHE for the OER in 1.0 mol dm−3 KOH. Besides, small electrolysis potentials of −201.1 mV vs. RHE and +1636 mV vs. RHE are needed to drive the HER and OER at current density of 100 mA cm−2. Finally, a small overall cell voltage (ca. +1.75 V) was used to drive the water splitting reaction in 1.0 mol dm−3 KOH. The CoSe2 NS@CP electrode showed both excellent catalytic activity with overall current density of 100 mA cm−2 at 2.13 V and tremendous durability with negligible decrease in potential at a constant current of 20 mA cm−2 for more than 30 hours. Thus this rationally designed electrode material can be readily applied for large-scale water splitting process.Download high-res image (300KB)Download full-size image

•A novel 2D material black phosphorus was used to construct Ni2P-based catalyst.•The Ni2P/BP catalyst exhibits excellent activity and stability for HER.•The strong synergistic effect contributes to the high catalytic activity.•This study provides guidance for designing novel hybrid in electrocatalysis.Nickel phosphide-based nanomaterials have been acted as efficient catalysts for the hydrogen evolution reaction (HER), however, the design of novel and high performance HER catalyst is still a challenge. Herein, we report a novel 2D material black phosphorus (BP) as support for constructing Ni2P-based hybrid catalyst by a one-pot thermal decomposition approach. TEM results indicated that the monodispersed Ni2P nanoparticles with small size and good dispersion supported on the surface of layered BP, which implied that more catalytic active sites may be exposed for HER. The as-synthesized Ni2P/BP hybrid exhibits high HER electrocatalytic performance with low onset overpotential (70 mV), small Tafel slope (81 mV dec−1), large double-layer capacitance (1.24 mF cm−2), high conductivity and good stability, which can be assigned to the strong synergistic effect between Ni2P and BP. Therefore, BP may be a suitable support for constructing excellent catalysts in electrocatalysis.Download high-res image (407KB)Download full-size image

The construction of efficient and low-cost bimetallic phosphide catalysts for hydrogen evolution is still in challenge. In this work, a series of porous Co–Mo phosphide nanotubes which are synthesized via in situ phosphidation process of CoMoO4 nanorods precursor at different phosphatization temperature have been used for hydrogen evolution reaction (HER). X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy and N2 adsorption–desorption experiments were used to characterize the as-synthesized Co–Mo phosphide nanotubes. Results indicate that the phosphatization temperature is the key factor in the formation process of tube-like structure. The possible formation mechanism of Co–Mo phosphide nanotubes was further proposed. Additionally, the as-synthesized CoMoP-600 nanotubes displayed the highest HER catalytic performance and long-time durability in 0.5 M H2SO4 solution. The high catalytic performance of CoMoP-600 catalyst may be attributed to the favorable composition and the large surface area. This study shines a light in the application of bimetallic catalysts for the HER and provides us a new way to design and synthesize porous hollow tube-like structure materials.

•A novel ternary heterostructured nanofiber mat is proposed.•The nanofiber mat can be directly used as anode electrodes for flexible LIBs.•Remarkable electrochemical performances can keep continuity.•Synergic effects of CNFs, TiO2 nanoshells and MoS2 nanosheets were studied.The requirements of high power density, excellent cycling ability, flexibility and low cost, are of paramount importance and critical to develop flexible lithium ion batteries (LIBs) for wearable instruments. Here we reported the rational design and fabrication of a flexible self-supported lithium ion anode material, which consists of thin MoS2 nanosheets grown on the surfaces of carbon@TiO2 core-shell nanofibers. The resulting hierarchical ternary nanocomposites exhibited high reversible specific capacity (∼1460 mA h g−1 at 100 mA g−1), excellent cyclability (little capacity loss even after 1000 cycles) and rate performance (928 mA h g−1 at 2 A g−1) as anode in LIB. Furthermore, the binder-free anode material demonstrated new opportunities for flexible lithium ion batteries. The superior lithium storage performance is derived from the present well-designed hierarchical nanofiber structure and the synergic effect of different components and numerous interfaces.Hierarchical self-supported carbon@TiO2-MoS2 nanofiber mats have been designed as an anode material for lithium ion batteries, which exhibited an ultrahigh specific capacity, stability and excellent flexibility due to their well-defined hierarchical nanostructures and synergetic effects of the components. The highly flexible mats also facilitate the fabrication of flexible LIBs, meaning the promising applications in the portable electronic devices.Download high-res image (205KB)Download full-size image

