Dual Z-Scheme g-C₃N₄/In₂S₃/In₂O₃ for Enhanced Visible-Light H₂ Evolution and Pollutant Degradation

The design of a double Z-type heterojunction represents a promising strategy in photocatalysis to achieve superior charge carrier separation, increased light-harvesting capability, and consequently, a higher photocatalytic reaction rate. Herein, a novel ternary heterojunction with direct dual Z-scheme configuration, g-C3N4/In2S3/In2O3 photocatalyst, was synthesized using a chemical bath and facile calcination process. The XRD, SEM-EDS and XPS results confirmed the successful integration of g-C3N4, In2S3, and In2O3 with preserved crystalline phases. Photocatalytic performances of the ternary composite were evaluated via two effective routes, such as methyl orange (MO) degradation and hydrogen (H2) generation, benchmarked against the pristine g-C3N4 and the g-C3N4/In2S3 and In2S3/In2O3 binary composite, revealing that the in-situ growth of In2O3 onto the g-C3N4/In2S3 composite contributed to the remarkable enhancement of their photocatalytic activity. The photodegradation process follows the pseudo-first order reaction kinetics. The ternary g-C3N4/In2O3/In2S3 heterojunction exhibited 94.8% degradation efficiency of MO with a corresponding rate of 23.4×10-3 min-1, 4.8 times higher than the pristine g-C3N4, and excellent photocatalytic activity in five consecutive cycles. Similarly, the g-C3N4/In2S3/In2O3 heterojunction exhibited a rate constant of ~2.4 mmol h−1 g−1 for H2 generation. This superior enhancement was attributed to the dual Z-scheme charge transfer mechanism. The formation of direct dual Z-scheme heterojunction improved the light harvesting, minimized electron hole recombination, and efficiently facilitated the separation of charge carriers. This work provided a mechanistic insight for engineering multifunctional heterojunction for environmental remediation and pollutant mitigation.