Advances and Challenges in High-temperature Electrochemical CO2 Conversion Technology

During the past century, CO2 emissions around the world have continue to grow at an astonishing rate. In recent years, with the proposal of the global goal of “carbon neutralization”, high-temperature CO2 electrolysis technology based on solid oxide electrolysis cell (SOEC) has ushered in a rapid development opportunity. SOECs operating at elevated temperatures can not only make full use of industrial waste heat but also convert CO2 into hydrocarbon fuels or high-value-added chemical products via electrochemical reactions. Currently, multiple countries around the world have deployed various high-temperature electrochemical CO2 conversion projects. In 2017, Haldor Topsøe A/S (Denmark) reported the world’s first commercial CO2 electrolysis system, which can produce CO gas through SOEC electrolysis of CO2, with a production capacity of up to 10 Nm3 CO2/h. In 2019, Sunfire GmbH (German) developed a high-temperature co-electrolysis demonstration system which can product syngas at 4 Nm3/h rate. In 2020, the University of Aarhus (Denmark) reported a CO2 methanation reactor based on SOEC, which can upgrade biogas to pipeline mass methane in a 10 Nm3/h experimental device. Compared to the high-temperature water electrolysis for hydrogen production, the scale of the high-temperature CO2 electrolysis device is relatively small. With the increasing demand for energy density and power density of CO2 conversion devices in various new application fields, further research and development is necessary to overcome the challenges of high cost and low durability in large-scale application and commercialization.