SiO<sub><i>x</i></sub> Interfacial Engineering\nof UV/Ozone Oxidation for an Efficient Water-Reduction Metal–Insulator–Semiconductor\nSilicon Photocathode

A metal–insulator–semiconductor (MIS) structure\nis\nan attractive interfacial structure for efficient photoelectrochemical\n(PEC) water-splitting reactions. However, developing a cost-effective\nand highly active photoelectrode for the PEC water-splitting reaction\nis still a major challenge. In this study, we use an easy-to-operate\nand economical UV/ozone (UV/O<sub>3</sub>) oxidation process to prepare\nultrathin SiO<sub><i>x</i></sub> oxide as an insulating\nlayer, which is integrated with the bilayer non-precious-metal collector\nAl/Ni serving as the catalyst and the p-Si semiconductor to obtain\na cost-effective and efficient MIS structure photocathode. The outcomes\ndemonstrate that the ultrathin SiO<sub><i>x</i></sub> insulation\nlayer significantly improves the PEC hydrogen evolution reaction (HER),\nthrough comparing the photovoltage and photocurrent density of the\nMIS system. The inner metal Al in the bilayer collector Al/Ni regulates\nthe degree of band bending at the semiconductor–metal interface.\nAdditionally, the presence of the ultrathin Al<sub>2</sub>O<sub>3</sub> insulation layer effectively reduces Fermi-level pinning, which\npromotes the efficient transfer of photoelectrons to electrolytes.\nThese were confirmed through photoelectric performance testing of\nthe MIS system. The generation of a photocurrent of 15 mA cm<sup>–2</sup> at a potential level of 0 V (vs reversible hydrogen electrode) has\nbeen obtained by optimizing the thickness of the SiO<sub><i>x</i></sub> and bilayer non-precious-metal collector. This study presents\nan economical and efficient strategy for enhancing PEC-HER performance\nin silicon-based photocathodes using an MIS structure.