Hierarchical NiCo2O4@NiWO4 core–shell nanowire arrays supported on nickel foam have been synthesized via a facile hydrothermal route coupled with a post-thermal treatment. The hydrothermally synthesized NiCo2O4 nanowire arrays serve as the scaffold for anchoring the NiWO4 nanosheets. When evaluated as binder-free electrodes for supercapacitors, the optimized NiCo2O4@NiWO4 hybrid electrode demonstrates remarkable electrochemical performance with a high specific capacitance of 1384 F g−1 at a current density of 1 A g−1 and superior cycling stability (87.6% retention over 6000 cycles at a current density of 5 A g−1). In addition, an asymmetric supercapacitor (ASC) based on the optimized NiCo2O4@NiWO4 electrode and activated carbon is assembled with 6 M KOH as the electrolyte. The as-fabricated ASC device can achieve a maximum high energy density of 41.5 W h kg−1 at a power density of 760 W kg−1. The excellent supercapacitive performance could be ascribed to the unique core–shell architecture and the synergistic effect from the NiCo2O4 nanowires and the ultrathin NiWO4 nanosheets.

•An efficient strategy to steer bulk and surface charge separation by creating an external electric field (EEF) as a driving force was proposed.•The external electric field (EEF) is derived by molecules interface functionalization with strong positive Si charges.•The universality is confirmed using many other photocatalysts and opens up a potential application to construct high-performance photoelectrodes for solar water splitting.Realizing efficient charge separation and transfer is a key challenge for solar energy conversion. Here, we proposed the creation of an external electric field (EEF) by molecules interface engineering with silane grafting to form strong positive electricity on surface in semiconductor photocatalyst, driving charge separation and transfer in both bulk and surface. Forced by the EEF, WO3 nanoplates anchored silane molecules (WO3-SiH2NH2) for efficient photoelectrochemical (PEC) water oxidation shows 44.8% photocurrent enhancement. Interestingly, the photocurrent onset on WO3-SiH2NH2 exhibited a 0.3 V negative shift from 0.5 to 0.2 VRHE compared with pure WO3 caused by the change of band edge position. The strategy of creating EEF is proven effective using other semiconductors and opens up a potential application to construct numerous high performance photoelectrodes for water splitting.The creation of an external electric field (EEF) by molecules interface engineering with silane grafting to form strong positive electricity on surface of photocatalysts was proposed, driving efficient charge separation. The universality is confirmed by many photocatalysts and opens up a potential application to construct high-performance photoelectrodes for water splitting.Download high-res image (251KB)Download full-size image

Carbon quantum dot sensitized Pt@Bi2WO6/FTO electrodes (simplified as CQDs-Pt@Bi2WO6/FTO) were successfully prepared by loading platinum particles onto Bi2WO6 nanoplates via a photo-deposition method and sensitized carbon quantum dots (CQDs) via a dip-coating method. The photoelectro-catalytic properties of the Pt@Bi2WO6/FTO and CQDs-Pt@Bi2WO6/FTO electrodes for methanol oxidation were investigated. The results indicated that the CQDs-Pt@Bi2WO6/FTO electrode shows higher photoelectro-catalytic activity and better stability than that of the Pt@Bi2WO6/FTO electrode. The higher photoelectro-catalytic performance for methanol oxidation was attributed due to the special synergetic effects between the photocatalytic and electrocatalytic process under solar light irradiation. More importantly, the introduction of CQDs broaden the photoresponse range of the Bi2WO6 material and improves the mobility of the photocarriers. Meanwhile, the doped CQDs act as preferential adsorption sites for the intermediate carbonaceous species during methanol oxidation. This not only alleviates CO poisoning towards the Pt particles, but also improves the efficiency of methanol oxidation by constructing a new type of CQDs-Pt electrocatalyst. The composite material, which combines the dual function of photocatalysis and electrocatalysis will be a promising candidate for new photoelectro-catalytic fuel cells.

AbstractThree-dimensional (3D) porous Bi2WO6/reduced graphene oxide hydrogels (BWO/rGO HGs) have been prepared via a facile one-pot hydrothermal process for supercapacitor applications. Compared with the pristine Bi2WO6 electrode, the 3D porous BWO/rGO HGs exhibit much higher capacitive performances with a specific capacitance of 268.7 F g−1 at a current density of 0.75 A g−1 and good cycling stability with 81% capacitance retention after 1000 cycles at 3 A g−1. The remarkable electrochemical properties could be attributed to unique architecture of 3D porous rGO HGs supported Bi2WO6, which provided an excellent electrical conductivity substrate and more channels for ions diffusion. The results indicate that a new synthesis route of 3D porous structure hydrogel loaded binary metal oxide have potential applications in energy storage device.

