Kirkendall effect triggered by trace Mn element on a Ni–N–C catalyst for enhanced electroreduction of CO2 to CO

Abstract

Nitrogen-doped carbon–metal single-atom catalysts (M–N–C) derived from metal–organic frameworks (MOFs) seem promising for electrocatalytic carbon dioxide reduction. In recent years, various strategies have been developed to improve the activity of metal sites. However, these methods can make catalyst preparation complicated and usually solve only single issues. Herein, we constructed a trace Mn-doped nickel–nitrogen–carbon catalyst (Ni_Mn–N–C) by introducing only two metal elements into the precursor, where Ni–N_X serves as an active site and Mn mainly acts as a structural additive. The introduction of trace Mn triggers the Kirkendall effect and optimizes the physical structure and surface chemical state of the catalyst, thus stimulating the potential of Ni sites for the CO₂RR. Benefiting from the better exposure of active sites, improved mass transmission, lower valence Ni active species and the favorable CO₂ adsorption capacity, Ni_Mn–N–C exhibits superior CO selectivity with a faradaic efficiency higher than 90% over a wide potential range from −0.62 to −1.02 vs. RHE, while the CO partial current density is significantly improved. This work provides a simple but effective strategy for designing high-performance electrocatalysts using the Kirkendall effect.