Ag-modified ZnO nanorods and its dual application in visible light-driven photoelectrochemical water oxidation and photocatalytic dye degradation: A correlation between optical and electrochemical properties

Abstract

In this work, Ag-ZnO composite was prepared at different weight percentages using a modified hydrothermal method for application to the photoelectrochemical (PEC) water oxidation and photocatalytic dye degradation. The resulting samples were studied using structural, surface, optical and photoelectrochemical (PEC) characterization methods. The surface plasmon resonance (SPR) of the optimal catalyst played an essential role in the synergistic improvement of the optical response and the photoinduced charge carrier separation process. The optimal Ag modified ZnO (3 wt% of Ag) showed superior photocatalytic and water oxidation performance. The inclusion of Ag has also played a vital role in the defect concentration and the Schottky junction at the metal–metal oxide interface. As a result, the PEC behavior of the optimal samples showed drastic improvements in terms of water oxidation current response under visible light illumination. Consequently, the photocatalytic performance of the samples also exhibits a linear relationship with the PEC water oxidation performance. The PEC and photocatalytic performance of the optimal sample showed almost five and seven times superior performance than the pristine ZnO in terms of photocurrent value and rate constant value, respectively. This can be attributed to the existence of the Schottky junction leading to the minimum charge transfer resistance and better charge transport across the interface. The superiority of the optimal sample is explained in terms of the physicochemical properties and electrochemistry of the material. To the best of the authors’ knowledge, this is the first report on the role of optimal Ag content in ZnO for its dual application. The combined study offering complete information, the work provides guidelines for noble metal-modified catalyst research moving forward.