Mass transfer regulation via porous structure engineering of molecular catalysts for enhanced electrochemical CO2 reduction

Achieving highly selective CO synthesis at near-ampere current densities (>500 mA cm −2 ) is pivotal for the industrialization of the electrochemical CO 2 reduction reaction (ECO 2 RR). However, the intrinsic low solubility of CO 2 and sluggish mass transfer kinetics fail to sustain rapid CO generation, which hinders the attainment of high current densities and renders traditional active-site regulation strategies ineffective. Thus, enhancing local CO 2 concentration and optimizing mass transfer has emerged as an urgent prerequisite for developing high-performance ECO 2 RR catalysts. To address this unmet need, we rationally designed a novel catalyst by immobilizing molecularly dispersed cobalt phthalocyanine (CoPc) onto hollow carbon spheres with tailored porous architectures. The confinement effect of the hollow porous structure boosts local concentrations of CO 2 and reaction intermediates, while structural engineering of pore parameters optimizes mass transfer efficiency and balances the density of active sites. Molecular dynamics simulations reveal that enlarging pore diameter and shortening pore length modulate the flow rate and distribution of CO 2 and electrolyte, accelerating reactant transport to active sites and promoting rapid product desorption, thereby facilitating mass transfer. Ultimately, these structural optimizations enable a CO Faradaic efficiency exceeding 92% at a near-ampere-level current densities of 800 mA cm −2 , and a turnover frequency as high as 86 s −1 , along with robust performance over a wide current density range of 100–800 mA cm −2 , outperforming state-of-the-art ECO 2 RR catalysts. This work provides a feasible mass transfer regulation strategy, offering new insights for improving ECO 2 RR current density and product selectivity, and laying a foundation for the industrial application of ECO 2 RR.