The need to sequester CO2 and return atmospheric CO2 levels to pre-industrial revolution era levels is of paramount importance and a grand challenge being tackled by today’s world-class researchers. One leading initiative to do this is via the sustainable electrochemical conversion of CO2 to fuels and high-value products (the former product being a way of making carbon neutral fuels). Despite its promise, conversion of CO2 to high-value products (i.e. 2-carbon products such as ethylene) has been challenged by poor conversion efficiency. This can be attributed to sluggish kinetics and mass transport restrictions due to the relatively low solubility (~34.2 mmol/L) and diffusivity (~2x10-9 m2/s) of CO2 in the liquid electrolyte.1 Once CO2 is depleted at the electrode surface, which can occur at modest overpotentials (~-0.6 V vs RHE) in active CO2 electrocatalysts, the hydrogen evolution reaction can quickly become the dominant reaction. We present a working model that simulates the mass transport of chemical species involved in the electrochemical reduction of CO2 (ERCO2) and acid-base reactions through reported high-activity Cu nanowires. Considerations produced from this model were then used to engineer a Cu foam based nanocatalyst that demonstrated 3-fold improvement for CO2 consumption rates per geometric area while maintaining similar CO faradaic efficiency. Ultimately, we demonstrate the need for careful design of microstructure when fabricating electrocatalysts for ERCO2.

Modelling and overcoming mass transport limits during electrochemical CO2 reduction

2019 Fall National Meeting

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