Temperature-driven selectivity control in bi-catalyzed CO2 electroreduction via local alkalinity and water structure

Temperature is a key operating variable that governs both activity and selectivity in the electrochemical CO 2 reduction reaction (CO 2 RR). Here, we systematically elucidate the temperature-dependent behavior of a bismuth-based catalyst supported on carbon nanotubes (Bi-CNT) over a broad window of 303–343 K. The catalyst delivers a maximum Faradaic efficiency of 95% for formate at 318 K, accompanied by a high partial current density for formate of 285.6 mA cm −2 at a total current density of 300 mA cm −2 . By combining in-situ Raman spectroscopy with molecular dynamics simulations, we reveal that the moderate heating enhances formate selectivity through a cooperative increase in local alkalinity and a restructuring of the hydrogen‑bond network of interfacial water, which suppress the hydrogen evolution reaction. At elevated temperatures, the attenuation of local alkalinity and the growth of weakly hydrogen‑bonded water populations promote CO and H 2 formation, leading to diminished formate selectivity. These findings establish temperature‑mediated control of the interfacial microenvironment as an efficient strategy for robust, high‑rate CO 2 ‑to‑formate conversion under industrially relevant, thermally dynamic operating conditions.