Abstract
Significance
Using electricity to reduce CO
2
or CO back into valuable liquid fuels can revolutionize the way we produce chemicals/fuels. However, there are two types of impurity challenges involved: Different liquid products were typically cogenerated on Cu catalysts; in addition, those generated liquid fuels were inevitably mixed with ion impurities in liquid electrolytes. By integrating the rational design of Cu nanocube catalyst and porous solid electrolyte reactor, we report a direct and continuous generation of high-purity acetic acid solutions via electrochemical CO reduction.
Electrochemical CO
2
or CO reduction to high-value C
2+
liquid fuels is desirable, but its practical application is challenged by impurities from cogenerated liquid products and solutes in liquid electrolytes, which necessitates cost- and energy-intensive downstream separation processes. By coupling rational designs in a Cu catalyst and porous solid electrolyte (PSE) reactor, here we demonstrate a direct and continuous generation of pure acetic acid solutions via electrochemical CO reduction. With optimized edge-to-surface ratio, the Cu nanocube catalyst presents an unprecedented acetate performance in neutral pH with other liquid products greatly suppressed, delivering a maximal acetate Faradaic efficiency of 43%, partial current of 200 mA⋅cm
−2
, ultrahigh relative purity of up to 98 wt%, and excellent stability of over 150 h continuous operation. Density functional theory simulations reveal the role of stepped sites along the cube edge in promoting the acetate pathway. Additionally, a PSE layer, other than a conventional liquid electrolyte, was designed to separate cathode and anode for efficient ion conductions, while not introducing any impurity ions into generated liquid fuels. Pure acetic acid solutions, with concentrations up to 2 wt% (0.33 M), can be continuously produced by employing the acetate-selective Cu catalyst in our PSE reactor.