| Intriguing applications of transition metal oxide（TMO）nanostructures in catalysis,electronics,and photonics are driving the exploration of synthetic approaches to control and manipulate their chemical composition,morphology,and structure.However,TMOs also have some disadvantages such as wide band gap,poor conductivity,and low activity.Atomic doping,oxygen vacancy and construction of composite materials are common method for researchers to regulate the energy band structure,optimize electronic structure and improve catalytic activity of TMOs.Nevertheless,the morphology,size and macroscopic stacked state of the material often changes during the transformation.It is difficult to study the influence of the single variable on performance.Therefore,achieving the precise conversion synthesis of the target material under the condition of maintaining the material dimension,size and macroscopic stacked state still has great challenges.Solid-gas conversion synthesis chemistry is a synthesis method based on solid materials,focusing on the synthesis method of solid-gas interface reaction and diffusion law.It can realize the design and regulation of the catalyst in molecular level while maintaining the dimensionality,size and macroscopic stacked state.In this work,we take advantages of solid-gas conversion to control oxygen vacancies and build composite materials for TMOs while maintaining the shape,size and accumulation state.In addition,the relationship between material composition and catalytic performance is further studied.The main research content is covered the following parts:1.We develop a facile and universal strategy to adjust the oxygen vacancy content of TMOs by heat treatment at different oxygen partial pressure.The oxygen partial pressure of the atmosphere is changed during the heat treatment.Thus,the lattice oxygen of TMOs is overflowed in different degrees based on the solid-gas balance principle and oxygen vacancies are introduced.In addition,the electrochemical reduction treatment will further increase the content of oxygen vacancy.Therefore,we achieve a controllable adjustment of oxygen vacancy content.Our experimental results confirm the content of oxygen vacancy has a favor effect on electrocatalytic HER performance of Ni Co2O4 in alkaline solution.In addition,the density functional theory（DFT）calculations are taken to demonstrate that the increasing content of oxygen vacancy can lower the adsorption energy and activation barrier of H2O molecule on the surface of TMOs,thus improve the HER activity.2.A general low-temperature ammonia-assisted reduction strategy is reported to generate OVs in TMOs.We adopt experimental and theoretical investigations to demonstrate the mechanism of ammonia treatment.Based on this strategy,the as-prepared OV-enriched blue WO3-x porous nanorods（OBWPN）exhibit promising performance for thermal-assisted photocatalytic reduction of CO2-H2O to H2(11.9±0.5μmol g-1h-1)and CH4(45.7±1.3μmol g-1 h-1)without any external cocatalysts or sacrificial agents.This work is significant for understanding the nature of ammonia treatment and promoting the wide application of OV-enriched TMOs.3.In situ partially oxidation method is adopted to construct a close-contact WN-WO3Z-scheme heterostructure for efficient thermal-assisted photocatalytic CO2conversion with H2O.On the one hand,the Z-scheme charge transfer mode improved photo-induced carrier separation and migration efficiency.In the other hand,WN as an excellent photothermal material could efficiently converts sunlight into heat to improve catalytic rate.Thus,CO2-H2O is efficiently converted to H2,CO and CH4 by photothermally assisted photocatalytic reduction on the WN-WO3Z-scheme heterostructure.This work offers a unique perspective for transition metal nitride/oxide heterogeneous nanostructures and paves a new avenue to boost photocatalytic water splitting,CO2-to-fuel conversion and organic synthesis performance. |
