A Potential-Gated Molecular Circuit with Frictionless Hydride Transfer for Formic Acid Oxidation

Abstract Direct formic acid fuel cells represent a cornerstone of the clean energy transition, yet their efficiency remains tethered to the rigid scaling relations of the formic acid oxidation reaction. Here, we demonstrate that a heteronuclear Rh–Cr dual-atom catalyst can bypass these traditional limits by operating as a potential-gated molecular circuit. Using grand-canonical ab initio molecular dynamics at the explicit aqueous interface, we observe the reaction in real time under constant-potential conditions. Our simulations reveal a remarkable division of responsibility between the two metal centers. The Cr site acts as a static anchor, spontaneously deprotonating formic acid and pinning the formate anion in a geometry that prevents the formation of carbon monoxide (CO). Meanwhile, the Rh center acts as a potential-controlled relay. It remains a spectator during initial absorption but switches on at a critical potential threshold, facilitating a near-frictionless hydride transfer with a negligible barrier of just 0.04 eV. This synergistic handshake effectively decouples intermediate stability from reaction kinetics─a feat impossible for single-site catalysts. We observe a synergetic migratory oxidation pathway, in which the Rh center, once activated, facilitates near-frictionless C–H activation and a hydride transfer. Crucially, we show that traditional constant-charge models fail to capture this circuit-like behavior, leading to artificially high barriers and a misidentification of the rate-determining step. By framing the Rh–Cr pair as a stereoselective electronic filter, this work provides a new blueprint for designing catalysts that do not just speed up reactions but also electronically steer them toward high-flux and poison-resistant pathways.