Electrochemically deposited Cu ₂ O cubic particles on boron doped diamond substrate as efficient photocathode for solar hydrogen generation

Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu ₂ O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu ₂ O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu ₂ O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu ₂ O/BDD showed a much higher current density (−0.33 mA/cm ² ) and photoconversion efficiency (0.28%) compared to the unmodified Cu ₂ O/BDD electrode, which are only −0.12 mA/cm ² and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu ₂ O surface is a crucial parameter in this regard.