Temperature Effects on the Surface CO Population during CO<sub>2</sub> Electroreduction over Copper
Victor D. Brandão, Hakhyeon Song, Anush Venkataraman, Yuval Fishler, Sukaran S. Arora, Saket Bhargava, Carlos Villa, Adam Holewinski, Sankar Nair, Marta C. Hatzell, Carsten Sievers
Abstract
High Resolution Image Download MS PowerPoint Slide In industrial implementations, CO 2 electrolyzers will likely operate at high temperatures due to heat transfer limitations, but the effects of temperature on surface reactions involved in CO 2 electroreduction remain elusive and heavily based on inference from product analysis. In this study, we used surface-enhanced infrared absorption spectroscopy (SEIRAS) to deconvolute temperature-dependent phenomena affecting the CO population on copper between 20 and 80 °C. We show that CO coverage and migration to defect sites increase between 20 and 45 °C and decrease between 45 and 80 °C, suggesting that increasing temperature favors a CO hydrogenation route to C 1 products over a CO coupling route to C 2+ products. C 1 and C 2+ product formation rates have 1.28 and 1.95 order dependence on the concentration of CO on defect sites, respectively, indicating that these are the active sites for product formation between 20 and 80 °C. Thus, increasing temperature has a direct effect on the CO conversion route to C 1 and C 2+ products beyond just controlling local CO 2 availability, mass transport, and elementary reaction rates. These findings provide a deeper understanding of the underlying reaction mechanism at elevated temperatures, which is a key step in rationalizing product distribution and in designing solutions for enhanced C 2+ production in CO 2 electrolyzers.