Synthesis of zinc tin oxide nanostructures and photoelectrode development for solar-driven water splitting

Abstract

Ternary oxide semiconductors (II-IV-VI oxides) have garnered significant interest recently due to superior physicochemical properties and chemical stability. Among them, zinc tin oxide stands out due to high electron mobility, electrical conductivity, attractive optical properties, wide band gap (~3.4 eV), and stability. Zinc tin oxide and its counterparts (zinc tin hydroxide, zinc tin oxynitride) have shown potential for photoelectrochemical water splitting. Considering this, the thesis work is aimed to develop zinc tin oxide and zinc tin hydroxide based photoanodes for solar driven water splitting. Primarily, zinc tin hydroxide nanoparticles are synthesized by the co-precipitation method and then recrystallized into zinc tin oxide (Zn2SnO4 and ZnSnO3) by annealing at different temperatures. The study investigates the impact of recrystallization (at varying annealing temperature) on morphological, structural, optical, and electrochemical properties. Annealing of ZnSn(OH)₆ above ~210°C forms the ZnSnO3, while annealing above ~710°C results conversion of ZnSnO3into Zn2SnO4. The photoelectrochemical characteristics of ZnSn(OH)6, ZnSnO3 and Zn2SnO4 is further investigated. The ZnSnO3 and Zn2SnO4 phases exhibited 85- and 50-fold increases in photocurrent compared to ZnSn(OH)₆ based photoanode. The effect of photoanode thickness on photoelectrochemical performance is also investigated.