Recently, efforts have been devoted to the development of CO2 electrolysis devices that can be operated at industrially relevant rates; however, limited progress has been made, especially for valuable C2+ products. In this presentation, we will present our recent work on nanoporous copper as a CO2 reduction catalyst and its integration into a microfluidic CO2 flow cell electrolyzer [1]. The CO2 electrolyzer exhibited a current density of 653 mA/cm2 with a C2+ product selectivity of ~62% at an applied potential of -0.67 V (vs. reversible hydrogen electrode). The highly porous electrode structure facilitated rapid gas transport across the electrode-electrolyte interface at high current densities. Further investigations on electrolyte effects revealed that the surface pH value was substantially different from the pH of bulk electrolyte, especially for non-buffering near-neutral electrolytes when operating at high currents. In addition to CO2 electrolysis, CO electrolysis has also been reported to yield enhanced multi-carbon (C2+) Faradaic efficiencies up to ~55% but only at low reaction rates. This is due to the low solubility of CO in aqueous electrolytes and operation in batch-type reactors. In a recent study, we constructed a high-performance CO flow electrolyzer with a well-controlled electrode-electrolyte interface that can reach total current densities up to 1 A/cm2 together with improved C2+ selectivities [2]. Computational transport modelling and isotopic C18O reduction experiments suggest that the enhanced activity is due to a higher surface pH under CO reduction conditions, which facilitated the production of acetate. At optimal operating conditions, we achieved a C2+ Faradaic efficiency of ~91% with a C2+ partial current density over 630 mA/cm2. Further investigations show that maintaining an efficient triple-phase boundary at the electrode-electrolyte interface is the most critical challenge to achieving a stable CO/CO2 electrolysis process at high rates.

Carbon utilization using electrochemical approaches

2019 Spring National Meeting

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