Mesoporous Engineering of Single‐Atom Catalyst for Industry‐Level Electrocatalytic CO ₂ Reduction in Membrane Electrode Assemblies

Abstract Atomically dispersed transition metals anchored on nitrogen‐doped carbon have emerged as highly promising electrocatalysts for the electrochemical CO 2 reduction to CO. However, their industrial‐scale application in membrane electrode assemblies (MEAs) is limited by inadequate Faraday efficiency (FE) and long‐term stability. Herein, we propose a rational mesoporous engineering approach for Ni‐NC catalysts via a two‐step space‐confinement pyrolysis strategy. Through cryo CO‐pulse chemisorption, real‐time observations of CO 2 gas bubble diffusion, and finite element simulations, we demonstrate that the mesoporous structured Ni‐NC (meso‐Ni‐NC) exhibits significantly enhanced active site accessibility and mass transport capabilities compared to microporous structured Ni‐NC (micro‐Ni‐NC). More importantly, the mesoporous engineering enhances the internal gas‐holding capacity of the catalytic layer, effectively mitigating flooding and salt deposition and thus enhancing the catalyst's long‐term stability. Consequently, meso‐Ni‐NC achieves an industrially relevant CO partial current density of 291.8 mA cm −2 at 97.3% CO Faradaic efficiency (FE CO ), along with stable operation for 136 h at 100 mA cm −2 while maintaining FE CO exceeding 90% in an MEA, outperforming those of micro‐Ni‐NC and representing an advancement over existing state‐of‐the‐art Ni‐based single‐atom catalysts. This work highlights the critical role of pore structure in determining the performance of industry‐level electrocatalytic CO 2 reduction.