Examining the Potential of CuO/ZnBi2O4 Heterojunction Photocathode in the Photoelectrochemical Water-Splitting Applications

Abstract

The primary objective of this study is to synthesize and examine a highly efficient photo-catalyst endowed with robust and sustained photo-catalytic capabilities, with a particular focus on its applicability within photoelectrochemical (PEC) processes. The methodology employed involves the hydrothermal synthesis of CuO, subsequently subjected to a spin-coating process for the deposition of ZnBi₂O₄ (ZBO) across a multi-layer, followed by high-temperature annealing for structure optimization. A comprehensive suite of analyses encompassing morphological, structural, textual, optical, and PEC measurements was conducted on the synthesized samples. Experimental findings underscore the notable enhancement in photo-catalytic performance achieved through the formation of heterojunction, particularly conductive to facilitating the PEC hydrogen evolution reaction (HER) process when juxtaposed with the individual constituents (CuO and ZBO). Among these samples, CuO/ZBO-10 exhibited commendable photo-stability and demonstrated remarkable visible-light-induced photo-catalytic efficiency in driving the PEC HER process. The integration of ZBO coatings notably augments the PEC performance of CuO, with the CuO/ZBO-10 photocathode attaining a photo-current density of up to -1.35 mA.cm⁻² at 0 V vs. RHE, under standard test conditions. Importantly, the CuO/ZBO-10 photocathode exhibits superior retention of optical activity, with 63.11% maintained after 3600 s of irradiation, significantly surpassing the performance of bare CuO (10.98%). A detailed examination of the experimental data elucidates that the observed enhancements in photo-current density and stability can be attributed to the facilitated electrochemical charge transfer at the electrode/electrolyte interface and the concomitant mitigation of photo-corrosion rates.