| The main threat to human development comes from environmental pollution and energy crises,and it is an urgent need to find green and sustainable alternative energy sources.Photoelectrochemistry（PEC） has been recognized as one of the effective ways to solve environmental pollution and energy crisis.Comparatively speaking,a large number of n-type semiconductors have been explored as photoanodes in photoelectrochemical cells,while only a few photocathodes based on metal oxides have been investigated.The ternary copper-based oxide CuBi2O4 is a promising material that satisfies the theoretically feasible solar hydrogen production requirements due to its low cost,rich earth content,non-toxicity,and adjustable light absorption range.However,there are still some unsolved problems such as poor charge carrier transport ability,photo-induced corrosion,and inacceptable stability.In view of the above-mentioned shortcomings of CuBi2O4 photoelectrode,this dissertation proposes to use co-modification of doping and cocatalyst,and the combination of heterojunction and surface passivation to effectively improve its photoelectrochemical performance.The main research contents include the following two aspects:We designed a convenient film transfer technique and a simple adsorption process to prepare Ag and N-doped graphene quantum dot co-modified CuBi2O4（NGQDs/Ag-CBO） submicron rod photocathode.PEC activities of NGQDs/Ag-CBO submicron rod photoelectrode was systematically compared with those of original CBO,Ag-CBO,NGQDs/CBO submicron rod photoelectrode,and NGQDs/Ag-CBO microsphere photoelectrode.The photocurrent density achieved on NGQDs/Ag-CBO SMRs photocathode at 0.3 V vs.RHE（71μA/cm2）was 8.8,2.3,1.8,and 5.9-times larger than those obtained on CBO submicron rods（8μA/cm2）,Ag-CBO submicron rods（30μA/cm2）,the NGQDs/CBO submicron rod（39μA/cm2）and the NGQDs/Ag-CBO microsphere photoelectrode（12μA/cm2）,respectively.Based on experimental results,the effects of Ag+ ion doping and NGQDs loading and their synergistic effect are revealed.The enhanced photoelectrochemical activity of NGQDs/Ag-CBO nanorods can be attributed to the collective action of one-dimensional structure,Ag+ ion doping and NGQDs loading.The present research provides a new method for synthesizing and designing highly efficient photoelectrode materials.We designed a simple synthesis strategy for the first time to prepare a uniform and dense CuBi2O4-CuO high-quality heterojunction film by vacuum thermal evaporation of Cu and Bi metals and subsequent annealing treatment on the FTO substrate.The order,the ratio of coating elements,coating thickness,annealing time and temperature had obvious effects on crystallinity,morphology,structure and optoelectronic properties.Subsequently,the photoelectrochemical activity was improved by introducing an ultrathin Ga2O3 film to construct p-n junction,passivating the surface state and promoting carrier separation.Finally,the photocurrent was further enhanced by modifying the photoelectrode with Pt co-catalysts.This work provides a new idea for solving the limitations of CuBi2O4 photocathode during the process of solar water decomposition. |
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