Shuxia Wang

Self-supported three-dimensional mesoporous semimetallic WP2 nanowire arrays on carbon cloth as a flexible cathode for efficient hydrogen evolution.

The design and development of high-efficiency and non-noble metal hydrogen evolution reaction (HER) electrocatalysts with optimized nanostructures for human clean and sustainable energy systems has attracted significant research interest over the past years. Herein, self-supported semimetallic tungsten diphosphide nanowire arrays on carbon cloth (WP2 NWs/CC) were topotactically fabricated by in situ phosphidation of a WO3 NWs/CC precursor. Such a binder-free flexible HER cathode with integrated three-dimensional nanostructures can not only provide a large surface area to expose abundant active sites, but also facilitate electrolyte penetration for electrons and electrolyte ions. The WP2 NWs/CC electrode exhibits superior catalytic performance, and it needs overpotentials of 109 and 160 mV with a small Tafel slope of 56 mV dec-1 to achieve current densities of 10 and 50 mA cm-2, respectively. High stability in acidic media is also observed for the catalyst for a duration of 20 hours at least. In addition, density functional theory (DFT) calculations indicate a low kinetic energy barrier for H atom adsorption on the WP2 surface which guarantees the excellent catalytic activity of the catalyst, and the influences of phosphidation temperature on the HER activity are also studied. The excellent electrocatalytic activity makes the present 3D structured WP2 NWs/CC a promising catalyst for large scale highly pure hydrogen evolution by electrochemical water splitting.

Facile preparation of semimetallic WP2 as a novel photocatalyst with high photoactivity

Searching for inexpensive and earth-abundant photocatalysts with high activities has attracted considerable research in recent years. In this work, semimetallic tungsten diphosphide (WP2) micro-particles are explored as a novel photocatalyst for the first time. The WP2 particles were synthesized through a solid-state reaction route via vacuum encapsulation technique following by water washing. The first principle calculations and electric transport measurements show a semimetallic characteristic of WP2, however a strong absorption in the UV range is observed. The prepared WP2 particles exhibit an admirable photocatalytic activity towards oxidation of methyl orange and reduction of water for H2 evolution with the assistance of co-catalyst element Pt under UV light irradiation. Hydroxyl radicals detected by fluorescence spectroscopy in the solution in the presence of WP2 under UV light irradiation confirms the photoactivity. Furthermore, the photocatalyst shows a good photostability and reusability even after three successive experiment runs. Based on the experimental measurements and theoretical calculations, a possible photocatalytic mechanism is proposed for semimetallic WP2. The present study may provide a chance for practical applications of the semimetallic material WP2 in the field of photocatalysis.

Selectively enhanced sensing performance for oxidizing gases based on ZnO nanoparticle-loaded electrospun SnO2 nanotube heterostructures

In this work, we present gas sensors based on ZnO nanoparticle-loaded electrospun SnO2 nanotube (ZnO/SnO2) n–n heterostructures (HSs) synthesized by electrospinning combined with facile thermal decomposition. The sensing properties of the pristine SnO2 nanotubes (NTs) and ZnO/SnO2 HSs were investigated toward the representative oxidizing (NO2) and reducing (H2, CO) gases. Results show that the as-prepared ZnO/SnO2 HSs exhibit selectively enhanced and diminished sensing performances for oxidizing and reducing gases, respectively. These phenomena are closely associated with the modulation of the local depletion layer on the surface of SnO2 nanoparticles (NPs) caused by charge transfer at the heterojunctions due to work function difference. A modified grain boundary-controlled sensing mechanism is proposed to describe charge transport in sensing layers based on the contact potential barriers between nanoparticles. Our study indicates that the selection of material system and their synergism are keys to the effective design of gas sensors with semiconducting metal oxide HSs.

A 3D porous WP 2 nanosheets@carbon cloth flexible electrode for efficient electrocatalytic hydrogen evolution

Self-standing porous WP2 nanosheet arrays on carbon fiber cloth (WP2 NSs/CC) were synthesized and used as a 3D flexible hydrogen evolution electrode. Because of its 3D porous nanoarray structure, the WP2 NSs/CC exhibits a remarkable catalytic activity and a high stability. By using the experimental measurements and first-principle calculations, the underlying reasons for the excellent catalytic activity were further explored. Our work makes the present WP2 NSs as a promising electrocatalyst for hydrogen evolution and provides a way to design and fabricate efficient hydrogen evolution electrodes through 3D porous nano-arrays architecture.