Regulation For Separation Charcterisitics Of Photogenerated Carriers On The Surface Of WO₃-Based Photoanode

Photoelectrochemical water splitting by semiconductor can directly convert solar energy into H₂ material,which is one of the ideal strategies to solve the energy crisis.Currently,in the process for photoelectrochemical water splitting,the separation and surface reactions of carriers on the surface of the semiconductor are limited by both thermodynamics and kinetics,becoming the main reason for limiting photoelectrochemical water splitting.Among many semiconductors,WO₃ has a moderate band gap of².7 eV,and has good mobility,which is a proming photoanode.However,photo-generated carriers have the property of being easily recombined and difficult to inject water molecules on the surface of WO₃ photoanode,which is the main factor limiting its water oxidation performance.Therefore,this paper takes WO₃photoanode as the target material to study and regulate the separation charcteristics of photo-generated carrier on the its surface.The main research contents and conclusions of the paper are as follows:?1?The high surface state of nanostructured WO₃ photoanode is the major limited factor for its phtoelectrochemical water oxidation performance.This paper report that amorphous TiO₂??-TiO₂?be used as passivator to modify the surface states of WO₃ nanoflakes film for improving its PEC water oxidation performance.The photocurrent on?-TiO₂/WO₃ film photoanode is improved by 2 times that reached 1.4 mA/cm² at same condition.The density functional theory calculations indicate after coupling with?-TiO₂,the surface energy of WO₃was reduced from 1.17 J/m² to 0.3 J/m².Therefore,the enhanced PEC water oxidation performance on?-TiO2/WO₃ film can be attributed to that?-TiO2 passivates the surface states of WO₃ nanoflakes film.?2?Improvements to the water oxidation activity for WO₃ photoanodes due to oxygen vacancies have in general been ascribed to charge transfer and separation effects from conventional thermodynamics.However,detailed insights into the water oxidation kinetics for these types of photoanodes are still lacking.This paper investigated the influence of oxygen vacancies on the kinetic mechanism of WO₃ photoanodes for solar water oxidation.The experimental results show that the introduction of oxygen vacancies mainly improves the carrier injection efficiency of WO₃ photoanode?from 36.9%to 69.5%?,making the WO₃photoanode with oxygen vacancies is more inclined to follow the four-hole pathway.Theoretical calculations revealed that the H₂O adsorption and subsequent dehydrogenation on the WO₃ photoanode are more energetically favorable when oxygen vacancies are present,which improves the rate of water oxidation related steps.?3?Photoanodes with different specific exposed crystal faces exhibit significant water-oxygen differences.Herein,the separation and transport of photo-generated carriers are regulated by loading a single?002?facet of WO₃ on the surface of WO₃ with multi-facets.The experimental results show that after loading WO₃ with a single?002?facet,the carrier separation efficiency increased from 39.2%to 63.7%;the injection efficiency increased from 35.6%to 60.3%,which is mainly due to the following two points:1)The multi-facets of WO₃ and the single?002?facet of WO₃ have energy band differences,which is thermodynamically beneficial for the separation of photo-generated carriers.2)WO₃?002?film has good hydrophilicity,which could accelerate the peripheral electrolyte to penetrate on the interface between the electrode and the electrolyte,showing better water oxidation kinetics...