The catalytic reduction of CO2/CO is key to reducing carbon footprint and producing the chemical building blocks needed for society. In this work, we performed a theoretical investigation of the differences and similarities of the CO2/CO catalytic reduction reactions in the gas, aqueous solution, and aprotic solution. We demonstrate that binding energy serves as a good descriptor for gaseous and aqueous phases and allows categorizing catalysts by reduction products. The CO vs. O and CO vs. H binding energies for these phases gives a convenient mapping of catalysts regarding their main product for the CO2/CO reduction reactions. However, for the aprotic phase, descriptors alone are insufficient for the mapping. We show that a microkinetic model (including the CO and H binding energies) allows spanning and interpreting the reaction space for the aprotic phase.