Ni-Electrocatalytic CO₂ Reduction Toward Ethanol.

Abstract

The electroreduction of CO₂ offers a sustainable route to generate synthetic fuels. Cu-based catalysts have been developed to produce value-added C₂₊ alcohols; however, the limited understanding of complex C-C coupling and reaction pathway hinders the development of efficient CO₂-to-C₂₊ alcohols catalysts. Herein, a Cu-free, highly mesoporous NiO catalyst, derived from the microphase separation of a block copolymer, is reported, which achieves selective CO₂ reduction toward ethanol with a Faradaic efficiency of 75.2% at -0.6 V versus RHE. The dense mesopores create a favorable local reaction environment with CO₂-rich and H₂O-deficient interfaces, suppressing hydrogen evolution and maximizing catalytic activity of NiO for CO₂ reduction. Importantly, the C₁-feeding experiments, in situ spectroscopy, and theoretical calculations consistently show that the direct coupling of *CO₂ and *COOH is responsible for C-C bond formation on NiO, and subsequent reduction of *CO₂-COOH to ethanol is energetically facile through the *COCOH and *OC₂H₅ pathway. The unconventional C-C coupling mechanism on NiO, in contrast to the *CO dimerization on Cu, is triggered by strong CO₂ adsorption on the polarized Ni²⁺-O^2- sites. The work not only demonstrates a highly selective Cu-free Ni-based alternative for CO₂-to-C₂₊ alcohols transformation but also provides a new perspective on C-C coupling toward C₂₊ synthesis.