Nature Chemistry, Published online: 07 September 2026; doi:10.1038/s41557-026-02243-1 Electrochemical CO2 reduction is typically constrained by proton-coupled electron transfer, which couples CO2 conversion with competing H2 evolution. Now it has been shown that a Janus palladium membrane electrode enables selective formate production through heterogeneous hydride transfer, providing access to electrochemical hydride-based reactivity beyond proton-mediated electrocatalysis.