Porous Zn_1-xCd_xSe/ZnO Nanorod Photoanode Fabricated from ZnO Building Blocks Grown on Zn Foil for Photoelectrochemical Solar Hydrogen Production

Solar energy is the most promising, efficient, environmentally friendly energy source with the potential to meet global demand due to its non-polluting nature. Herein, a porous Zn_1-xCd_xSe/ZnO nanorod (NR) heterojunction was synthesized by hydrothermal and low-temperature solvothermal methods. First, the ZnO NR was grown on a Zinc foil, and an inorganic-organic hybrid ZnSe(en)_0.5 material was developed by the low-temperature solvothermal method. In this work, the ZnO NR acted as a base material and a building block for the growth of ZnSe(en)_0.5. Moreover, after the solvothermal process, the reduced Se^2- reacts with the ZnO NR and forms inorganic-organic hybrid ZnSe(en)_0.5. After the selenization process, the obtained material shows a red brick color due to the absorbance of excessive Se metal particles during the solvothermal process. Furthermore, in order to enhance the photoelectrochemical properties, the Cd²⁺ ion exchange method was applied at various temperatures (140, 160, and 180 °C for 3 h) to produce a precursor material to a porous Zn_1-xCd_xSe/ZnO NR nanostructure. The optimum Zn_1-xCd_xSe/ZnO NR-160 photoanode showed a high photocurrent density of 7.8 mA·cm^-2 at −0.5 V vs. Ag/AgCl with a hydrogen evolution rate of 199 μmol·cm^-2/3 h. The improved photocurrent performance was attributed to effective light absorption and prolonged recombination lifetime.