Establishing spatially elastic hydrogen-bonding interaction in electrochemical process for selective CO2-to-CH4 conversion

In a CO2 electroreduction reaction, accurately acquiring the variations of coordination microenvironment around the catalytic sites in the electrochemical process is extremely important to promote product (especially hydrocarbons) selectivity and explain the related catalytic reaction mechanism. In this work, we elaborately design and construct a simple and stable crystalline Cu-based supramolecular structure model system (including Cu-TPP, Cu-2TPyP, Cu-3TPyP, and Cu-4TPyP), in which the spatially elastic hydrogen-bonding interaction between pyridine nitrogen atom and hydrogen-donating substances (∗COOH) can be established in the electrochemical process by adjusting the position of pyridine nitrogen atoms in molecules. Based on this well-defined catalyst model system, we systematically studied the influences of variations of a spatially elastic hydrogen-bonding microenvironment on improving the CO2-to-CH4 electroreduction performance. Experimental and theoretical calculation results show that subtle changes of the hydrogen-bonding interaction in the electrochemical process can affect the adsorption energy of ∗COOH, thus the faradic efficiency for CH4 (FECH4) can be improved from 32.3% to 62.4%.