Abstract
Silicon, one of the most abundant and cost-effective materials on Earth, holds significant promise for applications in water splitting and photovoltaics due to its suitable bandgap energy of approximately 1.12 eV, which allows absorption of ultraviolet, visible, and infrared light. However, the high reflectivity (~25%) of flat silicon surfaces limits its conversion efficiency, making it less efficient for photoelectrochemical (PEC) processes. To address this, nanostructured silicon has emerged as a solution to enhance light absorption, reduce substrate resistance, and improve hydrogen production efficiency. In this study, we fabricated nanostructured silicon photoelectrodes using the metal-assisted chemical etching (MACE) method. The resulting black silicon (b-Si) electrodes demonstrated superior light-harvesting capabilities, leading to significantly enhanced photocurrent densities. Notably, the b-Si photoelectrodes achieved a photocurrent density of 800 μA/cm² at 0V vs RHE (reversible hydrogen electrode), compared to 200 μA/cm² for planar silicon. Furthermore, the b-Si electrodes exhibited excellent long-term stability under continuous illumination for 16 hours. These results highlight the potential of nanostructured silicon as an efficient and stable material for solar-driven PEC water splitting and related renewable energy applications.