Dr. Lili Lu
Lead Research Scientist, Corporate Technology, Siemens Shanghai Center, China

Speech Title: Power to X, Employing Single Step Direct Electrocatalytic Reduction of CO₂ Toward CO and Hydrocarbons

Abstract: Storage or conversion possibilities are essential for large overcapacities of renewable power generation from solar and wind, due to their intermittency and the volatility of electricity. However, compared to fossil fuels, it will raise problems concerning economic feasibility due to their physical efficiency limitations. Power to x might be one of the solutions. Renewable electric energy can be transformed into storable chemical feedstocks or energy carriers via electrolysis, such as CO (mix with H₂ for syngas) or ethylene, where the chemical value exceeds by far its pure heating value. Meanwhile, gas diffusion electrode was introduced for the purpose of overcoming the mass transport limitation of CO₂, which brought multi-benefit for the electrolyzer performance. In our work, CO could be obtained with faradic efficiencies over 90% at current densities exceeding the industrial necessary level ups to 300 mA/cm² demonstrated for more than 1,200 hours with continuous operation, with a total energy efficiency approaching 50%. Two models were discussed regarding continuous operation of CO₂ to CO electrolyzer. Ethylene is more challenging due to the highly complex reduction process. Faradic efficiencies up to 57% for ethylene at current densities above 150 mA/cm² could be obtained. In many experiments we also observed formation of liquid products of ethanol, C1-C3 alcohols, carboxylates, and ketones. To the best of our knowledge, the here reported faradaic efficiencies for ethanol above 20% at current densities above 150mA/cm² are among the highest values so far reported in the literatures.

Acknowledgements: Supported by Siemens Corporate Technology and German Ministry for Education and Research