Partial thermal atomization of residual Ni NPs in single-walled carbon nanotubes for efficient CO2 electroreduction

Abstract

CO₂ electroreduction (CO₂RR) is an important solution for converting inert CO₂ into high value-added fuels and chemicals under mild conditions. The decisive factor lies in the rational design and preparation of cost-effective and high-performance electrocatalysts. Herein, we first prepare a novel f-SWNTs-650 catalyst via a facile partial thermal atomization strategy, where the residual Ni particles in single-walled carbon nanotubes (SWNTs) are partially converted into atomically dispersed NiN₄ species. CO₂RR results show that the competitive evolution hydrogen reaction (HER) predominates on pristine SWNTs, while f-SWNTs-650 switches the CO₂ reduction product to CO, achieving a CO faradaic efficiency (FE_CO) of 97.9% and a CO partial current density (j_CO) of −15.6 mA cm⁻² at −0.92 V vs. RHE. Moreover, FE_CO is higher than 95% and j_CO remains at −10.0 mA cm⁻² at −0.82 V vs. RHE after 48 h potentiostatic electrolysis. Combined with systematic characterization and density functional theory (DFT) calculations, the superior catalytic performance of f-SWNTs-650 is attributed to the synergistic effect between the NiN₄ sites and adjacent Ni NPs, that is, Ni NPs inject electrons into NiN₄ sites to form electron-enriched Ni centers and reduce the energy barrier for CO₂ activation to generate the rate-limiting *COOH intermediate, thus implementing the efficient electroreduction of CO₂.