•Ni2P NPs decorated NPPC was achieved by in-situ thermal decomposition process.•Ni2P/NPPC showed the best HER activity due to synergistic and co-doped effects.•Combined HER experiment and structure characteristic, the mechanism is deduced.•This study provides a new way to design Ni2P-based HER electrocatalysts.The design of efficient and robust Ni2P-based hybrid catalysts for hydrogen evolution reaction (HER) is still in challenge. In this work, a hybrid catalyst composed of monodispersed Ni2P nanoparticles (NPs) and N, P co-doped porous carbon (NPPC) was synthesized through a facile thermal decomposition and used as an efficient electrocatalyst for the HER in 0.5 M H2SO4 solution. Series technologies including X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 sorption are used to characterize the as-synthesized catalysts. The electrochemisty experiments suggested that the as-synthesized Ni2P/NPPC displayed efficient electrocatalytic performance with a low onset overpotential (51 mV), small Tafel slope (74 mV dec−1), high exchange current density (0.12 mA cm−2), large electrochemical double-layer capacitance (21.97 mF cm−2) and high conductivity for the HER. The needed overpotentials are 159 and 184 mV to reach to the current density of 10 and 20 mA cm−2, respectively. Simultaneously, Ni2P/NPPC also displayed good stability in acid solution. The more defects and active sites on the porous carbon which are offered by the co-doped N and P atoms as well as the synergistic effect between NPPC and Ni2P NPs are contributed to the excellent catalytic performance for HER. The current study suggests that introducing the N, P heteroatoms co-doped carbon materials to the Ni2P-based catalysts could enhance HER electrocatalytic performance efficiently.Download high-res image (107KB)Download full-size image

We report a mild synthetic method to access Sn nanocrystals with tunable diameter and narrow size distribution (6–8%). The self-templated formation of various types of Sn chalcogenide hollow nanostructures including oxides, sulfides, selenides, and tellurides is also demonstrated for the first time. The use of air-stable tungsten hexacarbonyl that produces carbon monoxide at elevated temperature to reduce the SnCl2 precursor and coordinate the nanoparticle surface is thought to play an essential role in this method. This synthesis method is likely to be extended to other metal systems and could find potential applications including battery anodes and catalysts.

The development of visible-light-responsive photocatalysts is a promising challenge in the management of environmental pollution. Silver–silver halide nano-photocatalysts have received intensive attention due to their excellent photocatalytic performance in recent years, where silver nanoparticles/nanoclusters demonstrate plasmonic enhanced light absorption efficiency and have been considered as an important component in various functional photocatalytic nanocomposite materials, serving for harvesting visible light. This review provides an overall survey on the state-of-the-art silver–silver halide-based photocatalysts, fundamental understanding of their plasmonically induced photo-reactions and their major environmental applications. We first discuss the basic concepts of localized surface plasmon resonance, and outline the general mechanism of silver–silver halide-based photocatalysis. We then discuss the latest progress in the design and fabrication of silver halide based photocatalysis using various strategies. Next, we highlight some selected examples to demonstrate the new applications of silver/silver halide nano-photocatalysts. Eventually, we provide an outlook of the present challenges and some perspectives of new directions in this interesting and emerging research area.

