Synthesis and Catalytic Activity of Nitrogen-Doped End-Sealed Carbon Nanotube Nanoclusters for Electrocatalytic CO₂ Reduction

The electrocatalytic reduction of carbon dioxide presents a highly promising method for transforming greenhouse gas CO₂ into valuable carbon CO derivatives, simultaneously facilitating the utilization of renewable energy sources. In this study, we developed a nitrogen-doped carbon nanotube (CNT) electrocatalyst with end-capped nanoparticles (5NiNPSN@HCNT-800), fabricated by controlling metal size reduction via pyrolysis and subsequent acid leaching. These modifications remarkably enhanced the catalyst’s efficiency for CO₂ reduction. After acid leaching, in an H-cell, operating at potentials between −0.6 and −1.1 V relative to reversible hydrogen electrode (RHE), FE_CO > 95%, with a partial current density for CO reaching 29.83 mA/cm², while C_dl increased significantly from 16.36 to 79.04 mF/cm². The enhancement is ascribed to the reduced metal nanoparticle size, which together increases the active surface area for CO₂RR and decreases charge transfer resistance. It facilitates the generation of CO₂ intermediates while inhibiting the hydrogen evolution reaction (HER), thus enhancing the kinetics of CO₂ reduction. This research is anticipated to offer crucial insights for the development and large-scale implementation of carbon dioxide electrocatalysts.