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.