•Layer expanded MoS2 nanosheet.•Hydrothermal synthesis of MoS2/CF nanocomposite.•Efficient HER electrocatalyst.Molybdenum disulfide (MoS2) has become a promising electrochemical catalyst for reduction of protons to hydrogen in the so-called hydrogen evolution reaction (HER). In order to increase the HER activity, a huge effort has been made to design MoS2 catalysts with affording more active sites and higher conductivity. In this paper, an efficient HER electrochemical catalyst has been developed through an in-situ reduction of ammonium tetrathiomolybdate (ATTM) on carbon fibers (CFs) to afford layer-expanded MoS2/CFs composites (LE-MoS2/CFs). X-ray diffraction (XRD) indicates the interlayer of MoS2 nanosheets was expanded with d spacing 9.9 Å, and transmission electron microscopy (TEM) shows the lattice distance as 0.99 nm, which is agreed with XRD data. The HER test shows that the LE-MoS2/CFs with Mo/C molar ratio of 0.04 has the highest catalytic activity with the lowest overpotential (131 mV vs. RHE) and the highest current density (10 mA cm−2 at 200 mV vs. RHE), owing to a balance between the numbers of exposed active edge sites of MoS2 and fast transport paths for electrons provided by CFs.

In a perovskite solar cell, the overall photoinduced charge-transfer (CT) process comprises both charge diffusion through the bulk to perovskite/electrode interfaces and interfacial electron and hole transfer to electrodes. In this study, we decoupled these two entangled processes by investigating the film thickness-dependent CT dynamics from CH3NH3PbI3 perovskites to [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) (electron acceptor) and spiro-OMeTAD (hole acceptor). By fitting ultrafast transient absorption kinetics to an explicit “diffusion-coupled charge-transfer” model, we found that the charge diffusion from the film interior to perovskite/electrode interfaces took ∼200 ps to a few nanoseconds, depending on the thickness of perovskite film; the subsequent interfacial charge transfer was ultrafast, ∼6 ps for electron transfer to PCBM and ∼8 ps for hole transfer to spiro-OMeTAD, and led to efficient charge extraction (>90%) to electrodes in a 400 nm thick film. Our results indicate that the picosecond interfacial charge transfer is a key to high-performance perovskite solar cells.

The design of efficient artificial photosynthetic systems that harvest solar energy to drive the hydrogen evolution reaction via water reduction is of great importance from both the theoretical and practical viewpoints. Integrating appropriate co-catalyst promoters with strong light absorbing materials represents an ideal strategy to enhance the conversion efficiency of solar energy in hydrogen production. Herein, we report, for the first time, the synthesis of a class of unique hybrid structures consisting of ultrathin Co(Ni)-doped MoS2 nanosheets (co-catalyst promoter) intimately grown on semiconductor CdS nanorods (light absorber). The as-synthesized one-dimensional CdS@doped-MoS2 heterostructures exhibited very high photocatalytic activity (with a quantum yield of 17.3%) and stability towards H2 evolution from the photoreduction of water. Theoretical calculations revealed that Ni doping can increase the number of uncoordinated atoms at the edge sites of MoS2 nanosheets to promote electron transfer across the CdS/MoS2 interfaces as well as hydrogen reduction, leading to an efficient H2 evolution reaction.

Three families of ZnTe magic-sized nanoclusters (MSNCs) were obtained exclusively using polytellurides as a tellurium precursor in a one-pot reaction by simply varying the reaction temperature and time only. Different ZnTe MSNCs exhibit different self-assembling or aggregation behavior, owing to their different structure, cluster size, and dipole–dipole interactions. The smallest family of ZnTe MSNCs (F323) does not reveal a crystalline structure and as a result assembles into lamellar triangle plates. Continuous heating of as synthesized ZnTe F323 assemblies resulted in the formation of ZnTe F398 MSNCs with wurzite structure and concomitant transformation into lamellar rectangle assemblies with the organization of nanoclusters along the ⟨002⟩ direction. Further annealing of ZnTe F398 assembled lamellar rectangles leads to full organization of MSNCs in all directions and formation of larger ZnTe F444 NCs that spontaneously form ultrathin nanowires following an oriented attachment mechanism. The key step in control over the size distribution of ZnTe ultrathin nanowires is, in fact, the growth mechanism of ZnTe F398 MSNCs; namely, the step growth mechanism enables formation of more uniform nanowires compared to those obtained by continuous growth mechanism. High yield of ZnTe nanowires is achieved as a result of the wurzite structure of F398 precursor. Transient absorption (TA) measurements show that all three families possess ultrafast dynamics of photogenerated electrons, despite their different crystalline structures.

