Effect of aspect ratio on photocatalytic performance of hexagonal ZnO nanorods

Abstract

Nanostructured zinc oxides (ZnO) are fascinating materials due to their distinct morphological properties. Current work offered controlled growth of hexagonal ZnO nanorods having range of aspect ratios (AR) synthesized through facile microwave (MW) assisted route. Structural analyses showed that the ZnO nanorods exhibit ideal growth habits along c-axis of wurtzite ZnO with various aspect ratios. The aspect ratios of ZnO vary in the range from 4.80 to 8.25, which is easily obtained through the tuning of calcination temperature alone. Based on the progression of aspect ratio and its morphological appearance, an expected growth mechanism is proposed. The effect of aspect ratio on photocatalytic activity of ZnO was studied through the decomposition of Methylene Blue (MB) and established through various physico-chemical properties. The high aspect ratio ZnO nanorods exhibit superior photocatalytic performance than the lower aspect ratio nanorods in terms of their degradation kinetics co-efficient (photonic efficiency and rate constant). It is anticipated that the superior photocatalytic performance is mainly attributed to the better charge separation and higher specific surface area with reduced equatorial growth that leads to the high aspect ratio of nanorods. It is well known that ZnO nanostructure can evolve into different morphology while tuning its aspect ratio which leads to the imprecise info about the lone effect of aspect ratio on photocatalytic performance. However, this study provides a solid fact which correlates the effect of aspect ratio on photocatalytic behaviour of ZnO by keeping its overall structure unchanged.