The Microenvironment Frontier for Electrochemical CO2 Conversion

low CO₂ solubility in aqueous conditions the delicate balance between the delivery of essential proton donors for CO₂RR versus the strong tendency to convert donated protons to H₂ via the competing hydrogen evolution reaction (HER) the delicate balance between reaction pathways toward multiple CO₂RR products dynamic changes in local pH, ion concentrations, hydrophobicity, and active sites in response to phenomena such as carbonate formation and restructuring of electrocatalysts Figure 1. Schematic overview of CO₂RR microenvironment effects. (a) Microenvironment impact on CO₂RR performance. (b) Microenvironment considerations: experimental conditions, electrocatalyst characteristics, and electrolyte characteristics. (c) Description of the activity and activity coefficient for CO₂, CO, and H₂O (or other proton donors). Activity is the lens through which to understand numerous phenomena within the CO₂RR microenvironment Figure 2. Schematic overview for macroscale, microscale, and nanoscale effects on planar (a–c) and porous (d–f) electrodes. First, the activity coefficient and concentration terms offer a helpful parameter space to compare the effects of various interventions and adjustments to the microenvironment that had previously been difficult to compare based on objective measures (Figure 1b). Second, this approach highlights the importance of improving our understanding of the relative contributions of three-phase (gas–liquid–solid) and larger area two-phase (liquid–solid) interfaces on CO₂RR, which has attracted recent attention. (12,13) Third, this understanding highlights the importance of developing new in situ and in operando analytical techniques to probe the local distributions of CO₂, CO, and H₂O under reaction conditions. Attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) has already shown promise for quantifying bound versus free water during CO₂RR. (13) What are strategies to extend recent fundamental developments on controlling water activity to improve CO₂RR performance at high current densities? How can we use the microenvironment to explore electrochemical strategies to simultaneously accomplish CO₂ capture and conversion? Based on the historical development of CO₂RR approaches, can we or should we adopt new materials for CO₂RR GDLs and ionomers (typically materials developed for other chemical transformations with different requirements) to specialize in CO₂RR’s requirements? In CO₂RR, what is the structure of the three-phase gas–liquid–solid and other interfaces under reaction conditions? Leveraging the microenvironment, how can CO₂ be used to make higher-value products or products that can integrate into the economy to achieve net negative CO₂ emissions? What can new CO₂RR systems look like? Moreover, can we reimagine our strategies to valorize CO₂? Are there advantages to performing CO₂RR electrochemistry at high temperatures or high pressures? To what extent can we leverage the enzymatic microenvironment of living systems to achieve electrochemical CO₂ conversion to high-value products beyond C₃₊? Andrew B. Wong is an Assistant Professor in the Department of Materials Science and Engineering at the National University of Singapore. Prior to his independent career, he was a postdoctoral researcher at Stanford University, where he was coadvised by Thomas Jaramillo and James Harris. He received his Ph.D. in Chemistry from UC Berkeley in 2016 under Peidong Yang and received his joint B.S.–M.S. degree in Chemistry at the University of Chicago in 2011. The A.B. Wong Group focuses on understanding and developing control of the microenvironment for electrochemical CO₂ conversion and exploring emerging strategies to valorize CO₂. A.B.W. would like to acknowledge startup funds from the National University of Singapore through the Presidential Young Professorship early career award (WBS: A-0009245-05-00). Ongoing efforts on bioelectrochemical CO₂ conversion are financially supported by the Competitive Research Programme of the National Research Foundation Singapore (NRF-CRP27-2021-0004). This article references 14 other publications. This article has not yet been cited by other publications.