Constructing a double Type-II g-C₃N₄/CdS/MoS₂ (GCSM) heterojunction with dual-enhanced redox capability for efficient photocatalytic pollutant degradation

Abstract Designing efficient photocatalysts with directional charge transfer pathways and long-lived charge carriers is crucial for enhancing photocatalytic performance under visible light irradiation. In this study, a novel double Type-II g-C 3 N 4 /CdS/MoS 2 (GCSM) heterojunction was rationally constructed to synergistically improve the photocatalytic degradation of methylene blue (MB) by g-C 3 N 4 . Among the synthesized composites, GCSM with a molar ratio of 1:1:2 exhibited the highest photocatalytic activity, with degradation efficiencies 16.60, 3.15 and 4.69 times higher than those of pristine g-C 3 N 4 , CdS and MoS 2 , respectively. Notably, after four consecutive cycles, the degradation efficiency of MB remained as high as 91.64%, indicating excellent catalytic stability of the ternary heterojunction. Detailed experimental investigations combined with density functional theory calculations revealed that the enhanced photocatalytic performance originates not only from the efficient charge separation and transfer facilitated by the intimate interfacial contact, but also from the synergistic interactions between CdS and MoS 2 , which promote directional migration and utilization of photogenerated charge carriers. Based on these findings, a possible photocatalytic mechanism is proposed. This work provides both theoretical insights and practical guidance for the rational design of multi-interface synergistic photocatalytic systems, offering promising prospects for high-efficiency solar energy conversion.