Indeed, many catalysts experience direct electrochemical competition for reactant CO2. For instance, formic acid (HCOOH) forms competitively with CO on Cu, Pd, and Ag, and such direct competition for CO2 impacts the apparent Tafel slopes for these products. As shown in Figure and discussed in greater detail in the Section S7 of the SI, the occurrence of competing HCOOH formation dramatically increases the apparent CO Tafel slope beyond its intrinsic value.