Preparation And Research On Catalytic Activity And Stability Of CuO Electrodes

The conversion of solar energy into clean and renewable energy is one of the promising pathways to solve environmental pollution and energy crisis.Photoelectrochemical?PEC?water splitting is a technology that can directly convert solar energy into hydrogen energy.As a p-type semiconductor material with narrow band gap,cupric oxide?CuO?is considered as an ideal photocathode material because of its low cost,simple preparation,abundant reserves,and high theoretical photocurrent value.However,the low carrier mobility and poor photocorrosion stability of CuO photoelectrodes in aqueous solutions have severely limited its practical applications in photoelectrochemical?PEC?water splitting.In this paper,the CuO photoelectrodes are firstly prpared on ITO conductive substrate by electrochemical deposition and annealing treatment,and the photocatalytic activity and stability of CuO photoelectrodes in the application of PEC water splitting are studied.To solve this issue,the noble-metal cocatalyst Pt and noble-metal-free compound cocatalyst MoS₂ are used to modify the CuO photoelectrode,respectively.The high-performance CuO/Pt and CuO/MoS₂composite photoelectrodes are successfully prepared,and the reasons for the improved photocatalytic activity and photocorrosion stability of CuO/Pt and CuO/MoS₂ composite photoelectrodes in the application of PEC for water splitting are investigated.The results show that the photocorrosion of CuO photoelectrodes during the PEC water splitting is mainly because the photogenerated electrons in the CuO photoelectrodes would reduce the Cu²⁺to Cu⁺,which reduces the catalytic activity of the CuO photoelectrode.The photocurrent density of the modified CuO/Pt and CuO/MoS₂ photoelectrodes are-0.57 and-1.64 mA/cm² at-0.55 V vs.Ag/AgCl,and their stability is 70%and 85%,respectively,which are significantly higher than that of the bare CuO.This is because cocatalyst Pt and MoS₂ can capture the photogenerated electrons of the CuO photoelectrode,and then transfer to the electrolyte solution to reduce water,which reduces the accumulation of photogenerated electrons in CuO.More importantly,MoS₂ can also form a p-n heterojunction with CuO.The built-in electric field between CuO and MoS₂ can promote the separation and transfer of photogenerated carriers,thereby improving the PEC activity and photocorrosion stability of the CuO photoelectrode.This work reveals the photocorrosion mechanism of the CuO photoelectrode,and proposes some control strategies to improve the photocatalytic activity and stability of the CuO photoelectrode,which provides a new idea for the practical application of PEC water splitting.