Construction Of Novel BiVO₄-based Photoanode And Its Photoelectric Oxygen Precipitation Performance

In the 21st century,fossil energy is increasingly depleted,and there is an urgent need to develop a new type of clean energy to meet the daily production and living needs of human beings.Hydrogen energy is considered being the energy source that best meets the current“double carbon”development goals due to its unique properties.Among the many current methods of hydrogen production,the solution of producing hydrogen by photoelectrochemistry（PEC）water splitting has attracted attention in its non-polluting and low energy consumption.BiVO₄has become the preferred photoanode material due to its suitable band gap（about 2.4 e V）,non-toxic and cheap raw materials,and high photoelectric conversion efficiency.However,the inherent defects of BiVO₄,such as severe electron-hole recombination and weak surface water oxidation kinetics,hinder its practical application.To address these issues,we have concentrated on the effect of a dual modification scheme of heteroatom doping and further loading of a water oxidation reaction co-catalyst on the PEC water oxidation performance of BiVO₄photoanode,and this work contains the following three parts:（1）A new type of Ni Fe₂O₄-Nd-BiVO₄photoanode was prepared by a one-step electroplating method.In the process of synthesizing BiVO₄photoanode by electrodeposition,the rare earth element neodymium（Nd）was directly doped into its bulk phase,and the Ni Fe₂O₄co-catalyst was loaded on the surface of Nd-doped BiVO₄by the spin coating-calcination method.The newly prepared photoanode showed a higher photocurrent density and a significant negative shift in the onset potential.Detailed characterization proves that Nd doping can induce lattice distortion of BiVO₄to improve its light absorption performance.In addition,the doped Nd can act as an electron donor,increasing the carrier density and reducing the hole-electron recombination.As a co-catalyst,Ni Fe₂O₄can accelerate hole transfer,reduce electron-hole recombination and increase surface water oxidation kinetics.（2）A new LMNCO-Nd-BiVO₄photoanode was prepared by anchoring Li-rich manganese（LMNCO）co-catalyst on Nd-doped BiVO₄.The newly prepared photoanode showed a higher photocurrent density and a significant negative shift in the onset potential.Detailed characterizations prove that Nd doped can significantly increase carrier concentration and effectively reduce electron-hole recombination.The Ni and Co in the LMNCO co-catalyst play the role of hole extraction and water oxidation reaction active sites,respectively.Under the synergistic effect of the two modification methods,the photo-generated holes can quickly migrate from the bulk phase of BiVO₄to the semiconductor-electrolyte interface and oxidize with the water molecules adsorbed on the surface of the BiVO₄photoanode,thereby reducing the accumulation of holes in the bulk phase and greatly improving the PEC water oxidation performance and stability of the BiVO₄photoanode.（3）The Ni₂P₂O₇-Nd-BiVO₄photoanode were prepared by depositing Ni₂P₂O₇co-catalyst on the Nd-doped BiVO₄surface by light-driven electrophoresis.The newly prepared photoanode showed a higher photocurrent density and a significant negative shift in the onset potential.Detailed characterizations prove that the Nd doped can significantly increase the carrier concentration,increase the energy band bending degree,reduce the degree of electron-hole recombination,and increase the conductivity.The Ni₂P₂O₇co-catalyst has a triple effect.On the one hand,it can be used as a photosensitizer to improve the light absorption performance of BiVO₄photoanode.On the other hand,it can be used as a hole extraction layer to accelerate the extraction of photo-generated holes and improve the stability of BiVO₄photoanode.Finally,the deposition of Ni₂P₂O₇co-catalyst increases the electrochemically active area and kinetically accelerates the surface water oxidation reaction.