Ternary heterojunctions on Zn3In2S6/C3N5 towards advancing simultaneous photocatalytic production of H2O2 and benzaldehyde

Cooperative photocatalysis for simultaneous hydrogen peroxide (H 2 O 2 ) production and organic oxidation presents a sustainable approach to solar-to-chemical energy conversion. While Zn x In 2 S x +3 materials are promising candidates, the study of high stoichiometry ( x > 1) variants is still limited. Moreover, the synergy of mixed-phase C 3 N 5 and Zn x In 2 S x +3 remains to be explored. Herein, a series of Zn x In 2 S x +3 ( x = 1–4) photocatalysts were synthesized via reflux, with Zn 3 In 2 S 6 ( x = 3) identified as the optimal composition, achieving H 2 O 2 and benzaldehyde production rates of 1430.9±65.6 μM h -1 and 2473.2±264.2 μM h -1 , respectively. CCN550 was synthesized by the molten-salt method and a ternary heterostructure (5CCN/RZIS3) was further developed by compositing Zn 3 In 2 S 6 with crystalline C 3 N 5 (CCN550) by adding CCN550 during refluxing, leading to enhanced yields of H 2 O 2 (2655.2±167.1 μM h -1 ; AQE: 1.1% at 420 nm) and benzaldehyde (2685.9±126.5 μM h -1 ). Improved performance stems from the intimate interface between Zn 3 In 2 S 6 and heptazine/triazine domains in C 3 N 5 , which facilitates efficient charge separation and boosts O 2 adsorption. Rotating disk electrode measurements confirmed high selectivity toward the two-electron oxygen reduction pathway. This study introduces a ternary heterojunction strategy and provides insights into the role of crystalline structure and heterointerface engineering in advancing dual-functional photocatalysis. • Ternary heterojunction construction based on Zn 3 In 2 S 6 and the heptazine/triazine phases of crystalline C 3 N 5 . • The performances of optimal composite (5CCN/RZIS3) surpassed most reported pieces of literature in such dual-functional systems for the co-production of H 2 O 2 and benzaldehyde. • RDE measurements demonstrated that the average number of transferred electrons (n) of 5CCN/RZIS3 is 2.01, a significant improvement over the pristine CCN550 (1.93) and Zn 3 In 2 S 6 (2.02). • Scavenger test elucidated the critical role of superoxide radical intermediate in H 2 O 2 production after confirming the one-step 2e - ORR pathway via RDE tests.