Promoting Hydrogen Transfer in Electrochemical CO Reduction via a Hydrogen on Demand Pathway.

The proceeding of electrochemical CO reduction reaction (CORR) requires the formation of active hydrogen species for CO protonation, while traditional catalysts fail to balance the rate of hydrogen supply and CO protonation. Herein, we propose a "hydrogen on demand" mechanism, in which the polarity of the adsorbed CO is enhanced to allow the capture of hydrogen from water without forming free hydrogen species, realizing the matching rate of hydrogen supply and CO protonation. As a proof of concept, we construct Zn-N sites modified by Se atoms, allowing the proceeding of CORR under the "hydrogen on demand" mechanism with superior efficiency. The catalyst achieves an industrial CO current of -539.7 mA cm, 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 7.6×10 h 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 CO with improved ability to acquire hydrogen species from water to facilitate the protonation process.