Balanced ElectronDonation Governs Adsorption SiteSelection in CO2 Electroreduction to HCOOH on TransitionMetal-Doped Magnesium Oxides

Magnesium oxide (MgO) is attractive for CO2 utilization, because interaction with O2. However, the electronic inertness has limited its application in electrochemical catalysis. Herein, spin-polarized dDFT calculations with the BEEF-vdW functional were performed to evaluate the activity and selectivity of transition-metal-doped MgO (TM-MgO) catalysts for electrochemical CO2 reduction (eCO2RR). Co-, Pd-, and Pt-doped MgO were identified as promising candidates for selective formic acid (HCOOH) production. Mechanistic analysis shows that TM doping induces electron redistribution in MgO, activating neighboring Mg sites while enabling charge transfer between TM dopants and reaction intermediates. The competition between Mg-site activation and TM-intermediate charge transfer determines the site preference and binding strength of the key OCHO* intermediate. Bader charge, density of states, and COHP analyses support this mechanism. This work provides design principles for oxide-based electrocatalysts toward selective HCOOH production from eCO2RR.