Preparation And Photoelectrochemical Performance Of FeVO₄ And GC₃N₄ Semiconductor Materials

With the development of the global economy and the rapid growth of population,energy crisis and environmental pollution have become two major problems in modern society.Photoelectrochemical water splitting into gaseous hydrogen using semiconductor materials is an effective way to address increasing energy demand and related environmental problems.In this paper,pristine FeVO₄ and g-C₃N₄ semiconductor materials were prepared by high temperature hydrothermal method and thermal polycondensation method.Compared with pristine Fe VO₄ and g-C₃N₄ samples,we have prepared semiconductor materials with remarkable electrochemical performance after direct thermal oxidation etching treatment.The crystal structure,chemical composition and optical properties were investigated by means of XRD,UV-Vis-DRS and SEM et al.The photoelectrochemical performances were tested by Linear sweep voltammetry?LSV?,AC impedance spectroscopy?EIS?and Mott-Schottky techniques et al.The main conclusions are as follows:?1?After thermal oxidation etching treatment,the structure of pristine FeVO₄ material,which nanostructure was nanorods and bundled up,were turned into nanoparticles and nanorods alternatively distributed structure and the FeVO₄ nanoparticles attached on the surface of rod-shaped Fe VO₄.Due to the scattering of FeVO₄ nanoparticles,the optical properties of FeVO₄ samples were improved,and the photo absorption edge was detected red shift.This structure can increase the penetration of electrolyte solution into the inner of FeVO₄ electrode and then reinforce the separation of photoexcited electron-hole pairs.The flat band potential(E_FB)was occurred with positive shift,which reduced the accumulation of electrons at the solution/electrode interface.The pseudo-first-order rate constants for the charge transfer at the illuminated solution/electrode interface were significantly increased for the etched FeVO₄electrode.?2?The ultrathin and nanoporous g-C₃N₄ nanosheets with excellent performance were prepared through thermal oxidation etching process with different duration?1-7 h?for the pristine g-C₃N₄ materials.Compared with pristine g-C₃N₄ samples,the improved crystalline of etched g-C₃N₄ can be ascribed to the decreased structural defects?-NH₂,-NH?,which were originated from more complete condensation during thermal oxidation etching process.And the etched g-C₃N₄ materials have detected red shifts in the photo absorption edge.The physical chemistry properties and photoelectrochemical performance of g-C₃N₄ were gradually enhanced with the increasing of thermal oxidation etching time.As the time of thermal oxidation etching was 5 h,the g-C₃N₄ achieved its best physical chemistry properties and photoelectrochemical performance,and the photocurrent and separating efficiency of photoexcited electron-hole pairs for g-C₃N₄ electrode were significantly increased.However,when the time of thermal oxidation etching was 6h,the physical chemistry properties and photoelectrochemical performance started to decrease due to the over etching destroyed the nanostructure of g-C₃N₄ samples.