Unraveling Quantum Mysteries: Probing the Interplay of CdS Quantum Dots and g‑C₃N₄ Nanosheets for Enhanced Photo/Electrocatalytic Hydrogen Evolution

A series of CdS quantum dots (QDs) at low temperature were grown on the nanosheets (NSs) of g-C₃N₄ through an in situ successive ionic layer adsorption and reaction process. The visible light active band gap of ultrathin g-C₃N₄ NSs has attracted more attention due to its essential bandgap for the water splitting reaction. However, a single catalyst with a limited number of active sites does not exhibit significant photo/electrocatalytic activity for hydrogen production. In current strategies, the development of a photogenerated charge transfer-driven type-II CdS QDs/g-C₃N₄ heterostructure demonstrates an enhanced hydrogen evolution reaction with an amount of 14.8 mmol g_cat^–1 of H₂ gas and an AQY of 27.6% as a result of a decreased charge transfer resistance and a significantly increased electrochemical surface area. Additionally, the as-prepared catalyst has shown overpotentials of 182 and 382 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) reactions to reach the current density at 10 mA cm^–2, respectively. In addition, the bifunctional electrocatalyst exhibits a 4- and 6-fold higher mass current density of heterostructure material for the OER and HER reactions as compared to g-C₃N₄, with a considerable faradaic efficiency under the potentiostatic system, respectively. Moreover, the remarkable photo/electrocatalytic activity of the CdS QDs/g-C₃N₄ heterostructure was well explained through the photoluminescence quenching effect and Mott–Schottky analysis.