(521t) Tuning Product Selectivity of Electrochemical CO2 Reduction in Acid Electrolyte Using Cu Nanoparticles on Surfactant-Treated Carbon

Electrocatalytic CO₂ reduction reaction (CO2RR) is a viable method to recycle CO₂ into valuable products. Neutral or alkaline electrolytes have commonly been used for CO2RR to prevent hydrogen evolution reaction. However, the availability of CO₂ is limited by the homogeneous equilibrium reactions under those conditions, which consume available CO₂ for CO2RR and decrease the theoretical carbon efficiency. Lower pH electrolytes can avoid this issue and enable industrially relevant carbon efficiencies, but appreciable selectivity for CO2RR over HER can only be achieved under these conditions by utilizing gas diffusion layer flow cells. A few recent studies show promising results for CO2RR in acid using flow cells, but it is unclear how standard electrocatalyst preparation methods will translate from neutral/alkaline conditions to the acid case. We therefore investigate surfactant-mediated synthesis methods on the impact of CO2RR performance in acid electrolytes.

We synthesized Cu nanoparticles on carbon black in ethylene glycol using different types of surfactants – hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and triton X-100, which represents cationic, anionic, and nonionic surfactants, respectively – to determine the effect of surfactants on the size and distribution of Cu nanoparticles and on resulting CO2RR performance in acid electrolyte. The results reveal that Cu nanoparticles on surfactant-treated carbon black show different product profiles and selectivity in acid using flow cell compared to Cu nanoparticles on non-treated carbon black. In addition, surfactant functionalization plays important roles in the size and uniform distribution of Cu nanoparticles and electrochemical surface area. Overall, surfactant treatment allows Cu nanoparticles to distribute uniformly on carbon black, and it enables tuning of the selectivity of multi-carbon CO2RR products based on surfactant composition.