Solar Hydrogen Production Utilizing a High-Performance p + n - Si Photocathode: Catalysis by g -C₃N₄v and Stabilization via Al₂O₃ Buffer Layer

In this work, we propose a cost-effective wet-chemical method to combine graphitic carbon nitride (g-C₃N₄) with p+n-Si. The integration of g-C₃N₄ onto p+n-Si led to a notable enhancement in its photoelectrochemical (PEC) properties, primarily due to the g-C₃N₄ catalyst's electrochemical activities. By inserting a thin Al₂O₃ buffer layer between g-C₃N₄ and p+n-Si, we further optimized the PEC performance and stability. The resulting g-C₃N₄/Al₂O₃/p+n-Si photocathode displayed impressive efficiency, characterized by an onset potential (Von) of 0.72 VRHE, a photocurrent density of -32.1 mA/cm² at 0 VRHE (J₀) and an energy conversion efficiency (η) of 5.3% under 100 mA/cm² Xe lamp /illumination, and maintaining continuous water splitting for 36 h.