Building bridges in CO2 conversion: from mechanistic insights to advanced electrochemical devices

The push toward a circular economy and a lower carbon footprint is accelerating the search for energy technologies in which industrial CO₂ becomes a feedstock. Carbon dioxide electroreduction (CO₂RR) can close the carbon cycle by converting CO₂ into fuels and value-added chemicals while storing renewable electricity in chemical bonds, yet large-scale deployment is still limited by selectivity, stability, and energy efficiency. This thesis addresses these barriers through a progressive strategy that connects mechanistic insights to device engineering. First, silver and copper oxides are used as benchmark catalysts to clarify how the reaction environment governs the competition between CO₂RR and the hydrogen evolution reaction (HER). In gas-diffusion electrodes (GDEs), hydrophobicity and ionomer chemistry are shown to control local transport and interfacial properties, thereby shaping product distribution and durability. In situ Raman spectroscopy is employed to track structural and interfacial changes under operating conditions. Building on this understanding, a CeO₂@oxCNH hybrid catalyst is developed, combining improved conductivity with a mesoporous texture that enhances mass transport. Integrated into GDE architectures, this material delivers high operational stability, suppresses parasitic H₂ evolution, and broadens the product spectrum toward C₂ compounds. Finally, the work extends to a photoelectrochemical (PEC) flow-cell platform where Ti-doped hematite photoanodes are coupled with GDE cathodes. Illumination partially offsets the external bias, while the flow-cell architecture ensures efficient CO₂ delivery. This approach targets two system bottlenecks, slow oxygen evolution kinetics and limited CO₂ solubility, and reveals that performance does not scale linearly with the anode-to-cathode area ratio, underscoring the need to balance coupled reactions. Overall, the thesis shows that scalable CO₂RR requires synergy between catalyst design, interfacial engineering, and integrated device architectures for solar-assisted artificial photosynthesis.