Chemical design of oxygen electrodes for solid oxide electrochemical cells: A guide

Solid oxide fuel cell (SOFC) and electrolysis cell (SOEC) technologies due to their potential hydrogen and low-carbon energy coincide with an intensive development trajectory for realizing transition to alternative energy policies. Energy conversion processes utilizing such devices include conventional (hydrogen utilization, water electrolysis) tactics, as well as novel approaches, such as CO2-electrolysis, non-oxidative hydrocarbon conversion, ammonia synthesis, etc. This variety of processes is supported by unique combinations of electrolytes with electrodes, which have different properties of catalytic and electrocatalytic activity towards electrochemical oxidation and reduction. To develop high-performance low- and intermediate-temperature SOFCs and SOECs, significant efforts should be focused on overcoming the limitations of oxygen (air/steam) electrodes associated with low oxygen reduction reaction kinetics. In this review, we highlight the most promising structural and chemical strategies to improve the electrochemical performance of oxygen electrodes at reduced operating temperatures. From the viewpoint of the structural strategy, the properties of simple perovskite structures and their layered derivatives are considered; from the viewpoint of the chemical strategy, different modifications of basic complex oxides are briefly discussed. These strategies allow the researchers to analyze the existing chemical engineering facilities and to select more efficient ways for designing modernized compositions of oxygen electrodes.