Bismuth-based materials can efficiently electrocatalyze the 2e–/2H+ reduction of CO2 to either CO or HCO2H depending on the composition of the electrolyte solution. For example, while electrodeposited bismuth materials promote the electrocatalytic reduction of CO2 to CO with fast kinetics (jCO ~5–25 mA/cm2) and high efficiencies (FECO ~90 %) in the presence of imidazolium ([Im]+) based electrolytes, an orthogonal chemistry is observed in the presence of [DBU–H]+ based salts. Electrolysis of CO2 with Bi/[DBU–H]+ promotes the reduction of CO2 to yield HCO2H, with selectivities as high as FEFA ~ 80% at jFA ~ 20–50 mA/cm2. We have undertaken a multipronged study to understand how different electrolyte cations influence reaction dynamics at the Bi/electrolyte interface and ultimately control the outcome of CO2RR. A combination of spectroscopic, electroanalytical and computational methods has been used to interrogate the dynamics between electrocatalyst, electrolyte and CO2 at the Bi/electrolyte interface and provide insight into the pathway(s) by which these systems activate CO2. These experiments show that both structural (e.g., size and shape) and electronic details (e.g., pKa, and aromaticity) of the electrolyte cations are important criteria that dictate the pathway(s) by which CO2RR proceeds. We will discuss the catalytic plasticity that is displayed by Bi/[electrolyte]+ systems, along with implications for future development of tunable catalyst/electrolyte combinations that can efficiently promote CO2 conversion.

How do interactions between protic cations and polarized bismuth cathodes control the pathway of CO2 reduction?

2019 Fall National Meeting

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