Electrocatalytic Upgrading of CO2 to Light Olefins in Protonic Ceramic Electrochemical Cells

Abstract

Light olefins (ethylene, propylene, butylene) are primary building blocks for chemical manufacturing of large volume products including organic chemicals, plastics, and even sustainable aviation fuels. Currently, the dominant commercial process for olefin production is steam cracking of naphtha or ethane, which is highly energy intensive and accounts for a large fraction of global CO2 emissions. To decarbonize olefin production processes, electrochemical CO2-to-olefin conversion coupled with renewable or low-emission energy sources including electricity and heat offers an attractive alternative. Previously, extensive research efforts have been devoted to low temperature electrochemical CO2 reduction in aqueous media, i.e., occurring below 100 °C. This approach, however, still faces enormous scientific and technological challenges in improving CO2 utilization, energy efficiency, and product selectivity. In this work, we have developed a new electrochemical process for direct conversion of CO2 to ethylene at intermediate temperatures (350-500°C) in an electrochemical membrane reactor. This process is based on high-performance protonic ceramic electrochemical cells (PCECs) that integrate CO2 hydrogenation reaction to produce olefins in the cathode and concurrent hydrogen generation reaction in the anode to provide hydrogen for CO2 conversion. Highly active and selective catalysts for CO2-to-olefin conversion have been identified and integrated into the PCECs. Both the catalytic and electrochemical performances of the integrated reactor system are evaluated and optimized. In contrast to the use of molecular H2 in conventional thermal catalytic pathways, the active hydrogen in PCECs could be sourced from different feedstocks including H2O, light alkanes, and ammonia, etc. This work also provides valuable insights into the selection and design of efficient catalysts for electrochemical CO2 conversion at elevated temperatures.