Understanding Limitations in Electrochemical Conversion to CO at Low CO<sub>2</sub> Concentrations
Danielle A. Henckel, Prantik Saha, Sunil Rajana, Carlos Baez‐Cotto, A. Taylor, Zengcai Liu, Michael G. Resch, Richard I. Masel, K.C. Neyerlin
Abstract
High Resolution Image Download MS PowerPoint Slide Low-temperature electrochemical CO 2 reduction has demonstrated high selectivity for CO when devices are operated with pure CO 2 streams. However, there is currently a dearth of knowledge for systems operating below 30% CO 2, a regime interesting for coupling electrochemical devices with CO 2 point sources. Here we examine the influence of ionomer chemistry and cell operating conditions on the CO selectivity at low CO 2 concentrations. Utilizing advanced electrochemical diagnostics, values for cathode catalyst layer ionic resistance and electrocatalyst capacitance as a function of relative humidity (RH) were extracted and correlated with selectivity and catalyst utilization. Staying above 20% CO 2 concentration with at least a 50% cathode RH resulted in >95% CO/H 2 selectivity regardless of the ionomer chemistry. At 10% CO 2, however, >95% CO/H 2 selectivity was only obtained at 95% RH under scenarios where the resulting electrode morphology enabled high catalyst utilization.