Multivalent Cu sites synergistically adjust carbonaceous intermediates adsorption for electrocatalytic ethanol production.

Abstract

Copper (Cu)-based catalysts show promise for electrocatalytic CO₂ reduction (CO₂RR) to multi-carbon alcohols, but thermodynamic constraints lead to competitive hydrocarbon (e.g., ethylene) production. Achieving selective ethanol production with high Faradaic efficiency (FE) and current density is still challenging. Here we show a multivalent Cu-based catalyst, Cu-2,3,7,8-tetraaminophenazine-1,4,6,9-tetraone (Cu-TAPT) with Cu²⁺ and Cu⁺ atomic ratio of about 1:2 for CO₂RR. Cu-TAPT exhibits an ethanol FE of 54.3 ± 3% at an industrial-scale current density of 429 mA cm^-2, with the ethanol-to-ethylene ratio reaching 3.14:1. Experimental and theoretical calculations collectively unveil that the catalyst is stable during CO₂RR, resulting from suitable coordination of the Cu²⁺ and Cu⁺ with the functional groups in TAPT. Additionally, mechanism studies show that the increased ethanol selectivity originates from synergy of multivalent Cu sites, which can promote asymmetric C-C coupling and adjust the adsorption strength of different carbonaceous intermediates, favoring hydroxy-containing C₂ intermediate (*HCCHOH) formation and formation of ethanol.