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

Advanced Powder Technology. 2022. Vol. 33. No. 2. Article 103434.

Das Abinash, Deka T., Kumar P. M., Bhagavathiachari M., Nair R.

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.

Keywords: Photocatalysis, Water oxidation, Zinc oxide, Surface plasmon resonance, Schottky junction