The electrochemical reduction of CO2 over transition-metal catalysts is one of the sustainable routes for producing high-value hydrocarbons and energy-dense chemical fuels. Among many single-component catalysts, Cu is the only material known to produce multi-carbon (CO2+) products with appreciable selectivity. However, the generation of C2+ products competes with the formation of C1 products and the reduction of water to hydrogen. Here, we tuned the water activity (aw) by using a NaClO4-based water-in-salt-electrolyte (WiSE) with concentrations ranging from 1m to 17m, enabling the aw to be tuned from 0.97 to 0.47. As a result, commercial Cu-nanoparticle electrodes evaluated in nominally-pH 9 NaClO4 with a water activity of 0.66 achieved a Faradaic Efficiency of ~73% for C2+ products (ethylene, ethanol, and propanol) with a C2+ partial current density of -110 mA cm–2 at –0.88 vs. reversible hydrogen electrode (RHE). In this talk, we will discuss the role of electrolyte modification in enhancing the electrochemical reduction of CO2 to multi-carbon products.

The electrochemical reduction of CO~2~ over transition-metal catalysts is one of the sustainable routes for producing high-value hydrocarbons and energy-dense chemical fuels. Among many single-component catalysts, Cu is the only material known to produce multi-carbon (CO~2+~) products with appreciable selectivity. However, the generation of C~2+~ products competes with the formation of C~1~ products and the reduction of water to hydrogen. Here, we tuned the water activity (a~w~) by using a NaClO~4~-based water-in-salt-electrolyte (WiSE) with concentrations ranging from 1m to 17m, enabling the a~w~ to be tuned from 0.97 to 0.47. As a result, commercial Cu-nanoparticle electrodes evaluated in nominally-pH 9 NaClO~4~ with a water activity of 0.66 achieved a Faradaic Efficiency of ~73% for C~2+~ products (ethylene, ethanol, and propanol) with a C~2+~ partial current density of -110 mA cm^–2^ at –0.88 vs. reversible hydrogen electrode (RHE). In this talk, we will discuss the role of electrolyte modification in enhancing the electrochemical reduction of CO~2~ to multi-carbon products.

Promoting Cu-Catalyzed CO2 electroreduction to multi-carbon products by tuning the activity of water

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