Bimetallic nanoparticles encapsulated within a graphitized nitrogen-doped carbon shell for efficient pH-universal electrochemical carbon dioxide reduction.

The large-scale production of carbon monoxide (CO) through electrochemical carbon dioxide (CO2) reduction reaction (eCO2RR) is a promising strategy for mitigating CO2 emissions and energy crisis. However, developing high-efficiency, cost-effective, stable, and pH-universal electrocatalysts for eCO2RR is of utmost urgency. In this study, nickel-zinc bimetallic nanoparticles encapsulated within a graphitized nitrogen-doped carbon shell (Ni3Zn-Ni3ZnC0.7@NC) were synthesized and used as robust electrocatalysts for the eCO2RR-to-CO process. The catalysts were constructed via facile annealing of a zeolitic imidazolate framework precursor with boric acid (H3BO3) as a precursor to improve the mesoporous structures for enhanced electrolyte accessibility and CO2 diffusion. Furthermore, the addition of H3BO3 before the pyrolysis process allowed carbon atoms to dissolve and diffuse in the Ni3Zn structure, forming the Ni3Zn-Ni3ZnC0.7 composite, which afforded rich exposed active sites for eCO2RR. Benefiting from the unique structure, the Ni3Zn-Ni3ZnC0.7@NC electrocatalyst exhibited high Faradaic efficiency of CO (close to 95 %) and long-term durability in alkaline, neutral, and acidic media during the entire experimental duration. Particularly, the partial current densities of CO reached approximately 375 mA cm-2 in all electrolytes. Density functional theory calculations revealed that Ni3Zn-Ni3ZnC0.7@NC exhibited an optimized binding energy for the key intermediate *COOH, efficiently suppressing the hydrogen evolution reaction while enhancing the eCO2RR-to-CO performance.