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

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-Ni₃ZnC_0.7@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-Ni₃ZnC_0.7 composite, which afforded rich exposed active sites for eCO₂RR. Benefiting from the unique structure, the Ni₃Zn-Ni₃ZnC_0.7@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-Ni₃ZnC_0.7@NC exhibited an optimized binding energy for the key intermediate *COOH, efficiently suppressing the hydrogen evolution reaction while enhancing the eCO₂RR-to-CO performance.