Alkynyl Carbon Dots in NiS-CdS: The Unique Electron Current Division Function for Enhanced Photoelectrocatalytic Hydrogen Evolution

Solar-driven photoelectrocatalytic hydrogen evolution holds great promise for sustainable hydrogen production, yet its efficiency is constrained by rapid charge recombination and limited light utilization. Herein, we successfully synthesized a coral-like NiS-CdS-CDs ternary catalyst, which integrates p–n heterojunction engineering with alkynyl-rich carbon dots (CDs). The alkynyl CDs serve dual roles as photosensitizers and electron reservoirs, significantly enhancing the light absorption and interfacial charge transfer. Coupled with the p–n heterojunction formed between NiS (p-type) and CdS (n-type), the as-prepared coral-like NiS-CdS-CDs achieve efficient carrier separation and directional electron flow. The coral-like NiS-CdS-CDs ternary catalyst manifests excellent photoelectrocatalytic hydrogen evolution performance in alkaline solution with an overpotential of 170 mV at a current density of 10 mA cm–2, a Tafel slope of 65 mV dec–1, and significant long-term durability. Density functional theory (DFT) calculations reveal that alkynyl CDs elongate the O–H bond lengths and lower the energy barrier for water activation by facilitating electron redistribution. Furthermore, the coral-like microstructure ensures high dispersion and exposes abundant active sites, addressing aggregation issues common in carbon-based cocatalysts. This work not only establishes a strategy for synergizing semiconductor heterojunctions with functionalized carbon materials but also provides mechanistic insights into electron storage-donor dynamics.