•WP2 nanosheets on graphite paper (NSs/GP) with porous architecture was prepared.•Pulsed laser deposition was used to prepare the seed layer for WP2 NSs/GP.•WP2 NSs/GP exhibits enhanced HER catalytic activities.Herein, porous WP2 nanosheet arrays integrated on graphite paper (P-WP2 NSs/GP) as 3D flexible cathode for electrocatalytic hydrogen evolution reaction (HER) are prepared by in situ phosphidation via vacuum encapsulation assisted by pulsed laser deposition technique. Compared to the electrode without pre-deposition process, the enhanced catalytic activities are attributed to the increased effective catalyst loading and the reinforced charge transport kinetics. The results make the present P-WP2 NSs/GP as a promising cathode for energy conversion and paves a new way for designing and fabricating efficient electrodes toward HER.Download high-res image (180KB)Download full-size image

•Self-supported 3D porous CoP3 on carbon cloth are prepared.•CoP3 nanospheres exhibit superior catalytic activity for overall water splitting.•The mechanism of enhanced electrocatalytic activity for CoP3 was investigated.Developing high-efficiency, low-cost and non-precious metal electrocatalysts for future renewable energy conversion systems is highly desired. In this work, self-supported three-dimensional porous CoP3 nanospheres on carbon cloth (CoP3 NSs/CC) are fabricated via topotactic phosphidation of Co3O4 NSs/CC. The synthesized CoP3 NSs/CC, as a novel non-precious-metal electrocatalyst with large specific surface area and high porosity, exhibits efficient bifunctional electrocatalytic performance in alkaline medium, with Tafel slopes of 66 mV dec−1 and 72 mV dec−1, and a current density of 10 mA cm−2 at overpotentials of −121 and 291 mV for HER and OER, respectively, which are remarkably superior to those of transition metal phosphides (TMPs). In addition, it just needs a cell voltage of 1.54 V to acquire a current density of 10 mA cm−2 for overall water splitting. The results of our work may shed light on the direction toward highly efficient bifunctional TMPs electrocatalysts with high phosphorous component.Download high-res image (301KB)Download full-size image

Making full use of solar energy and achieving high charge separation efficiency are critical factors for the photocatalysis technique. In this work, we report core–shell structured fibrous phosphorus (f-P) coated P-doped Cr2O3 (Cr2O3:P@f-P) hybrid composites with a strong optical absorption in the full region of 200–2600 nm. The Cr2O3:P@f-P hybrid composites exhibit a record photocatalytic efficiency under UV, visible and near-infrared light irradiation, demonstrating as promising photocatalysts for the full utilization of solar energy. Systematical investigations combining experimental and theoretical work show that P doping modifies the electronic band structures and creates defective levels in the forbidden gap of Cr2O3 which extends the optical absorption to the visible and near-infrared regions. Highly crystalline fibrous phosphorus in situ grown on the Cr2O3 particles constructs a core–shell hybrid structure which guarantees intimate interfacial contact between f-P and Cr2O3:P and facilitates the separation of photogenerated electron–hole pairs. This study develops a promising system based on earth abundant element P to utilize the overall spectrum of sunlight for photochemical applications.

Developing low-cost and highly-efficient non-precious metal bifunctional electrocatalysts towards the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an attractively alternative strategy to solve the environmental pollution problems and energy demands. In this study, metal–organic framework (MOF) derived porous cobalt poly-phosphide (CoP3) concave polyhedrons are prepared and explored as superior bifunctional electrocatalysts for the HER and OER. The prepared MOF derived CoP3 concave polyhedrons show excellent electrocatalytic activity and stability towards the HER and OER in both acidic and alkaline media, with the Tafel slopes of 53 mV dec−1 and 76 mV dec−1 and a current density of 10 mA cm−2 at the overpotentials of −78 and 343 mV for the HER and OER, respectively, which are remarkably superior to those of the transition metal phosphides (TMPs) and comparable to those of the commercial precious metal catalysts. In addition, they also offer efficient catalytic activities and durabilities under neutral and basic conditions for the HER. The results of our study may shed light on the direction towards highly efficient bifunctional TMP electrocatalysts with high phosphorous component.

