Overlooked roles of high-valence Sn in SnS2 loaded on gC3N4 for enhanced photocatalytic H2O2 production: Mechanism, DFT, and techno-economic analysis study

Abstract

Solar-driven photocatalysis with charge-transfer modulation is a green approach for enhancing the oxygen reduction reaction (ORR) to generate hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>). In this study, we introduced a novel method for synthesizing high-valence Snδ+ in SnS<inf>2</inf>, combined with gC<inf>3</inf>N<inf>4</inf> to create gC<inf>3</inf>N<inf>4</inf>/SnS<inf>2</inf>. Density functional theory (DFT) calculations exhibited that the interface between SnS<inf>2</inf> and gC<inf>3</inf>N<inf>4</inf> creates interband states through strong hybridization, revealing that photoexcited electrons flowed from C in gC<inf>3</inf>N<inf>4</inf> to S in SnS<inf>2</inf>, forming a Z-scheme heterojunction. The optimal gC<inf>3</inf>N<inf>4</inf>/SnS<inf>2</inf>-2 (2% SnS<inf>2</inf> loaded) achieved a high H<inf>2</inf>O<inf>2</inf> production rate of 7.186 mmol g−1 h−1 and an apparent quantum efficiency (AQE) of 33.8% at 405 nm with isopropanol (IPA), converting 88.8% IPA to acetone in 2 h. The gC<inf>3</inf>N<inf>4</inf>/SnS<inf>2</inf> composite improved the charge transfer resistance and elongated the non-radiative electron decay time. Notably, SnS<inf>2</inf> doping of gC<inf>3</inf>N<inf>4</inf> decreased the antibonding orbital occupancy and lowered the energy barrier for O<inf>2</inf> and OOH* adsorption. In situ surface-enhanced Raman spectroscopy (SERS) analysis confirmed the generation of OOH* on gC<inf>3</inf>N<inf>4</inf>/SnS<inf>2</inf> during light irradiation. A techno-economic analysis (TEA) was conducted to evaluate the economic viability of photocatalytic H<inf>2</inf>O<inf>2</inf> production, revealing that it was not economically feasible owing to challenges in the separation process. This study provides unique perspectives on the approaches to inducing a high valence state of Snδ+ for enhancing photocatalytic H<inf>2</inf>O<inf>2</inf> generation and the challenge of commercializing H<inf>2</inf>O<inf>2</inf> production via photocatalysis. © 2025 Elsevier B.V., All rights reserved.