The catalyst was fixed in place by packing between the inner stainless-steel electrode and the quartz wall of the dielectric (15.7 mm outer diameter and 3.1 mm thick respectively). The discharge gap was fixed at 6.2 mm between the interior electrode and dielectric barrier, both of which were cleaned and polished between samples. An AC signal (12-20 kV, 19 kHz) was provided between the interior and exterior electrodes by an AC transformer (Allanson SS1235OX) and the input power provided to the transformer (denoted input power) was monitored by an input power meter. The plasma input power could be set using a variable autotransformer for each experiment to study the influence of plasma input power on CO2 The raw CO2 conversion yield, XCO2 (Equation ), was quantified by comparison to a measured calibration curve and used as the metric for catalytic activity. CO and O2 retention times were calibrated via a commercial calibration standard. Prior to each plasma catalysis experiment, null runs were performed with the catalyst in place but without the plasma to establish the baseline quantity of CO2 in the GC measurements (denoted CO2,in). The plasma input power was then set to a determined value during each experiment and the output gas of the reactor was sampled to measure the amount of unreacted CO2 in the exit stream (CO2,out). The raw CO2 conversion ratio, XCO2, was determined by the relative loss of CO2 during the experiment after accounting for the gas expansion for this isobaric reaction. The details of this correction are shown in the Supporting Information (Equations S1-4). This process was repeated three times on previously unused samples for each combination of catalyst material and reactor input power. The specific energy input (SEI) into the feedstock was defined by Equation S3, with the energy input varying by no more than 3% throughout the period of a single test. Each test consisted of a two-minute plasma-on period followed by a twenty-minute plasma-off and purge period. The isobariccorrected CO2 conversion percent values, (𝑓 !" ! ), and the SEI were utilized to determine the input power conversion of the process as in Equation S4. The gas residence time in the discharge region was assumed to be the same for all packed reactor conditions due to the highly uniform nature of the catalyst/support pair and the consistent sample-to-sample packing density.