There is an urgent need to develop technologies that use renewable energy to convert waste products such as carbon dioxide into hydrocarbon fuels. Carbon dioxide can be electrochemically reduced to hydrocarbons over copper catalysts, although higher efficiency is required. We have developed oxidized copper catalysts displaying lower overpotentials for carbon dioxide electroreduction and record selectivity towards ethylene (60%) through facile and tunable plasma treatments. Herein we provide insight into the improved performance of these catalysts by combining electrochemical measurements with microscopic and spectroscopic characterization techniques. Operando X-ray absorption spectroscopy and cross-sectional scanning transmission electron microscopy show that copper oxides are surprisingly resistant to reduction and copper+ species remain on the surface during the reaction. Our results demonstrate that the roughness of oxide-derived copper catalysts plays only a partial role in determining the catalytic performance, while the presence of copper+ is key for lowering the onset potential and enhancing ethylene selectivity.
Efficient, stable catalysts with high selectivity for a single product are essential if electroreduction of CO is to become a viable route to the synthesis of industrial feedstocks and fuels. A plasma oxidation pre-treatment of silver foil enhances the number of low-coordinated catalytically active sites, which dramatically lowers the overpotential and increases the activity of CO electroreduction to CO. At -0.6 V versus RHE more than 90 % Faradaic efficiency towards CO was achieved on a pre-oxidized silver foil. While transmission electron microscopy (TEM) and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulk of the catalyst during the reaction, quasi in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. DFT calculations reveal that the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields drastically decrease the overpotential of CO electroreduction.
The
catalytic properties of bulk-immiscible alloys are less explored
than their bulk-miscible counterparts due to inherent difficulties
in their synthesis and stabilization. The development of alternative
synthetic methods can, however, provide routes toward bulk-immiscible
nanoparticles with metastable randomly alloyed structures. In this
study, we combine computational screening and a microwave-based synthesis
method to target bulk-immiscible alloys that show enhanced reactivity
over pure metals for the oxygen reduction reaction (ORR). A number
of systems are identified theoretically as promising ORR catalysts.
The theoretical predictions are experimentally verified for the RhAu
system, for which a specific surface ensemble is identified as being
highly active in the ORR.
Efficient, stable catalysts with high selectivity for a single product are essential if electroreduction of CO2 is to become a viable route to the synthesis of industrial feedstocks and fuels. A plasma oxidation pre-treatment of silver foil enhances the number of low-coordinated catalytically active sites, which dramatically lowers the overpotential and increases the activity of CO2 electroreduction to CO. At −0.6 V versus RHE more than 90% Faradaic efficiency towards CO was achieved on a pre-oxidized silver foil. While transmission electron microscopy (TEM) and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulk of the catalyst during the reaction, quasi in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. DFT calculations reveal that the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields drastically decrease the overpotential of CO2 electroreduction
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