Vertically grown WO3 nanoplates (WO3NP) were successfully fabricated by a one-step hydrothermal process using citric acid as a structure directing agent. An innovative etching method was developed to obtain increased surface voids, active crystal facets and surface groups simultaneously, which led to a remarkably improved photocurrent density of ∼1.2 mA cm−2 at 1.23 V vs. RHE, compared to 0.97 mA cm−2 of pristine WO3. Incident photon to current efficiency (IPCE) measurements also displayed a substantive increase of photoresponse in the intrinsic absorption range. Interestingly, a lower onset potential can be obtained after etching which is caused by the change of conduction and valence band positions. Moreover, the photoelectrocatalytic activity of WO3 for degrading methylene blue (MB) was also evaluated. This effective design could provide a promising method to enhance the efficiency of photoelectrochemical performance based on WO3 photoanodes.

A novel hierarchically structured WO3–CNT@TiO2NS composite was prepared by the combination of solvothermal and liquid-phase chemistry deposition techniques. The obtained composite has a highly rough and porous structure with WO3 nanoparticles distributed uniformly on the surface. The photocatalytic performance was tested by photocatalytic degradation of methylene blue. It is indicated that the WO3–CNT@TiO2NS composite shows more remarkable improvement of the photocatalytic performance than that of the CNT@TiO2NS. In particular, the presence of 15 wt% WO3 enables reaching the highest photocatalytic activity, which is 4 times that of CNT@TiO2NS. The enhanced photocatalytic properties are mainly attributed to the more efficient photogenerated carrier separation, enhanced light absorption as well as the higher adsorption ability. It is suggested that WO3 deposition is a promising way to enhance the photocatalytic activity of a TiO2-based photocatalyst.

The mesoporous material ordered mesoporous carbon/tungsten carbide (OMC/WC) was prepared and used as electrocatalyst for methanol electro-oxidation. WC embedded OMCs was synthesized through carbothermal reactions with a blow of argon and hydrogen by employing ammonium metatungstate as a precursor. In this method, because OMC acted both as the support and the carbon sources, not only the surface area of materials is enlarged, but also the generation of deposit carbon which covers the active sites can be effectively avoided. The characterization, which carried out by X-ray diffraction, Transmission electron microscopy and N2 adsorption–desorption measurement showed a homogeneous distribution of WC throughout the surface of the mesoporous carbon and the surface area of OMC/WCs was up to 344 m2/g. Electro-catalytic properties and mechanism of methanol oxidation on the OMC/WCs electrode has been investigated using cyclic voltammetry and in situ FTIR technique. The results showed that there was only one characteristic methanol oxidation peak during the whole potential scan on the OMC/WCs electrode surface, it also showed an improved CO tolerance of the WC surface. It proved that tungsten carbide had good electro-catalytic property close to that of the Pt-based materials for methanol oxidation and provided a new idea for developing electrode materials in the future.

Mesoporous material with functional group (Pt4+-NH2-MCM-41) was prepared by grafting aminopropyl group and adsorbing platinum ions on the surface of the commercial molecular sieve (MCM-41). The characterization carried out by X-ray photoelectron spectroscopy, X-ray diffraction, and N2 adsorption–desorption measurement pointed out that Pt was adsorbed on the NH2-MCM-41 surface as the oxidation state (Pt4+) and the surface area of Pt4+-NH2-MCM-41 was up to 564 m2/g. Transmission electron microscopy and elemental mapping indicated a homogeneous distribution of Pt4+ throughout all surface of the mesoporous materials. Electro-catalytic properties of methanol oxidation on the Pt4+-NH2-MCM-41 electrode were investigated with electrochemical methods. The results showed that the Pt4+-NH2-MCM-41 electrode exhibited catalytic activity in the methanol electro-oxidation with the apparent activation energy being 49.29 kJ/mol, and the control step of methanol electro-oxidation was the mass transfer process. It is first proved that platinum ions had good electro-catalytic property for methanol oxidation and provided a new idea for developing electrode materials in future.Graphical abstractHighlights► It was first confirmed that the Pt4+ exhibited a good electro-catalytic property for methanol oxidation. ► The Pt4+ perfectly distributed on a mesoporous molecular sieve matrix synthesis by a facile method. ► The good performance of catalyst resistance to poisoning because of a homogeneous distribution of Pt4+ and large specific surface area.

