Berry flux control enabled selectivity switching in electrocatalytic CO2 reduction by chiral antiferromagnets

Controlling the products of catalytic reactions underlies much of chemical processing. Here we present a novel topological strategy for the selective electrocatalytic reduction of CO2 (CO2RR) using an external magnetic field as a tuning knob. We show that modest in-plane magnetic fields trigger a topological transition in the chiral antiferromagnetic kagome metals, Mn3Ge and Mn3Sn, shifting their Berry flux (denoted as γ) from a trivial (γ = 0) to a non-trivial (γ = ±2π) state. This transition dynamically redirects CO2RR selectivity from two-electron products (CO, HCOOH) to the more kinetically demanding eight-electron product (CH4), with Faradaic efficiencies exceeding 80%. This phenomenon is corroborated by anomalous Hall measurements and density functional theory, both revealing a direct correlation between Berry flux and CO2RR selectivity. Thus, our findings establish quantum electronic topology, here the Berry flux, as a reversible, field-tunable means of controlling catalytic performance, introducing a new paradigm for adaptive electrocatalysis and real-time modulation of reaction pathways in quantum materials.