Ag/ZnO Catalysts with Different ZnO Nanostructures for Non-enzymatic Detection of Urea

Abstract

Silver coated ZnO nanorods and nanoflakes with different crystallographic orientations were synthesized by a combination of sputter deposition and solution growth process. Catalytic properties of morphology-dependent Ag/ZnO nanostructures were then investigated for urea sensors without enzyme. Ag/ZnO nanorods on carbon electrodes exhibit a higher catalytic activity and an improved efficiency than Ag/ZnO nanoflakes on carbon electrodes. Ag/ZnO nanorod catalysts with more electrochemically surface area (169 cm2 mg−1) on carbon electrode facilitate urea electrooxidation due to easier electron transfer, which further promotes the urea electrolysis. The Ag/ZnO nanorod catalysts also show a significant reduction in the onset voltage (0.410 V vs. Ag/AgCl) and an increase in the current density (12.0 mA cm−2 mg−1) at 0.55 V vs Ag/AgCl. The results on urea electrooxidation show that Ag/ZnO nanostructures can be a potential catalyst for non-enzymatic biosensors and fuel cells.