Exclusive Ni-N₄ Sites Realize Near-Unity CO Selectivity for Electrochemical CO₂ Reduction

Electrochemical reduction of carbon dioxide (CO₂) to value-added carbon products is a promising approach to reduce CO₂ levels and mitigate the energy crisis. However, poor product selectivity is still a major obstacle to the development of CO₂ reduction. Here we demonstrate exclusive Ni-N₄ sites through a topo-chemical transformation strategy, bringing unprecedentedly high activity and selectivity for CO₂ reduction. Topo-chemical transformation by carbon layer coating successfully ensures preservation of the Ni-N₄ structure to a maximum extent and avoids the agglomeration of Ni atoms to particles, providing abundant active sites for the catalytic reaction. The Ni-N₄ structure exhibits excellent activity for electrochemical reduction of CO₂ with particularly high selectivity, achieving high faradaic efficiency over 90% for CO in the potential range from -0.5 to -0.9 V and gives a maximum faradaic efficiency of 99% at -0.81 V with a current density of 28.6 mA cm^-2. We anticipate exclusive catalytic sites will shed new light on the design of high-efficiency electrocatalysts for CO₂ reduction.