SiO_<i>x</i> Interfacial Engineering of UV/Ozone Oxidation for an Efficient Water-Reduction Metal–Insulator–Semiconductor Silicon Photocathode

A metal–insulator–semiconductor (MIS) structure is an attractive interfacial structure for efficient photoelectrochemical (PEC) water-splitting reactions. However, developing a cost-effective and highly active photoelectrode for the PEC water-splitting reaction is still a major challenge. In this study, we use an easy-to-operate and economical UV/ozone (UV/O3) oxidation process to prepare ultrathin SiOx oxide as an insulating layer, which is integrated with the bilayer non-precious-metal collector Al/Ni serving as the catalyst and the p-Si semiconductor to obtain a cost-effective and efficient MIS structure photocathode. The outcomes demonstrate that the ultrathin SiOx insulation layer significantly improves the PEC hydrogen evolution reaction (HER), through comparing the photovoltage and photocurrent density of the MIS system. The inner metal Al in the bilayer collector Al/Ni regulates the degree of band bending at the semiconductor–metal interface. Additionally, the presence of the ultrathin Al2O3 insulation layer effectively reduces Fermi-level pinning, which promotes the efficient transfer of photoelectrons to electrolytes. These were confirmed through photoelectric performance testing of the MIS system. The generation of a photocurrent of 15 mA cm–2 at a potential level of 0 V (vs reversible hydrogen electrode) has been obtained by optimizing the thickness of the SiOx and bilayer non-precious-metal collector. This study presents an economical and efficient strategy for enhancing PEC-HER performance in silicon-based photocathodes using an MIS structure.