Solar Hydrogen Production Utilizing a High-Performance p+n−Si Photocathode: Catalysis by g-C ₃ N ₄ and Stabilization via Al ₂ O ₃ Buffer Layer

In this work, we propose a cost-effective wet-chemical method to combine graphitic carbon nitride (g-C 3 N 4 ) with [Formula: see text]Si. The integration of g-C 3 N 4 onto [Formula: see text]Si led to a notable enhancement in its photoelectrochemical (PEC) properties, primarily due to the g-C 3 N 4 catalyst’s electrochemical activities. By inserting a thin Al 2 O 3 buffer layer between g-C 3 N 4 and [Formula: see text]Si, we further optimized the PEC performance and stability. The resulting g-C 3 N 4 /Al 2 O 3 /[Formula: see text]Si photocathode displayed impressive efficiency, characterized by an onset potential (V[Formula: see text]) of 0.72 V[Formula: see text], a photocurrent density of −32.1 mA/cm 2 at 0 V[Formula: see text] (J 0 ) and an energy conversion efficiency [Formula: see text] of 5.3% under 100 mA/cm 2 Xe lamp /illumination, and maintaining continuous water splitting for 36 h.