The catalytic reduction of CO₂/CO is key to reducing the 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 gas, aqueous solution, and aprotic solution. We demonstrate that the binding energy serves as a good descriptor for the gaseous and aqueous phases and allows catalysts to be categorized by reduction products. The CO^* vs O^* and CO^* vs H^* binding energies for these phases give 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.