Density-dependent lattice dispersion of Sn on Cu inverts selectivity in CO2 electroreduction from CO to formate

Tuning Sn dispersion switches CO 2 RR path, challenging site-activity dogma • Low Sn dispersion density highly stabilizes *OCHO, strongly favoring it over *COOH • 89.3% formate FE at 200 mA cm −2 under flow-cell conditions surpasses prior reports • Catalyst reconstruction and reaction species are analyzed by in situ experiments Electrocatalytic CO 2 reduction to CO and formate holds significant industrial promise. Herein, we reveal that the surface density of atomically dispersed Sn on Cu lattice modulates the active-site identity from Cu to Cu Sn, thereby switching product distributions. L-Sn 1 -Cu, featuring sparse Sn coverage, achieves a CO Faradaic efficiency (FE) of 72.8% at a current density of 300 mA cm −2 . Conversely, H-Sn 1 -Cu with saturated Sn isolation attains a formate FE of 89.3% at a current density of 200 mA cm −2 . Operando spectroscopy and DFT calculations show that Sn-deficient locales expose Cu atoms to bind *COOH and favor CO formation, while Sn-congested domains create polarized Cu Sn pairs that lock *OCHO for formate synthesis. This density-dependent ensemble tuning enables switchable selectivity between CO and formate in CO 2 electroreduction at industrially relevant current densities. By precisely tuning the lattice dispersion density of single-atom Sn on Cu, this work achieves a programmable selectivity inversion from *COOH-mediated CO production on sparse Sn sites to *OCHO-stabilized formate synthesis via polarized Cu Sn ensembles at industrially relevant current densities. Download: Download high-res image (54KB) Download: Download full-size image