Nanoconfined Ionic Liquids Enhance CO2 Electroreduction in Ordered Hierarchical Porous Single-Atom Ni Catalysts

Abstract

Single-atom catalysts (SACs) are promising for the electrochemical carbon dioxide reduction reaction (CO2RR) owing to their maximum metal utilization and well-defined active sites. However, the low density of active sites and inadequate mass transport limit their electrocatalytic performance. Here, we report a highly ordered hierarchical porous Ni SAC incorporating nanoconfined ionic liquids (ILs) for CO2RR. The interconnected macropores and mesopores provide efficient transport pathways, while hydrophobic ILs nanoconfined within the microporous network enhance local CO2 availability. The hybrid catalyst delivers nearly unity CO Faradaic efficiency and enhanced partial current densities up to 32 mA cm–2, outperforming conventional Ni–N–C catalysts by 220%. Moreover, its ability to maintain high activity under diluted CO2 conditions further supports enhanced local CO2 availability enabled by the nanoconfined ILs. Operando and in situ spectroscopies suggest enhanced catalytic engagement of Ni sites and significantly enhanced mass transfer enabled by the hierarchical porous structure and nanoconfinement of ILs. Density functional theory calculations further reveal that the ILs modulate the electronic structure of Ni sites and lower the formation energy of the key intermediates. This synergistic integration of hierarchical porosity and local microenvironment engineering offers a viable pathway for advancing high-performance electrocatalysis.