The present study accomplishes the partial reduction of CO2 to carbon monoxide in a dielectric barrier discharge (DBD) reactor packed with g-C3N4 and TiO2 or ZnO mixed with g-C3N4. Typical results indicate that the ZnO + g-C3N4 packed reactor provides ~12% CO2 conversion at SIE of 4.8 J/mL, whereas DBD yields only ~7.5% conversion under the same experimental conditions. The best performance of the ZnO integrated system is due to the presence of more basic sites than those of the TiO2 packed system, which enables effective adsorption of acidic CO2 on its surface. The highest energy efficiency of 1.106 mmol/kJ is achieved with 5% ZnO + g-C3N4 at SIE of 4.8 J/mL, whereas DBD exhibits only 0.746 mmol/kJ under the same conditions. Notably, catalyst packing also enables the highest carbon balance of ~97%. © 2020 Elsevier Inc.