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 (FECO) of 97.9% and a CO partial current density (j CO) of -15.6 mA cm-2 at -0.92 V vs. RHE. Moreover, FECO 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.