Preparation Of CuBi₂O₄-Based Photocathode For Efficient Hydrogen Production From Water Splitting

Hydrogen（H₂）has been considered one of the most promising energy source for solving the excessive carbon footprint problem due to its high energy density and zero-pollution end product（H₂O）.photoelectrochemical（PEC）water splitting can use solar energy（one of the most abundant renewable energies）to produce hydrogen with water as raw material,which has become a research hotspot in recent years.The most important component of PEC water splitting system includes photocathode and photoanode.Great progress has been made in the development of photoanodes,but there are still many issues,which limit the development of PEC technology.Metal oxide materials have attracted wide attention,with the advantages of abundant reserves in the earth,low cost and simple synthesis process.However,the PEC hydrogen evolution performance of metal oxide photocathode is still far from practical application due to the presence of crystal defects（point defects,pinholes and grain boundaries）,low carrier mobility and severe recombination of photogenerated electron-hole pairs.To solve the problems,in this thesis,CuBi₂O₄ was used as a model semiconductor.A straightforward sol-gel method with a unique ligand-induced growth strategy was employed to reduce crystal defects,which promotes photogenerated carrier transport and reduces photogenerated electron-hole pair recombination.Furthermore,CuBi₂O₄ and CuO were composited to form CuBi₂O₄/CuO photocathodes with Type-Ⅱheterojunction,which facilitates the separation of photogenerated carriers and reduces the charge transfer resistance.The detailed content in this thesis is as follow.1、Preparation of CuBi₂O₄ photocathode by unique ligand-induced growth strategy for efficient PEC hydrogen evolution reactionIn this work,a straightforward sol-gel method with a unique ligand-induced growth strategy was employed to prepare the dense and homogeneous copper bismuthate photocathodes for PEC hydrogen evolution reaction.CuBi₂O₄ thin films（2-CuBi₂O₄）with high crystallinity and coverage,large grain size and low oxygen vacancy defect were obtained by using ethylene glycol methyl ether as ligand.2-CuBi₂O₄ photocathode possesses the advantages of high light absorption capacity and carrier mobility,and reduced photoelectron-hole pair recombination.Consequently,under simulated sunlight irradiation,the 2-CuBi₂O₄ photocathode achieved an enhanced photocurrent density of-0.98 m A cm^-2 at 0.4V versus the reversible hydrogen electrode（RHE）and a promising applied bias photon-to-current efficiency（ABPE）of 0.414%.This surface modification of ligand growth strategy is favorable for the design of advanced photoelectrodes for PEC water splitting.2、Preparation of CuBi₂O₄/CuO heterojunction photocathode for efficient PEC hydrogen evolution reactionHerein,CuBi₂O₄/CuO heterojunction photocathodes were prepared by sol-gel treatment and repeated double potential pulse chronograph method.A series of CuBi₂O₄/CuO heterojunction photocathodes with different material ratios were obtained by adjusting the total deposition time.CuBi₂O₄/CuO photocathode displays more efficient incident light utilization,less charge transfer resistance,and the delayed recombination of photogenerated electron-hole pair than control samples.Under simulated sunlight irradiation,the CuBi₂O₄/CuO photocathode achieved an enhanced photocurrent density of-1.28 m A cm^-2 at 0.4V versus RHE and a promising applied bias photon-to-current efficiency（ABPE）of 0.515%.This study will shed light on designing photocatalysts with excellent performance and stability.