Preparation Of BiVO₄-based Composite Photoanodes And Study On Photoelectrocatalysis Property

Photoelectrocatalysis（PEC）technology with sunlight as energy input can directly drive the water decomposition reaction under the applied potential to produce H₂,relieving energy pressure.Compared with photocatalysis（PC）system,the separation and transfer of photogenerated charge carriers in PEC system can be greatly promoted because of applied electric field,thus immensely improving the efficiency of light energy conversion.Bi VO₄is one of the best materials to prepare photoanode due to its suitable conduction band（CB）and valence band（VB）,relatively wide light absorption range,low cost and non-toxicity.But it is limited by the inefficient separation of electron-hole pairs.Therefore,two kinds of Bi VO₄-based photoanodes were prepared in this paper.Firstly,O₂was produced by accelerating the four-electron process of PEC water oxidation.Secondly,adjust the electrolyte to accelerate the two-electron process of PEC water oxidation to produce H₂O₂.Further coupling with Fenton-like reaction in-situ degradation of methylene blue.Firstly,Ni Co P/Ti O₂/Bi VO₄composite photoanode was synthesized by potentiostatic electrodeposition to support Ti O₂protective layer on Bi VO₄photoanode and then using CV curve to electrodeposit Ni Co P co-catalyst.Under the conditions of simulation sunlight irradiation(100 m W cm^-2)and1.23 V vs.RHE,it shows 5.24 m A cm^-2high light current density,which is3.64 times higher than that of pure Bi VO₄(1.44 m A cm^-2).It is also better than Ni Co P/Bi VO₄(4.55 m A cm^-2).In addition,Ni Co P/Ti O₂/Bi VO₄photoanode has higher ABPE and IPCE of 1.78%and 64.2%,respectively,and the surface charge transfer efficiency of 84.0%.The relevant data showed that the Ni Co P and Ti O₂dual-layer modification enhanced the electrochemical active surface area,accelerated the separation and transfer of photogenerated carriers in Bi VO₄,and accelerated the water oxidation reaction kinetic.The stability results showed that the performance of the photoanode could be maintained for a long time by adjusting the composition of the electrolyte.Finally,Ni Co P/Ti O₂/Bi VO₄obtained ultra-long stability of nearly 65 h in the mixed electrolyte of 0.5 M K₃BO₃,0.5 M Na VO₃and 0.1 M Na₂SO₃.This work provides a feasible scheme for the preparation of high performance water decomposition photoanodes.Secondly,utilizing handful energy and chemical inputs to construct photo-assisted Fenton-like system is of significance to the treatment of pollutants in water eco-environment.Here,we constructed a Cu-C₃N₄/Mo-Bi VO₄composite photoanode capable of realizing sunlight-induced on-site H₂O₂production and activation to generate active oxygen species through a PEC-Fenton-like process to degrade pollutants efficiently.The Mo-Bi VO₄on FTO substrate achieved on-site H₂O₂production rate averaging 0.305μmol min^-1cm^-2at 2.0 V vs.RHE under AM1.5G illumination(100 m W cm^-2)in 1.5 M KHCO₃solution.The Cu-C₃N₄coated on the Mo-Bi VO₄surface synchronously activated Mo-Bi VO₄-evolved H₂O₂to produce·OH,and achieved 93.5%removal efficiency for the typical thiazine methylene blue within 30 min at neutral condition（far superior to self-contained PC（30.6%）or EC（36.8%）system）.The fabricated Cu-C₃N₄-on-Mo-Bi VO₄photoanode integrating solar-driven on-site H₂O₂generation/activation with effective pollutant degradation offers a green sustainable and manipulative pathway for actual wastewater treatment.