•High performance electrochemical supercapacitor electrode material.•Interlayer expanded MoS2 to achieve enhanced capacitance.•Facile hydrothermal synthesis of interlayer expanded MoS2.•MoS2 nanosheets assembled incompact nanorods.Rational structural design for electrode materials is essential for fabricating high performance supercapacitors. In this work, we demonstrated a novel way to prepare incompact MoS2 nanosheets assembled nanorods with the interlayer of MoS2 nanosheets expanded to 0.89 nm, namely layer expanded MoS2 nanorods (LE-MoS2 NRs). The material was characterized by XRD, XPS and electron microscopes. The XRD data and HRTEM images confirmed the existence of expanded interlayer of MoS2 nanosheets. N2 adsorption-desorption isotherms of LE-MoS2 NRs indicated high specific area up to 37.0 m2 g−1. It was found that the expanded interlayer spacing can benefit the ion transportation within the MoS2 interlayers. The as-prepared electrode material showed capacitance up to 231 F g−1 at 1 A g−1 charge-discharge current and cycling stability test indicated high capacitance of 177 F g−1 was retained after 1000 cycles.

•A novel and efficient hybrid composed of CoP NRs and NPCFs was constructed.•The CoP/NPCFs hybrid catalyst exhibits efficient electrocatalytic activity for HER.•The defects and catalytic active sites were enhanced after N, P codoping.•The synergetic effect between NPCFs and CoP contributes to high catalytic activity.•This study opens a door for designing novel CoP-based HER electrocatalysts.How to enhance the catalytic performance of electrocatalyst for the hydrogen evolution reaction (HER) is the main focus among many researches. In this work, an efficient hybrid composed of CoP nanorods (NRs) and N, P co-doped carbon flakes (NPCFs) which were synthesized by direct pyrolysis of the mixture of biomass macromolecule sodium alginate and ammonium hypophosphite was constructed. The as-synthesized CoP/NPCFs hybrid catalyst exhibits efficient electrocatalytic activity with a low onset overpotential (45 mV), small Tafel slope (67 mV dec−1), high exchange current density (1.37 × 10−3 mA cm−2), large electrochemical double-layer capacitance (9.25 mF cm−2) and good stability for HER in 0.5 M H2SO4 solution. The good HER electrocatalytic performance derived from the more defects and active sites in the catalyst as well as the strong synergetic effect between NPCFs and CoP NRs. This study opens a door for designing low-cost transition metal phosphide catalysts decorated heteroatom doped carbon materials for water splitting.

The development of visible-light-responsive photocatalysts is a promising challenge in the management of environmental pollution. Silver–silver halide nano-photocatalysts have received intensive attention due to their excellent photocatalytic performance in recent years, where silver nanoparticles/nanoclusters demonstrate plasmonic enhanced light absorption efficiency and have been considered as an important component in various functional photocatalytic nanocomposite materials, serving for harvesting visible light. This review provides an overall survey on the state-of-the-art silver–silver halide-based photocatalysts, fundamental understanding of their plasmonically induced photo-reactions and their major environmental applications. We first discuss the basic concepts of localized surface plasmon resonance, and outline the general mechanism of silver–silver halide-based photocatalysis. We then discuss the latest progress in the design and fabrication of silver halide based photocatalysis using various strategies. Next, we highlight some selected examples to demonstrate the new applications of silver/silver halide nano-photocatalysts. Eventually, we provide an outlook of the present challenges and some perspectives of new directions in this interesting and emerging research area.