Journal
ACS CATALYSIS
Volume 11, Issue 8, Pages 4530-4537Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.1c00338
Keywords
electrocatalysis; CO2RR; HER; solar fuels; modified electrodes; silver electrodes
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Funding
- Office of Science of the U.S. Department of Energy [DE-SC0004993]
- Marie Sklodowska-Curie Fellowship H2020-MSCA-IF2017 [793471]
- Resnick Sustainability Institute at Caltech
- Marie Curie Actions (MSCA) [793471] Funding Source: Marie Curie Actions (MSCA)
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Selective conversion of CO2 to CO with high Faradaic efficiencies (>99%) on planar silver electrodes was achieved using simple pyridinium-based additives, which form organic films altering CO2RR selectivity. Electrochemical kinetic and mechanistic data suggest that a hydrophobic organic layer inhibits hydrogen production selectively by limiting proton mass transport, while pointing to proton transfer as the rate-determining step instead of electron transfer for planar Ag electrodes.
The carbon dioxide reduction reaction (CO2RR) in aqueous electrolytes suffers from efficiency loss due to the competitive hydrogen evolution reaction (HER). Developing efficient methods to suppress HER is a crucial step toward CO2 utilization. Herein we report the selective conversion of CO2 to CO on planar silver electrodes with Faradaic efficiencies >99% using simple pyridinium-based additives. Similar to our previous studies on copper electrodes, the additives form an organic film which alters CO2RR selectivity. We report electrochemical kinetic and other mechanistic data to shed light on the role of these organic layers in suppressing HER. These data suggest that hydrogen production is selectively inhibited by the growth of a hydrophobic organic layer on the silver surface that limits proton but not CO2 mass transport at certain applied potentials. The data also point to the involvement of a proton-transfer within the rate-determining step of the catalysis, instead of the commonly observed electron-transfer step for the case of planar Ag electrodes.
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