International Journal of Hydrogen Energy, Vol.45, No.41, 21051-21067, 2020
3D-nano-hetero-structured n/n junction, CuO/Ru-ZnO thin films, for hydrogen generation with enhanced photoelectrochemical performances
Hydrogen, derived from solar-water splitting, is a clean and renewable fuel for which per gram energy storage capacity is even higher than fossil fuels. Towards the development of a viable technology for above conversion, this report describes enhanced performance in photoelectrochemical water splitting using uniquely evolved nano-hetero-structured bilayered thin films, CuO/Ru-ZnO as photoanode. Grown over ITO (In:SnO2) glass substrates by using low-cost and easily up-scalable wet chemical methods, films were characterized for microstructure, optical behaviour and surface characteristics, using XRD and other spectral measurements viz. FESEM, AFM, TEM, UV-Visible Spectroscopy, EDX and XPS. Against monolayered pristine films of CuO and ZnO, bilayered films yielded a major gain in PEC water splitting photocurrent, on being used as working electrode in PEC cell, in conjunction with platinum counter electrode and saturated calomel reference electrode (electrolyte solution 0.1 M NaOH solution, pH 13, temperature 30 +/- 3.6 degrees C). Films with 1% Ru-incorporation yielded highest photocurrent (2.04 mA/cm(2)). Enhanced photoactivity of bilayered films was found correlated with increments in light absorption, charge carrier density and film surface area, coupled with reduced electrical resistivity. The study highlights an important role played by Ru added in ZnO overlayer, apparently existing as RuO2 nanoparticles dispersed in ZnO lattice, in hole-transfer from valence band of CuO underlayer to electrolyte, thereby imparting a significant boost on photocurrent generation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.