Study of the photoelectrochemical activity of ZnO: Ag/rGO photo-anodes synthesized by two-steps sol-gel method

Abstract

Abstract This work investigate the influence of Silver Plasmon and reduced graphene oxide (rGO) on the photoelectrochemical performance (PEC) of ZnO thin films synthesized by the sol-gel method. The physicochemical properties of the obtained photo-anodes were systematically studied using several characterization techniques. The X-ray diffraction analysis showed that all samples presented hexagonal Wurtzite structure with apolycrystalline nature. Raman and EDX studies confirmed the existence of both Ag and rGO in ZnO: Ag/rGO thin films. The estimated grain size obtained from (SEM) analysis decreased with Ag doping, then increased to a maximum value after rGO addition. The UV-vis transmission spectra of the as-prepared ZnO: Ag and ZnO: Ag/rGO thin films have shown a reduction in the visible range with a redshift at the absorption edges. The bandgaps were estimated to be around 3.17, 2.7, and 2.52 eV for ZnO, ZnO: Ag, and ZnO: Ag/rGO, respectively. Moreover, the electrical measurements revealed that the charge exchange processes were enhanced at the ZnO: Ag/rGO/electrolyte interface, accompanied by an increase in the (PEC) performance compared to ZnO and ZnO: Ag photo-anodes. Consequently, the photocurrent density of ZnO: Ag/rGO (0.2 mA.cm-2) was around 4 and 2.22 times higher than photo-anodes based on undoped ZnO (0.05 mA.cm-2) and ZnO: Ag (0.09 mA.cm-2), respectively. Finally, from the flat band potential and donor density, deduced from the Mott-Schottky, it was clear that all the samples were n-type semiconductors with the highest carrier density for the ZnO: Ag/rGO photo-anode.