•Polymorphic WP2 were prepared by phase-controlled phosphating reaction.•Polymorphic WP2 exhibits high HER catalytic activity in wide pH media.•The reasons for the superior performance of polymorphic WP2 are explored.The design and development of high-efficiency and non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean and renewable energy system has excited significant research interests over the recent years. In this communication, the polymorphic tungsten diphosphide (p-WP2) nanoparticles with mixed monoclinic (α-) and orthorhombic (β-) phases are synthesized by phase-controlled phosphidation route via vacuum capsulation and explored as a novel efficient electrocatalyst towards HER. The p-WP2 catalyst delivers superior performance with excellent stability under both acidic and alkaline conditions over its single phases of α-WP2 and β-WP2. This finding demonstrates that a highly efficient hybrid electrocatalyst can be achieved via precise composition controlling and may open up exciting opportunities for their practical applications toward energy conversion.Download high-res image (280KB)Download full-size image

We report on a novel MoS2/S-doped g-C3N4 heterojunction film with high visible-light photoelectrochemical (PEC) performance. The heterojunction films are prepared by CVD growth of S-doped g-C3N4 film on indium–tin oxide (ITO) glass substrates, with subsequent deposition of a low bandgap, 1.69 eV, visible-light response MoS2 layer by hydrothermal synthesis. Adding thiourea into melamine as the coprecursor not only facilitates the growth of g-C3N4 films but also introduces S dopants into the films, which significantly improves the PEC performance. The fabricated MoS2/S-doped g-C3N4 heterojunction film offers an enhanced anodic photocurrent of as high as ∼1.2 × 10–4 A/cm2 at an applied potential of +0.5 V vs Ag/AgCl under the visible light irradiation. The enhanced PEC performance of MoS2/S-doped g-C3N4 film is believed due to the improved light absorption and the efficient charge separation of the photogenerated charge at the MoS2/S-doped g-C3N4 interface. The convenient preparation of carbon nitride based heterojunction films in this work can be widely used to design new heterojunction photoelectrodes or photocatalysts with high performance for H2 evolution.Keywords: film; MoS2; p-n heterojunction; photoelectrochemical; S-doped g-C3N4

•A novel MoP2 electrocatalyst is proposed for hydrogen evolution reaction.•MoP2 nanoparticles demonstrate high activity towards HER compared with MoP.•MoP2 nanoparticles exhibit excellent stability for practical application.•The enhanced electrocatalytic mechanism was comprehensively studied.Transition metal phosphides (TMPs) are burgeoning as novel electrocatalysts to replace noble metals for electrochemical production of hydrogen. In this work, we propose a novel and cost-effective catalyst, molybdenum diphosphide (MoP2) three-dimensional porous structural nanoparticles with superior activity towards the hydrogen evolution reaction (HER). MoP2 nanoparticles catalyst exhibits an onset overpotential of −38 mV, a Tafel slope of 52 mV dev−1 and an exchange current density of 0.038 mA cm−2. Furthermore, the catalyst only needs low overpotentials of −121 and −193 mV to produce operationally relevant cathodic current densities of −10 and −100 mA cm−2, respectively, and its catalytic activity is maintained for at least 24 h. Comparative study with MoP nanoparticles as electrocatalyst for HER clearly indicates that MoP2 with high phosphor component can potentially improve the electrocatalytic activities. Density functional theory (DFT) calculation shows that the higher electrocatalytic activity of MoP2 over MoP can be attributed to a longer HP bond length, lower hydrogen adsorption energy, lower HER energy barrier and luxuriant surface active sites. This work may expand the TMPs family to poly-phosphides as active and cost-effective hydrogen electrode for the large-scale hydrogen production.

The development of high-efficiency and non-noble metal hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. In this work, monoclinic tungsten diphosphide (α-WP2) and orthorhombic tungsten diphosphide (β-WP2) particles were synthesized through a phase-controlled solid-state phosphating reaction route via vacuum encapsulation technique, and were evaluated as HER electrocatalysts. Structural characterizations indicate single phase highly crystalline α- and β-WP2 particles with sub-micron sizes were successfully prepared. Both catalysts deliver remarkable catalytic activity for HER with good stability in acidic media. However, α-WP2 particles exhibit better catalytic activity than β-WP2 with a lower overpotential for achieving cathodic current density of 10 mA cm−2 and a smaller Tafel slope. Combining experimental measurements and theoretical calculations based on density functional theory (DFT), we conclude that the higher catalytic activity of α-WP2 over β-WP2 can be attributed to the less transfer of electron density from W to P due to a longer W-P bond length, the higher electron conductivity and better charge transfer, the lower kinetic energy barrier of H atom adsorption on catalysts surface for HER and longer H-P bond length for effective desorption of H atom to form H-H bond. Our findings may help the development of transition metal poly-phosphide with precise phase controlling technique for applications in hydrogen production.

