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Enhancing CO2 Electroreduction to Ethanol on Copper–Silver Composites by Opening an Alternative Catalytic Pathway
journal contribution
posted on 2020-03-16, 11:35 authored by Louisa
Rui Lin Ting, Oriol Piqué, Si Ying Lim, Mohammad Tanhaei, Federico Calle-Vallejo, Boon Siang YeoA fundamental
question in the electrochemical CO2 reduction
reaction (CO2RR) is how to rationally control the catalytic
selectivity. For instance, adding a CO-selective cocatalyst like Ag
to Cu shifts the latter’s CO2RR selectivity toward
C2 products, but the underlying cause of the change is
unclear. Herein, we show that, during CO2RR, the abundant
CO availability at Cu−Ag boundaries facilitates C-C coupling
on Cu to selectively generate ethanol through an otherwise closed
pathway. Oxide-derived Cu nanowires mixed with 20 nm Ag particles
(Cu:Ag mole ratio of 1:20) catalyzed CO2 reduction to ethanol
with a maximum current density of −4.1 mA/cm2 and
ethanol/ethylene Faradaic efficiency ratio of 1.1 at −1.1 V
vs RHE. These figures of merit are, respectively, 5 and 3 times higher
than those for pure oxide-derived Cu nanowires. CO2RR on
CuAg composite catalysts with different Ag:Cu ratios and Ag particle
sizes reveals that ethanol production scales with the amount of CO
evolved from Ag sites and the abundance of Cu–Ag boundaries,
and, very interestingly, without significant modifications to ethylene
formation. Computational modeling shows selective ethanol generation
via Langmuir–Hinshelwood *CO + *CHx (x = 1, 2) coupling at Cu–Ag boundaries
and that the formation of energy-intensive CO dimers is circumvented.
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CO 2 reductionAlternative Catalytic PathwayC-COxide-derived Cu nanowiresEnhancing CO 2 ElectroreductionRHEethylene formationenergy-intensive CO dimersCO-selective cocatalystC 2 products3 timesCO availabilityCu shiftsCO 2 RRComputational modelingoxide-derived Cu nanowireselectrochemical CO 2 reduction reactionAg sites20 nm Ag particlesethanol production scalesAg particle sizesethanol generationCH x
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