Synthesis of Sn doped ZnO/CuI based p-n heterojunction photoanode for Photoelectrochemical water splitting

Abstract

Abstract

 In the forthcoming era, our next generation would witness a shift from non-renewable resource dependent society towards a society that relies on renewable resources due to ecological footprint, rising prices of fossil fuels, unsecured energy and anticipated depletion of age old fossil reserves. The principal goal of 21^st century is to secure the eco-friendly ambience and sustainable fuels as the ecological balance is hampered with each passing day. Harvesting energy from the sun is contemplated to be one of the notable choices to meet the ever increasing energy demands of the current progressive society due to its abundance, cost-effectiveness and eco-amiable nature. Due to worldwide abatement of energy resources, it is a current need for the researchers to make use of sustainable resources including clean energy H₂. Photoelectrochemical splitting of water into H₂ and O₂ turned out to be a constructive strategy to overcome the prevailing energy crunch. Over the decades, numerous semiconductors based on metal-oxides have been widely investigated as photoanodes for photoelectrochemical applications. ZnO has been considered as a significant material due to its excellent optoelectronic properties but the main drawback of this semiconductor is its limited absorbance in the visible range of the solar spectrum. In order to activate its properties in the visible region different strategies were opted such as doping or coupling low band gap semiconductors with large band gap semiconductors. In this work, ZnO is doped with different concentrations of Sn and coupled with CuI to construct a p-n heterostructure. Compared to bare ZnO, 5%Sn:ZnO/CuI manifested better absorbance in visible region, enhanced photocurrent density (0.56 mA/cm²), more negative flat band potential, high charge carrier density and least semi-circular arc radius in Nyquist plot.