•The α-Fe2O3/g-C3N4 heterostructures were successfully synthesized.•The heterostructures demonstrate a excellent gas sensing performance.•The heterostructure accelerates electron transfer and improves the gas sensing response.The α-Fe2O3/g-C3N4 nanocomposites were synthesized by a hydrothermal and pyrolysis method. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques, which indicates porous α-Fe2O3 nanotubes wrapped by lamellar g-C3N4 structure. Due to the formation of heterojunctions, the α-Fe2O3/g-C3N4 nanocomposites demonstrate a better gas sensing performance than the pure α-Fe2O3 and g-C3N4. The α-Fe2O3/g-C3N4 heterojunctional composites with g-C3N4 60% weight present a maximum gas-sensing response of 7.76 toward 100 ppm ethanol at the optimum operating temperature of 340 °C, which is about 3 and 7 times higher than that of the pure α-Fe2O3 porous nanotubes and pure g-C3N4 nanopowders, respectively. Furthermore, the α-Fe2O3/g-C3N4 nanocomposites exhibit excellent selectivity to ethanol gas, faster response and recovery time than those of the pure α-Fe2O3 porous nanotubes and pure g-C3N4 powders. The possible reason for the enhanced sensing performance obtained from the α-Fe2O3/g-C3N4 nanocomposites is attributed to the porous α-Fe2O3 nanotubes wrapped by lamellar g-C3N4 nanostructures and the formation of heterojunction. The findings reported in this study will be useful to the design and construction of metal oxide nanostructures based heterojunctional structures with enhanced gas sensing performance.

•BiOClxBr1−x homogeneous solid solutions with hierarchical nanostructures were synthesized.•The band gaps were largely modified and the light utilization improved.•The BiOCl0.5Br0.5 exhibits superior photocatalytic performances for the oxidation of NO.•Modified band-gap adapts the balance between adequate redox potentials and light absorption.•The mechanism behind the enhanced photocatalytic performance are discussed.Bismuth oxyhalides (BiOX, X = Cl, Br, I) as effective photocatalysts have attracted a wide attention for its outstanding performance on air purification with solar energy. In this work, a series of band-gap engineered BiOClxBr1−x homogeneous solid solution materials were explored as efficient visible-light induced photocatalysts. The BiOClxBr1−x solid solution photocatalysts with 3D hierarchical nanostructures have been successfully synthesized through a facile temple free hydrothermal method. The prepared BiOClxBr1−x possess a single tetragonal crystal structure without any secondary phases in spite of x varying from 0 to 1 indicating a homogeneous solid-solution characteristic. However, the band gaps of BiOClxBr1−x solid solutions are modulated from 3.30 to 2.75 eV by decreasing x from 1 to 0, which extends the light absorption from 375 nm to 450 nm. The obtained BiOCl0.5Br0.5 sample displays enhanced photocatalytic activity for the oxidation of NO, with a good stability under visible light. The existence of hydroxyl radicals and super oxygen radicals confirm its photocatalytic activities. The highly enhanced visible light photocatalytic activity of BiOCl0.5Br0.5 can be ascribed to the large specific surface area, hierarchical structures and the modified band structures. Furthermore, the modified band-gap adapts the balance between adequate redox potentials and effective visible light absorption. The present work provides novel insights into the design and synthesis of 3D hierarchical nanostructures with band-gap engineering to explore novel photocatalysts.

The production of clean and renewable H2 by photocatalytic water splitting has attracted much attention due to the increasing energy crisis. In this work, semimetallic MoP2 nanoparticles are discovered as a new photocatalyst to efficiently degenerate methyl orange and produce H2 from water under visible light irradiation. MoP2 nanoparticles were prepared using a solid-state reaction route via a vacuum encapsulation technique followed by acid washing. Both first-principle band-structure calculations and experimental measurements reveal typical semimetallic characteristics for MoP2. The obtained MoP2 nanoparticles display superior photocatalytic performances for the degradation of methyl orange with a good stability and the reduction of water assisted by sacrificial elemental Pt under visible light. The detection of hydroxyl radicals in the solution in the presence of MoP2 with fluorescence spectroscopy confirmed its photodegradable activities. The present study points out a new direction for developing semimetallic photocatalysts for H2 production through water splitting.

