Defect-engineered ultrathin g-C3N4 nanosheets anchored with nickel clusters via dual-functional modification for synergistically enhanced photocatalytic hydrogen evolution

Abstract

The rational design of co-catalysts with broad spectral response and efficient charge separation remains a critical challenge in photocatalysis. In this study, we propose a dual-functional modification strategy integrating defect engineering and transition metal cluster anchoring to construct a high-performance ACNNS/Ni composite. Ultrathin g-C₃N₄ nanosheets (CNNS) were first etched with NH₄F to create surface defects, serving as anchoring sites for uniformly dispersing Ni clusters. These defects not only enhanced intrinsic photocatalytic activity but also enabled stable Ni cluster loading, forming a Schottky barrier at the Ni/g-C₃N₄ interface to facilitate electron transfer and suppress recombination. The optimized ACNNS/Ni exhibited a narrowed bandgap (2.37 eV vs. 2.65 eV for pristine CNNS), extended visible-light absorption to 477 nm, and achieved a remarkable hydrogen evolution rate of 2.85 mmol/(g h) under simulated sunlight—5.82 times higher than pure CNNS. Notably, the defect-rich structure and Ni clusters synergistically improved charge separation efficiency, as evidenced by a 12-fold increase in photocurrent density and reduced charge transfer resistance. Furthermore, cyclic tests confirmed robust stability, retaining 82% activity after five cycles. This work highlights the significance of “defect engineering-metal cluster anchoring” in tailoring heterojunction systems, offering a universal pathway for developing transition metal-modified 2D photocatalysts with broad spectral utilization and high quantum efficiency.