Efficient Hydrogen Production by γ-g-C3N4/Ag-CdS Heterojunction Photocatalyst via S-scheme Mechanism

Abstract

Photocatalytic water splitting has emerged as a promising strategy for the efficient generation of sustainable hydrogen. Among the various approaches explored, silver based cocatalysts have demonstrated significant potential in enhancing photocatalytic activity. The major objective of this study is to formulate a simple yet efficient photocatalyst and to explore the influence of gamma irradiation on photocatalytic water-splitting performance. A gamma-irradiated graphitic carbon nitride/silver-cadmium sulfide heterostructure composite was synthesized via microwave-assisted hydrothermal treatment, followed by melamine polymerization and gamma irradiation. It was found that enhanced photocatalytic efficiency was achieved by suppressing the charge carrier recombination, improving interfacial charge transfer, and increasing visible-light absorption. Additionally, incorporating Ag nanoparticles facilitated the formation of an S-scheme electron transfer pathway, thereby enhancing stability and catalytic performance. The hydrogen evolution rate of the gamma-irradiated composite reached 5600 µmol g-¹ h-¹, compared to 4100 µmol g-¹ h-¹ for the untreated sample. The γ-g-C3N4/Ag-CdS photocatalyst delivers a ~36% increase in hydrogen evolution rate compared to the untreated composite. Gamma irradiation enhances charge separation without introducing additional chemical reagents, while the microwave-assisted synthesis reduces reaction time and energy consumption. The use of Ag as a co-catalyst at low loading improves activity without reliance on high-cost noble metals such as Platinum. Overall, the γ-g-C3N4/Ag-CdS system exhibited a clear enhancement in photocatalytic hydrogen production, highlighting the effectiveness of gamma irradiation and S-scheme heterojunction engineering. This work provides valuable insights for the development of stable and high-performance photocatalysts for sustainable hydrogen generation. Keywords: Microwave hydrothermal method, Gamma-treated g-C3N4/Ag-CdS, Photocatalytic water splitting, S-scheme mechanism.