Selective CO₂ electroreduction to ethanol on encapsulated nickel nanoparticles by N-doped carbon nanotubes

The electrosynthesis of ethanol by CO₂ reduction is mostly achieved on metallic copper electrocatalysts, but confronts low Faradic efficiency (FE) and selectivity. Herein, we report novel electrocatalysts in which Ni nanoparticles are encapsulated in N-rich carbon nanotubes (Ni@NCNT) by chemical vapor deposition method. The optimized Ni@NCNT-700 exhibits a high ethanol FE of 38.5% at −0.5 V and remains over 30% in a wide potential range of −0.5 ∼ −1.2 V. Notably, ethanol is the only liquid product and the total FE for CO and ethanol keeps above 90% in a potential range of −0.6 ∼ −1.2 V vs. reversible hydrogen electrode. A high current density of 128 mA cm⁻² is obtained in a 1 M KOH electrolyte at −2.0 V in a flow-cell device. Moreover, In-situ Raman and density functional theory calculations demonstrate that the confinement and synergistic effects of Ni NPs and NCNTs sufficiently lower the energy barrier for C–C coupling and suppressed the *CO desorption.