Doping with impurities as well as introducing oxygen vacancies has been recognized as an important means to enhance photocatalytic activity of TiO2 under visible-light irradiation. Here we report that simple ethanol impregnation followed with mild heat treatment (150–400 °C) can color TiO2 nanoparticles and enhance visible-light photocatalytic activity of the material. The coloration and photocatalytic activity for β-naphthol and rhodamine B (RhB) degradation were observed to be dependent on heat-treatment temperature, and the highest activity as well as the most coloration was obtained at temperatures around 200 to 250 °C. Comprehensive analyses based on X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) investigations as well as first-principle density functional calculation suggest that the simple ethanol impregnation treatment leads to the generation of oxygen vacancy on TiO2 surface which should be responsible for the coloration and enhanced photocatalytic activity.Keywords: density functional calculation; ethanol impregnation; oxygen vacancy; TiO2; visible-light photocatalyst;

We demonstrate the tuning of the electrical transport properties of MoS2 nanosheets by intercalating phosphorus (P). The P-doped MoS2 nanosheets were synthesized by a facile hydrothermal method. The structures and electrical properties of P-doped MoS2 nanosheets were systematically investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, transmission electron microscopy, Raman spectral analysis, adsorption spectra analysis, and Hall measurements. The results indicate that the stacking of the (002) plane in multilayered MoS2 nanosheets is inhibited and the interlayer spacing is enlarged with the introduction of P atoms. Both experimental results and theoretical calculations indicate that P atoms are much easier to intercalate into the interlayers of MoS2, compared with substitution of Mo and S, which significantly affects the vibrational modes of Raman spectra. Furthermore, because of the extra electrons introduced by intercalating P atoms, the conductivity of MoS2 could be gradually modulated from p-type to n-type by increasing the content of intercalated P. This demonstration of tuning the electrical transport properties of MoS2 could help in the design of electrical and optoelectronic devices based on layered metal dichalcogenides.

Ferromagnetism has been induced in nanostructured TiO2/Al powders prepared by ball milling at room temperature. This study presents the investigation of the origin of the magnetism in a TiO2/Al system with a combination of experiments and density functional theory (DFT) simulations. Our results demonstrate that adsorption of Al on surfaces of TiO2 nanostructures yields spontaneous magnetization. Our DFT simulations show that spin-polarized charge-transfer occurs from an adsorbed Al atom to O 2p state in surface and subsurface for some unique configurations. X-ray absorption near edge structure (XANES) spectra of the magnetic nanostructured TiO2/Al provide the necessary experimental evidence of the charge transfer and confirm the origin of ferromagnetic behavior. On the basis of the experiments and DFT simulations, we believe the room temperature ferromagnetism in nanostructured TiO2/Al originates from charge-transfer from Al to O atoms. Our results illustrate a complex interplay between the atomic level interfacial structure and the resulting ferromagnetic ordering in metal-coated semiconductor oxide nanostructures.

Self-supported porous cobalt poly-phosphide nanoneedle arrays on carbon fiber paper (CoP3 NAs/CFP) are fabricated via topotactic phosphidation of the Co(OH)F/CFP precursor. The prepared CoP3 NAs/CFP, as a 3D structured electrocatalyst with a large specific surface area and high porosity, exhibits superior bifunctional electrocatalytic activity and durability for both the HER and OER.

The production of clean and renewable H2 by photocatalytic water splitting has attracted much attention due to the increasing energy crisis. In this work, semimetallic MoP2 nanoparticles are discovered as a new photocatalyst to efficiently degenerate methyl orange and produce H2 from water under visible light irradiation. MoP2 nanoparticles were prepared using a solid-state reaction route via a vacuum encapsulation technique followed by acid washing. Both first-principle band-structure calculations and experimental measurements reveal typical semimetallic characteristics for MoP2. The obtained MoP2 nanoparticles display superior photocatalytic performances for the degradation of methyl orange with a good stability and the reduction of water assisted by sacrificial elemental Pt under visible light. The detection of hydroxyl radicals in the solution in the presence of MoP2 with fluorescence spectroscopy confirmed its photodegradable activities. The present study points out a new direction for developing semimetallic photocatalysts for H2 production through water splitting.

Developing low-cost and highly-efficient non-precious metal bifunctional electrocatalysts towards the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an attractively alternative strategy to solve the environmental pollution problems and energy demands. In this study, metal–organic framework (MOF) derived porous cobalt poly-phosphide (CoP3) concave polyhedrons are prepared and explored as superior bifunctional electrocatalysts for the HER and OER. The prepared MOF derived CoP3 concave polyhedrons show excellent electrocatalytic activity and stability towards the HER and OER in both acidic and alkaline media, with the Tafel slopes of 53 mV dec−1 and 76 mV dec−1 and a current density of 10 mA cm−2 at the overpotentials of −78 and 343 mV for the HER and OER, respectively, which are remarkably superior to those of the transition metal phosphides (TMPs) and comparable to those of the commercial precious metal catalysts. In addition, they also offer efficient catalytic activities and durabilities under neutral and basic conditions for the HER. The results of our study may shed light on the direction towards highly efficient bifunctional TMP electrocatalysts with high phosphorous component.