High-efficiency photocatalytic hydrogen production from monolayer Bi2S4: A first-principles study

Monolayer Bi 2 S 4 , is a promising novel two-dimensional photocatalyst predicted through density functional theory (DFT) to be effective for solar-driven hydrogen production. This study highlights Bi 2 S 4 as a mechanically robust semiconductor with a more accurate HSE-calculated bandgap of 2.16 eV, making it well-suited for absorbing visible light. Its optical performance is characterized by a high absorption coefficient (∼10 5 cm −1 ) and low reflectivity, which enables efficient utilization of photon. Notably, Bi 2 S 4 exhibits pH-modulated dual functionality: under ambient conditions, its band edges align with water redox potentials, facilitating simultaneous hydrogen and oxygen evolution without the need for external co-catalysts. Our calculations predict a remarkable solar-to-hydrogen (STH) conversion efficiency of 14.36 %, approaching the theoretical maximum for materials with this bandgap. These properties position Bi 2 S 4 as a sustainable and independent photocatalyst for clean energy applications, bridging the gap between solar efficiency and scalable hydrogen production.