Effect of Au loading in the enhancement of photoelectrochemical activities of Au@ZnO nano-heteroarchitecture

Hetero-structures have delivered phenomenal photoelectrochemical performance owing to their excellent physicochemical properties. We report on the utilization of controlled Au@ZnO nano-hetero-architectures for efficient water splitting. The ZnO nanowires of average length and diameter of ~ 5-6 m and 120 nm, respectively, synthesized by the hydrothermal method were subjected to the controlled decoration of Au nanoparticles of diameter ~ 20 nm. The cubic crystalline Au nanoparticles were decorated on the hexagonal wurtzite ZnO nanowires under controlled reaction time. The 12 h reaction time has resulted in the uniform decoration of Au nanoparticles along the surface of ZnO nanowires, and a further increase in the reaction time ensued their agglomeration in the array of ZnO nanowires. The XPS analysis revealed the existence of a pure metallic Au on ZnO nanowires without altering the stoichiometry. The Au@ZnO nano-hetero-architecture with 12 h reaction time delivered maximum photocurrent density of 1.04 A/cm2, is a 52-fold increase than that of pristine ZnO nanowires. The ABPE value of 0.59 %, which is approximately five-fold higher than the pristine ZnO nanowires. This reveals that the controlled decoration of Au nanoparticles along the surface of ZnO nanowires has altered the Fermi energy position significantly and expedited the injection of the hot electron from the SP state into the conduction band of ZnO, effectively.