Importance of Ag–Cu Biphasic Boundaries for Selective Electrochemical Reduction of CO₂to Ethanol

Abstract

In recent years, electrochemical reduction of carbon dioxide (CO2) has received a great deal of attention due to the potential that this process can mitigate the atmospheric CO2 concentration and produce valuable organic compounds. In particular, Cu and Cu-based catalysts have exhibited the capability of converting CO2 into multicarbon fuels and chemicals in significant quantities. Here, we report a facile and cheap fabrication method for the development of an Ag-incorporated cuprous oxide (Ag-Cu2O) electrode enabling selective synthesis of ethanol via electrochemical CO2 reduction and reveal the key factor improving the ethanol (C2H5OH) selectivity. The incorporation of Ag into Cu2O leads to the suppression of hydrogen (H2) evolution, and furthermore, by varying the elemental arrangement (phase-separated and phase-blended) of Ag and Cu, we observe that C2H5OH selectivity can be controlled. Consequently, the Faradaic efficiency for C2H5OH on phase-blended Ag-Cu2O (Ag-Cu2OPB) is 3 times higher than that of the Cu2O without Ag dopant. We propose that the electrochemical reaction behavior is not solely associated with a role of Ag dopant, carbon monoxide (CO) leading to an ethanol formation pathway over ethylene, but also the doping pattern related population of Ag-Cu biphasic boundaries relatively suppresses the H2 evolution reaction and encourages the reaction of mobile CO generated on Ag to a residual intermediate on a Cu site.

Strategies in catalysts and electrolyzer design for electrochemical CO2reduction toward C2+products

“…A similar but not identical strategy has also been used to improve the electrocatalytic performance for C 2+ oxygenates (38,93,94). For instance, Ag-incorporated Cu-Cu 2 O catalysts exhibited tunable ethanol selectivity, and the highest ethanol FE was 34.15% (95). The biphasic boundary in the phase-blended Ag-Cu alloy, instead of Ag/Cu atomic ratio, was identified as the key factor for selective production of ethanol.…”

Looking Back and Looking Ahead in Electrochemical Reduction of CO2

“…We achieved tuning the selectivity toward C 2 H 5 OH over C 2 H 4 by introduction of Ag into Cu 2 O . We prepared two kinds of Ag‐incorporated bi‐phasic Cu 2 O−Cu (Ag−Cu 2 O) catalysts with different elemental mixing patterns using electrochemical co‐deposition (see Figure ).…”

“…We achieved tuning the selectivity toward C 2 H 5 OH over C 2 H 4 by introduction of Ag into Cu 2 O. [44] We prepared two kinds of Ag-incorporated bi-phasic Cu 2 OÀ Cu (AgÀ Cu 2 O) catalysts with different elemental mixing patterns using electrochemical co-deposition (see Figure 7). As a result, the higher faradaic efficiency for C 2 H 5 OH (34.15 %) was recorded at the AgÀ Cu 2 O having a phase-blended mixing pattern than those of the so-called phase-separated AgÀ Cu 2 O catalyst (20.1 %) and Cu 2 O without Ag doping (10.5 %).…”

“…XRD patterns of (a) the phase-separated Ag-Cu 2 O and (b) phaseblended Ag-Cu 2 O electrode as a function of applied potential for the electrochemical deposition. Reproduced with permission from Ref [44],. Copyright (2017), American Chemical Society.…”

Electrochemical CO2 Reduction on Bimetallic Surface Alloys: Enhanced Selectivity to CO for Co/Au(110) and to H2 for Sn/Au(110)

“…Various ways for converting CO 2 , one of the greenhouse-effect molecules, into useful valuable chemical substances, such as thermochemical catalytic reactions [1,2] and photocatalytic reactions, [3,4] have been studied to attain a CO 2 zero-emission society. The electrochemical CO 2 reduction (ECR) is an effective way to convert CO 2 to carbon monoxide (CO), [5][6][7][8] formic acid (HCOOH), [9][10][11] alcohol, [12][13][14] and various hydrocarbons. [15][16][17] Because the ECR activity and selectivity of various substance generations are crucially influenced by the electrode materials [18,19] and electrode potentials, [20,21] appropriate tuning of the ECR conditions is indispensable for CO 2 conversions with high energy efficiency.…”