The electrochemical CO₂ reduction reaction converts CO₂ and electricity into fuels and chemical feedstocks. The products can vary from CO and formate to ethylene and alcohols depending on the catalyst used in the cell. In this study, we present a temperature-controlled microflow cell and study the role of catalyst on CO₂ reduction. The standard laboratory configuration of the cell and the low solubility of CO₂ in aqueous electrolyte limits current densities to a few tens of mA cm⁻². Gas-diffusion electrodes in microflow cells supply CO₂ from the gas phase and reach much higher currents, but make the catalyst layer, the membrane and the gas–liquid interface integral part of the measurement. Temperature changes CO₂ solubility, ion transport and the barriers of competing pathways, so a single-temperature experiment cannot separate these contributions. Our microflow cell setup is built to probe catalysts from 30 to 70 °C with online gas chromatography quantifying H₂, CO and C₂H₄ at each temperature step. For Ag-promoted CuO/ZnO electrodes, lowering the catalyst loading raises the carbon-product partial current density, while the H₂ partial current density and the C₂H₄/CO ratio stay unchanged. Because hydrogen evolution is not transport-limited, this points to CO₂ supply rather than active area as the limiting factor for carbon products.