Confinement of Ionic Liquids at Single-Ni-Sites Boost Electroreduction of CO₂ in Aqueous Electrolytes 

The development of strategies to enhance the electrocatalytic properties of single-atom catalysts is highly desirable, yet challenging. Here we show a versatile nanoconfined ionic liquids (ILs) design to tune the interactions between CO₂ and single-Ni-site, meanwhile create a solid/liquid interface with high CO₂ concentration for efficient CO₂ electrocatalysis. The Ni-N catalyst confined with ILs can be directly used with aqueous electrolytes to mitigate the mass transport and conductivity issues typically associated with viscous bulk ILs electrolytes. Density functional theory studies reveal that the d-band center of Ni atoms is positively shifted to the Fermi level in the presence of IL, and consequently the energy barrier of the rate-limiting step of CO₂ reduction, CO₂(g) → COOH^∗, drops significantly from 1.49 to 0.80 eV. The nanoconfined ILs intensify CO₂ conversion by showing a high CO Faradaic efficiency of above 98%, enhanced current densities up to 66.1 mA cm^-2, and robust stability over 50 h.