The polyporous carbon supported tungsten carbide (polyporous C@WC1−x) composite was prepared using hexagonal silica MCM-41 as the hard template by raw material solution impregnation, mechanical milling and simultaneous reduction and carbonization by temperature programming in mixture gas (CH4/H2). The structure and morphology of polyporous C@WC1−x composite were studied via X-ray diffraction, transmission electron microscopy and so on. The electrocatalytic property was tested for the electroreduction of p-nitrophenol (PNP) in neutral media. Results revealed that the composite is consisted of polyporous carbon and nanocrystalline WC1−x, possessing good electrocatalytic activity in the reaction of PNP reduction.

Sandwiched film of MnO2 nanosheet (MONS) and multi-walled carbon nanotube (MWCNT) was assembled by using the layer-by-layer method, based on electrostatic interaction of positively-charged poly (diallyl dimethyl ammonium chloride) and negatively-charged MONS and MWCNT. Ultraviolet–visible spectroscopy is used to probe the dynamic growth of multilayer film, exhibiting progressive enhancement of optical absorption due to the assembly of MONS and MWCNT. Thus, the assembled sandwiched film was characterized using scanning electron microscopy and X-ray photoelectron spectra. The multilayer film electrode presents excellent electrochemical capacitance properties, which were also highly dependent upon the deposition sequence and the order of structural components in sandwiched film.

The development of the process of fabricating well-aligned nanostructures materials is one of the interesting subjects in current material science. This paper describes a new method to fabricate high-density, vertically-aligned nanorods of metal and metal compound by magnetron sputtering on aluminum lattice membrane (ALM). The ALM was formed by chemical etching of the hexagonal arrays of pore layer from the anodic aluminum oxide membrane, resulting in unnumbered hemisphere nanopits with uniform protuberant nanodots on the surface of aluminum. The ALM was employed as a substrate to fabricate well-aligned Ni, Cu, WC nanorod films by magnetron sputtering. Scanning electron microscopy images showed that the sputtered atoms have been absorbed preferentially onto the protuberant nanodots of ALM in the process of magnetron sputtering, and have begun to nucleate and grow into nanorods. The diameter of the nanorods depends on the diameter of hemisphere on the surface of the substrate, while the thickness of thin films can be controlled by deposition time.

Thiol functionalized mesoporous silica (TFMS) with ordered hexagonal pore structure was fabricated by one-step synthesis pathway. The selective adsorption for precious metals was investigated using single component and binary adsorption solutions. The TFMS displayed strong affinity for gold or platinum in specific conditions with a large adsorption capacity, and showed a high selectivity in the binary solutions within 30 min. Furthermore, gold and platinum could be totally recovered by elution with 5 M HCl and 0.7 M thiourea–2 M HCl, respectively.Graphical abstractDownload full-size imageHighlights► Thiol functionalized adsorbent was fabricated by a one-step synthesis pathway. ► The adsorbent was used for removal and recovery of gold and platinum from solutions. ► The adsorbent which adsorbed gold or platinum can be recovered completely.

Hierarchical NiCo2O4@NiWO4 core–shell nanowire arrays supported on nickel foam have been synthesized via a facile hydrothermal route coupled with a post-thermal treatment. The hydrothermally synthesized NiCo2O4 nanowire arrays serve as the scaffold for anchoring the NiWO4 nanosheets. When evaluated as binder-free electrodes for supercapacitors, the optimized NiCo2O4@NiWO4 hybrid electrode demonstrates remarkable electrochemical performance with a high specific capacitance of 1384 F g−1 at a current density of 1 A g−1 and superior cycling stability (87.6% retention over 6000 cycles at a current density of 5 A g−1). In addition, an asymmetric supercapacitor (ASC) based on the optimized NiCo2O4@NiWO4 electrode and activated carbon is assembled with 6 M KOH as the electrolyte. The as-fabricated ASC device can achieve a maximum high energy density of 41.5 W h kg−1 at a power density of 760 W kg−1. The excellent supercapacitive performance could be ascribed to the unique core–shell architecture and the synergistic effect from the NiCo2O4 nanowires and the ultrathin NiWO4 nanosheets.

A novel hierarchically structured WO3–CNT@TiO2NS composite was prepared by the combination of solvothermal and liquid-phase chemistry deposition techniques. The obtained composite has a highly rough and porous structure with WO3 nanoparticles distributed uniformly on the surface. The photocatalytic performance was tested by photocatalytic degradation of methylene blue. It is indicated that the WO3–CNT@TiO2NS composite shows more remarkable improvement of the photocatalytic performance than that of the CNT@TiO2NS. In particular, the presence of 15 wt% WO3 enables reaching the highest photocatalytic activity, which is 4 times that of CNT@TiO2NS. The enhanced photocatalytic properties are mainly attributed to the more efficient photogenerated carrier separation, enhanced light absorption as well as the higher adsorption ability. It is suggested that WO3 deposition is a promising way to enhance the photocatalytic activity of a TiO2-based photocatalyst.