Tackling the proton limit under industrial electrochemical CO₂ reduction by a local proton shuttle

Abstract Industrial CO₂ electroreduction has received tremendous attentions for resolution of the current energy and environmental crisis, but its performance is greatly limited by mass transport at high current density. In this work, an ion‐polymer‐modified gas‐diffusion electrode is used to tackle this proton limit. It is found that gas diffusion electrode‐Nafion shows an impressive performance of 75.2% Faradaic efficiency in multicarbon products at an industrial current density of 1.16 A/cm². Significantly, in‐depth electrochemical characterizations combined with in situ Raman have been used to determine the full workflow of protons, and it is found that HCO₃⁻ acts as a proton pool near the reaction environment, and HCO₃⁻ and H₃O⁺ are local proton donors that interact with the proton shuttle −SO₃⁻ from Nafion. With rich proton hopping sites that decrease the activation energy, a “Grotthuss” mechanism for proton transport in the above system has been identified rather than the “Vehicle” mechanism with a higher energy barrier. Therefore, this work could be very useful in terms of the achievement of industrial CO₂ reduction fundamentally and practically.