Coordination Reconstruction of Fe Single Atoms by Encapsulated Nickel Nanoparticles for Efficient CO ₂ Electroreduction

Coordination reconstruction of atomically dispersed active sites in electrocatalytic reactions is expected to enhance the catalytic activity, but achieving this goal remains challenging. Herein, a single-atom‒nanoparticle synergistic catalyst composed of pyridine Fe─N sites and Ni nanoparticles (NPs) encapsulated in nitrogen-doped carbon nanotubes is presented, in which the Ni NPs can reconstruct the Fe─N─C coordination structure from Fe─N₄ to Fe─N₂ through the carbon nanotube structure during the CO₂ electroreduction reaction. The catalyst exhibites a low onset potential of -0.12 V in an alkaline flow cell, with a high Faradaic efficiency for CO (FE_CO) greater than 97% over a wide potential range of -0.4--1.2 V and a maximum FE_CO of 98.7%. In situ X-ray absorption spectroscopy and infrared characterization results demonstrate that the reduction in the Fe─N coordination number during the reaction process promotes the protonation of CO₂ to form the ^*COOH intermediate and thereby significantly improves the CO₂ electroreduction performance.