Highly efficient hydrogen evolution with silicon nanowire photocathodes: hierarchical triple-junction and a-MoSx catalysts achieving ABPE > 4.6%

Abstract

Silicon-based photocathodes hold immense potential for solar-driven hydrogen evolution but suffer from inherent limitations including severe light reflection, rapid charge recombination, and insufficient catalytic activity. This work demonstrates a sustainable tripartite strategy integrating light management, carrier separation, and catalyst engineering. TiO₂-clad silicon nanowire arrays (SiNWs/TiO₂) fabricated via metal-assisted chemical etching (MACE) and magnetron sputtering achieve low reflectance and efficient charge extraction. Electro-deposited amorphous MoS_x (a-MoS_x) synthesized at 25 °C exhibits 44% S₂²⁻ ligands and 80.6-fold higher carrier density than its crystalline counterparts, enabling optimal hydrogen adsorption kinetics (ΔG_H* = 0.03 eV). The optimized SiNWs/TiO₂/a-MoS_x achieves a record 4.6% applied bias efficiency (0.33 V_RHE) with 0.58 V onset potential, −20.3 mA cm⁻² photocurrent density, and >18 h stability, outperforming Pt-free Si-based systems. This work establishes a scalable paradigm for high-efficiency photoelectrodes through synergistic integration of nanostructuring, heterojunction engineering, and metastable catalyst design, advancing the sustainable production of solar fuels.