Bifurcation of *COOH Pathway Determines HCOOH Formation in CO ₂ Electroreduction on Bismuth

Abstract

ABSTRACT Bismuth (Bi) is a promising electrocatalyst for the CO 2 reduction reaction (CO 2 RR) to formic acid (HCOOH), yet its mechanism remains a subject of debate. While the pathway involving the oxygen‐bound *OCHO intermediate is conventionally accepted, experimentally observed carbon‐bound species have been largely overlooked. In this work, we resolve this mechanistic ambiguity by combining constant‐potential ab initio molecular dynamics (AIMD) simulations with spectroscopic evidence. We reveal that the reaction on Bi is governed by the bifurcation of the *COOH pathway, which favors HCOOH formation over CO. We also identify an *H‐mediated pathway as an alternative route at low potentials where *CO 2 activation is suppressed. Supported by the experimental detection of *COOH, our findings suggest that this mechanism is likely a general feature across other metal surfaces, such as Ag, Cu, and In. Consequently, we bring the *COOH‐mediated mechanism to the forefront of HCOOH production, highlighting the need to consider this pathway in the rational design of future HCOOH‐selective electrocatalysts.