The Electrochemical Conversion of CO2 into Value-Added Chemicals and Fuels to Defossilize Society

The electrochemical conversion of CO² into value-added chemicals and fuels has gained significant interest in the scientific community over the past decades as a potential technology to help defossilize society. Several catalysts have been found to perform the selective conversion of CO² into different products, where Ag and Au can make CO, Sn and In can make formic acid/formate, and Cu can uniquely make up to 18 different products, many of which are C2+.

While Cu can make many products, one main challenge is understanding the mechanisms to promote the formation of specific products while also being able to suppress the formation of unwanted products, most notably hydrogen. In situ, spectroelectrochemical techniques such as surface-enhanced infrared absorption spectroscopy (SEIRAS) can probe catalyst surfaces during electrolysis and reveal vibrational modes of reaction intermediates and near-surface electrolyte compositions.

Here, we use in situ SEIRAS to probe reaction intermediates on Cu electrocatalysts during CO² reduction as a function of applied potential and electrolyte composition and concentration. Specifically, we observe how reaction intermediates change in speciation and concentration while operating in electrolytes that contain divalent cations (Ca²⁺, Mg²⁺), which are found both in tap water and seawater. We show that the divalent cations change the surface speciation and thus reaction pathways of CO2 reduction on copper, which highlights the complexity of using non-purified electrolyte streams that may be easier to use, but more challenging to optimize, thus our goal of optimization. And eventual defossilization of the energy industry and removal of CO² to stop climate change.