Promoting Hydrogen Transfer in Electrochemical CO2 Reduction via a Hydrogen on Demand Pathway

The proceeding of electrochemical CO2 reduction reaction (CO2RR) requires the formation of active hydrogen species for CO2 protonation, while traditional catalysts fail to balance the rate of hydrogen supply and CO2 protonation. Herein, we propose a "hydrogen on demand" mechanism, in which the polarity of the adsorbed CO2 is enhanced to allow the capture of hydrogen from water without forming free hydrogen species, realizing the matching rate of hydrogen supply and CO2 protonation. As a proof of concept, we construct Zn-N sites modified by Se atoms, allowing the proceeding of CO2RR under the "hydrogen on demand" mechanism with superior efficiency. The catalyst achieves an industrial CO current of -539.7 mA cm-2, faradaic efficiencies of CO > 90% over a broad window from -0.5 to -1.1 V vs. reversible hydrogen electrode and a high turnover frequency of 7.6 × 104 h-1 in flow cell. In-situ characterization and theoretical calculations reveal that the introduced Se sites enhance the electron localization around the Zn sites, thus increasing the polarity of adsorbed CO2- with improved ability to acquire hydrogen species from water to facilitate the protonation process.