Bridge Layer–Enabled Silicon-Based Photoanode With High Photocurrent Density for Efficient and Stable Water Splitting

Photoelectrochemical (PEC) water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen. Nevertheless, achievement of high performance is often limited by charge carrier recombination, resulting in unsatisfactory saturation current densities. To address this challenge, we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper. The optimal photoanode (TCO/n–p–Si/TCO/Ni) shows a remarkably low onset potential of 0.92 V vs. a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm⁻², which is about 92.7% of the theoretical maximum (42.7 mA·cm⁻²). In addition, the photoanode demonstrates stable operation for 60 h. Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer, enhances catalytic performance, and provides corrosion protection to the underlying substrate. Notably, the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential. These findings provide a viable pathway for fabricating high-performance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.