Preparation Of ZnO/Cu₂O Nanotube Array Heterostructure And Study On Its Photoelectric Properties

In recent years,solar photoelectrochemical(PEC)technology based on semiconductor for production of hydrogen from water has gained wide attention and recognition in solving the energy shortage and environmental crisis.Among many semiconductor materials,ZnO is considered as one of the most promising photoelectrode materials and has a wide range of applications.However,due to the wide band gap width,the use of visible light by ZnO has been greatly restricted,which has affected the widespread application of ZnO materials in the decomposition of water by PEC to a certain extent.In this paper,cubic and spherical Cu2O crystals were deposited on ZnO nanotube arrays by a simple electrodeposition method.By adjusting the deposition potential,two heterostructures of ZnO/Cu2O nanotube arrays loaded by Cu2O crystals with different morphologies were constructed.The performance of ZnO/Cu2O nanotube arrays are significantly affected by the morphology and size of Cu2O crystals.The specific research content of this paper is divided into the following parts.(1)Electrodeposition and chemical etching methods were used to prepare ZnO nanotube arrays.Zn(NO3)2·6H2O was selected as the Zn source,and PEG-400 and C2H8N2 were used as auxiliary materials to prepare ZnO nanorod arrays with a wurtzite structure.KOH solution was used as the etching agent to obtain ZnO nanotube arrays The result shows that the ZnO nanotube arrays have higher light absorption capacity and PEC performance due to the larger surface area.(2)The ZnO/Cu2O nanotube arrays loaded with cubic Cu2O crystals(hereinafter referred to as ZnO/Cu2Ocub)were prepared.ZnO nanotube arrays,Cu(NO3)2·3H2O and C3H6O3 were used as the substrate,the copper source and the stabilizer,respectively,and the pH value of the electrolyte was adjusted by NaOH.The ZnO/Cu2Ocub nanotube arrays were obtained by using the constant potential method at the deposition potential of-0.5 V.The results show that the Cu2O crystals in this heterostructure have a regular cubic morphology,and the size and number of Cu2O crystals increase with the increase of the deposition time.The visible light absorption of the ZnO/Cu2Ocub heterostructure is greatly enhanced compared with that of pure ZnO.The photocurrent generated by the ZnO/Cu2Ocub heterostructure under visible light irradiation is also significantly higher than that by pure ZnO,and the size and number of Cu2O crystals have a great influence on the PEC performance of the ZnO/Cu2Ocub heterostructure.Finally,the mechanism of the transfer and separation of the photogenerated charge in ZnO/Cu2Ocub nanotube arrays is proposed.(3)The ZnO/Cu2O nanotube arrays loaded with spherical Cu2O crystals(hereinafter referred to as ZnO/Cu2Osph)were prepared.The ZnO nanotube arrays,Cu(NO3)2.3H2O and C3H6O3 were used as the substrate,the copper source and the stabilizer,respectively,and the pH value of the electrolyte was adjusted by NaOH.The ZnO/Cu2Osph nanotube arrays were obtained by using the constant potential method at the deposition potential of-0.7 V.The Cu2O crystals in this heterostructure have a spherical morphology,and the size and number of Cu2O crystals increase with the increase of the deposition time.The visible light absorption of ZnO/Cu2Osph heterostructure is significantly improved compared to pure ZnO nanotube arrays,and the photocurrent generated by ZnO/Cu2Osph nanotube arrays under visible light irradiation is higher than that of ZnO nanotube arrays.In addition,the size and number of Cu2O particles greatly affect the PEC performance of the heterostructure.Finally,the mechanism of the transfer and separation of the photogenerated charge in ZnO/Cu2Osph nanotube arrays is proposed.