A local proton-transport promoter for industrial CO2 electroreduction to multicarbon products†

The industrial electrochemical carbon dioxide reduction reaction (eCO₂RR) is of wide interest; however, it is a great challenge to ensure sufficient and fast mass supply to achieve industrial-level current densities. Herein, a local proton-transport promoter was developed by hybridizing Cu catalytic sites with proton hopping sites from dual-conductive polymers to tackle the mass-diffusion limitation. The as-prepared Cu/polypyrrole composite exhibits an extraordinary eCO₂RR to C₂₊ performance with a high FE_C2+ of 80.0% under an industrial current density of 700 mA cm⁻². Experimentally and theoretically, it was found that protons transfer via the Grotthuss mechanism, and proton conductivity is determined by the hydrogen bond formation and breakage (“–HN¹⋯H N²H–” to “–HN¹ H⋯N²H–”) at the hopping site in dual-conductive polypyrrole, rather than the diffusion coefficient of the proton source and hydrous/anhydrous protons. Significantly, the advantageous proton transport of Cu/PPy was further confirmed using in situ scanning electrochemical microscopy based on the proton change in the diffusion layer and local catalytic sites.