Synthesis Of Bismuth Vanadate Nanomaterials And Study On The Photoelectric Water Splitting

The production of hydrogen from photoelectrochemical?PEC?water splitting,as a promising method to capture solar energy into chemical fuels,has attracted wide scientific and technological interest.To construct a practical PEC device,efficient photoanode materials with adequate light absorption,effective charge separation,and high surface reactivity are required.Among various semiconductors,bismuth vanadate?BiVO₄?has emerged as a promising n-type photoanode material for PEC water splitting owning to its intrinsic advantages,including small band gap energy?ca.2.4 eV?,favorable band-edge positions,and low onset potential.However,most reported photocurrent densities of BiVO₄ are far below its theoretical expectation(7.5mA cm^-2 under AM 1.5G),suffering from a poor charge separation and transport,severe surface recombination,and sluggish water oxidation kinetics.To address these issues,based on the previous works,this paper mainly focuses on the preparation and application of photoanode materials based on BiVO₄.The following innovative researches were carried out.?1?A facile and simple spin-coating method has been employed for the fabrication of a MIL-53?Fe?-2%Mo:BiVO₄ composite photocatalytic material.The iron-based MIL-53?Fe?metal-organic framework could serve as an efficient hole-transfer co-catalyst to significantly improve the PEC performance of 2%Mo:BiVO₄ photoanodes.More specifically,the MIL-53?Fe?-2%Mo:BiVO₄photoanode shows a photocurrent of 2.2 mA cm^-2 at 1.23 V_RHE in a 0.2 M Na₂SO₄electrolyte under AM 1.5G simulated sunlight(100 mW cm^-2).Moreover,The H₂generation capability is nearly 7 and 2 times higher than that of pure and FeOOH-modified Mo:BiVO₄,respectively.This is because MIL-53?Fe?can greatly increase the charge-carrier density and facilitate more efficient electron-hole separation.This work provides a novel insight into using MOFs as co-catalysts in PEC water oxidation via reasonable designs,which may be applied for constructing more advanced MOF-based catalysts for solar photoelectric conversion.?2?A simple solution impregnation way for growing the ultrathin and crystalline?-FeOOH cocatalyst with abundant oxygen vacancies on a nanoporous BiVO₄photoanode has been used.The resulting FeOOH/BiVO₄ photoanodes show an outstanding PEC performance for water oxidation,and a photocurrent of 4.3 mA cm^-2at 1.23 V_RHE was obtained in Na₂SO₄ solution under AM 1.5G(100 mW cm^-2)illumination,approximately 2-fold higher than that of the amorphous FeOOH nanofilms fabricated by electrodepositions.Moreover,with rationally modulating the oxygen vacancies in highly crystalline FeOOH nanolayer by in situ oxidation and reduction treatments,significantly different PEC performances have been achieved,further confirming the crucial functions of oxygen vacancies in the FeOOH cocatalyst for the significantly improved PEC activity.The new findings will pave the way toward low-cost,efficient,and stable OER cocatalysts while simultaneously producing defects for sustainable solar energy conversion.