The development of efficient routes toward sustainable fuel sources by electrochemical reduction of CO2 is an important goal for catalysis research. While these processes usually occur in the presence of solvent, solvation effects in catalysis are largely not understood or even characterized. In this work, mass-selected clusters of silver anions with CO2 serve as a model system for reductive activation of CO2 by a catalyst in the presence of a well-controlled number of solvent molecules. Vibrational spectroscopy and electronic structure calculations are used to obtain molecular-level information on the interaction of solvent with the catalyst-CO2 complex and the effects of solvation on one-electron reductive activation of CO2. Charge transfer from the silver catalyst to CO2 increases with increasing cluster size. We observe the coexistence of catalyst-ligand complexes with CO2 monomer and dimer anions, indicating that CO2-based charge carriers can exist in the presence of a silver atom.