Structure Design And Photoelectrochemical Properties Of Cadmium Sulfide Photoanode

The energy crisis and environmental pollution have a profound effect on today’s human society,both in terms of life and production.Hydrogen energy production and utilization is a viable solution to relieve these two pressures.The photoelectric synergetic catalytic system for water splitting hydrogen production is composed of two core half reactions,namely the oxygen production reaction on the photoanode and the hydrogen production reaction on the opposite electrode.The development of high-performance photoanode materials is essential in order to enhance the performance of the photocatalytic water decomposition reaction.Cadmium sulfide（CdS）with a suitable band gap structure for hydrogen and oxygen production has excellent properties such as high absorbance,high electron mobility,and a wide optical response range,making it a potential photoanode material.However,the carrier recombination caused by the defect state on the surface of CdS and the self-decomposition under long illumination seriously hinder its efficiency and stability.The concept of passivation layers,derived from metal anticorrosion,is used to transform the metal surface into a state that is not easily oxidized,thus delaying the corrosion rate of the metal.Passivation treatments of semiconductors prone to photoetching can effectively inhibit their self-decomposition and improve the stability of photoelectric electrodes,making it a research hotspot in the field of photocatalysis.In this thesis,the effects of dopamine polymer（PDA）and inorganic alumina layer（Al₂O₃）on alleviating the photocorrosion of CdS and improving the carrier separation efficiency were investigated,focusing on the design and preparation of passivation layers for CdS photoanodes.Additionally,the carrier separation and transport mechanism of the modified composite photoanode was analyzed.（1）Taking CdS nanorods array grown on FTO conductive glass by hydrothermal process as the research object,dopamine（DA）was polymerized and deposited on the array by solution oxidation method to obtain a CdS/PDA composite photoanode.By utilizing the natural adhesion of PDA,the oxygen-producing co-catalyst Fe OOH was loaded onto the PDA.The results showed that the photocurrent density of the CdS/PDA composite photoanode was higher and more stable than that of the pure CdS photoanode.The successful combination of the PDA passivation layer effectively improved the photocatalytic activity and stability of the CdS.Furthermore,the photocatalytic performance of the composite photoanode was further improved after the successful coupling of Fe OOH.（2）On the basis of the research on the formation of the CdS/PDA heterojunction,an Al₂O₃film was introduced to passivate the CdS photoanode.It was found that the high density negative charge in the Al₂O₃layer could consume photogenerated holes and promote the separation of photogenerated carriers.The double passivation of the Al₂O₃thin film and PDA on the pure CdS effectively inhibited electron-hole recombination.The experimental data demonstrated that the photocurrent density of the CdS/PDA/Al₂O₃composite photoanode was much higher than that of the pure CdS photoanode.The composite structure optimized the interfacial charge transfer during the photocatalytic process,thus improving the efficiency of electrode/electrolyte interfacial charge injection.