A Universal Principle to Accurately Synthesize Atomically Dispersed Metal-N₄ Sites for CO₂ Electroreduction

Atomically dispersed metal-nitrogen sites-anchored carbon materials have been developed as effective catalysts for CO₂ electroreduction (CO₂ER), but they still suffer from the imprecisely control of type and coordination number of N atoms bonded with central metal. Herein, we develop a family of single metal atom bonded by N atoms anchored on carbons (SAs-M-N-C, M = Fe, Co, Ni, Cu) for CO₂ER, which composed of accurate pyrrole-type M-N₄ structures with isolated metal atom coordinated by four pyrrolic N atoms. Benefitting from atomically coordinated environment and specific selectivity of M-N₄ centers, SAs-Ni-N-C exhibits superior CO₂ER performance with onset potential of - 0.3 V, CO Faradaic efficiency (F.E.) of 98.5% at - 0.7 V, along with low Tafel slope of 115 mV dec^-1 and superior stability of 50 h, exceeding all the previously reported M-N-C electrocatalysts for CO₂-to-CO conversion. Experimental results manifest that the different intrinsic activities of M-N₄ structures in SAs-M-N-C result in the corresponding sequence of Ni > Fe > Cu > Co for CO₂ER performance. An integrated Zn-CO₂ battery with Zn foil and SAs-Ni-N-C is constructed to simultaneously achieve CO₂-to-CO conversion and electric energy output, which delivers a peak power density of 1.4 mW cm^-2 and maximum CO F.E. of 93.3%.