Takhar, VishakhaVishakhaTakharBarman, MadhurimaMadhurimaBarmanDutta, ArnabArnabDuttaBanerjee, RupakRupakBanerjee2025-08-312025-08-312025-01-0110.1002/smll.2025052932-s2.0-105012767175https://d8.irins.org/handle/IITG2025/28366Developing bifunctional electrocatalysts capable of efficiently driving the interconversion between oxygen and water molecules via oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for establishing renewable-driven energy infrastructure. A series of lead-free halide perovskites Cs<inf>2</inf>SnX<inf>6</inf> (X = Cl, Br, I) is designed, along with their mixed halide derivatives Cs<inf>2</inf>SnCl<inf>x</inf>Br<inf>6-x</inf> (where x = 2, 3, 4), to probe bifunctional OER/ORR activity. Measurements reveal the influence of halide ions on the morphology and unravel the unique halide-electronegativity-tunable electronic properties. Further, these materials are immobilized on carbon paper and utilized as anode, where Cs<inf>2</inf>SnCl<inf>6</inf> and Cs<inf>2</inf>SnCl<inf>2</inf>Br<inf>4</inf> displayed the best OER activity and appreciable Faradic efficiency. The photophysical properties of the perovskites lead to a distinct enhancement (≈0.24–0.72 mA cm⁻²) in the OER current response for Cs<inf>2</inf>SnCl<inf>6</inf> and Cs<inf>2</inf>SnCl<inf>2</inf>Br<inf>4</inf> under white-light irradiation. The perovskites maintain their structural and chemical integrity during the (photo)electrocatalysis, as demonstrated by in-depth post-electrolytic surface analysis. The electrocatalysts continue to demonstrate active ORR during the cathodic scan (onset potential of ≈0.6 V vs RHE); however, with minimal influence of photoirradiation. Overall, the Cs<inf>2</inf>SnX<inf>6</inf>-based perovskite electrocatalysts exhibit promising bidirectional OER/ORR activity with competitive catalytic efficiency and stability, suitable for developing sustainable devices for O<inf>2</inf>/H<inf>2</inf>O redox chemistry-mediated energy transduction applications.falsebidirectional photo-electrocatalysis | halide-modulated photophysical properties | lead-free halide perovskites | oxygen evolution reaction | oxygen reduction reactionArticle1613682920250arJournal0WOS:001547837800001