Regulating the Water Dissociation on Atomic Iron Sites to Speed Up CO2 Protonation and Achieve pH‐Universal CO2 Electroreduction

Abstract Atomic Fe sites enabled electrochemical carbon dioxide (CO 2 ) reduction (ECO 2 R) to carbon monoxide (CO) at low overpotentials. However, the narrow potential ranges for selective CO 2 conversion on atomic Fe sites hindered the CO production at high current densities. Therefore, unveiling the CO 2 electroreduction processes and clarifying the catalytic mechanisms on different atomic Fe sites are important for better design of atomic Fe catalysts toward efficient ECO 2 R. Herein, the ECO 2 R processes on single‐atom, dual‐atom, and cluster Fe sites are systematically investigated, and clarify that the balanced water dissociation and CO 2 protonation on dual‐atom Fe sites promote the efficient CO production. The dual‐atom Fe catalyst achieves Faradaic efficiencies of CO ( FE CO ) above 92% over a wide potential range of −0.4–−0.9 V versus reversible hydrogen electrode and maintains FE CO of 91% after 153‐h electrolysis in H‐type cell. Benefitting from the favorable CO 2 protonation for ECO 2 R on dual‐atom Fe sites, pH‐universal CO 2 electroreduction is achieved in alkali‐/acid‐/bicarbonate‐fed membrane electrode assembly electrolyzer, with FE CO exceeds 98% in strongly acidic/alkaline and neutral mediums. The work reveals a water dissociation‐promoted CO 2 electroreduction on dual‐atom Fe sites and presents a feasible regulation of atomic Fe sites for highly active/selective ECO 2 R.