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

Abstract

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.