Highly active metallic nickel sites confined in N-doped carbon nanotubes toward significantly enhanced activity of CO₂ electroreduction

Carbon dioxide electroreduction (CO₂ER)still faces the challenges of low product selectivity, high overpotential, and high cost of electrocatalysts. Herein, we develop a low-cost and highly efficient precious-metal-free CO₂ER electrocatalyst, composed of Ni nanoparticles (NPs)with the size range of 50–100 nm, confined within N-doped carbon nanotubes (NCNTs)with the diameter of 100–200 nm (Ni@NCNTs). Benefitting from the confinement effect, the resulting 1D Ni@NCNTs hybrid exhibits an exceptional electrocatalytic activity and selectivity for CO production with a relatively positive onset potential of −0.3 V, low Tafel slope of 97 mV dec⁻¹, and high Faradaic efficiency of 99.1%. The high selectivity of Ni@NCNTs for CO production during the CO₂ER is almost the best among all previously reported N-doped carbon based CO₂ER electrocatalysts. Experimental observations demonstrate that the confined Ni NPs inside NCNTs is a key step to promote the conversion of CO₂ to CO. Density functional theory calculations reveal that the confinement effect of NCNTs can weaken the binding strengths between Ni NPs and *CO intermediates, thus improving the rate-limiting step of *CO desorption during the CO₂ER process. Further integration of 1D Ni@NCNTs electrocatalyst with a solar panel or two alkaline batteries enable highly active and sustainable CO₂ER and water splitting.