Solid oxide cells (SOCs) are electrochemical energy converters that can operate in two different modes with high efficiencies. In fuel cell mode (solid oxide fuel cell, SOFC), they directly convert chemical energy from various fuels into electricity, which is the electrochemical reaction of oxygen ions and fuels forming H2O/CO2 (or reaction of a proton with oxygen forming H2O) in a controlled manner. The opposite reaction mode, the splitting of water into hydrogen and oxygen or reforming CO2 into CO and O2, is electrolysis (solid oxide electrolysis cell, SOEC). SOCs typically operate between 500°C - 900°C. These unit cells primarily consist of three components for the fundamental electrochemical reactions: an electrolyte as an oxygen/proton conductor and two electrodes- the anode and the cathode for gas reactions. Moreover, interconnectors, sealants, and current collectors are mainly required to assemble single cells into stacks for large electricity generation or hydrogen production.

Solid oxide cells represent a logical choice for electricity or hydrogen generation due to their high efficiency, modularity, fuel flexibility (SOFC), the capability of integrating heat and electricity from renewables and nuclear energy (SOEC), as well as being a grand energy storage option while operating under the reversible mode. SOC systems appear poised for commercialization, but widespread market acceptance/penetration will require continuous innovation of materials and system engineering to enhance unit performance and system lifetime and reduce cost. The development of novel materials for key components and operation strategies optimization in SOC with modeling pays attention to durable operations, especially with a deeper understanding of a variety of complicated physical, chemical, electrochemical, and mechanical processes occurring inside SOCs. Therefore, the section will summarize the recent development of SOCs, scoping from material to system, from experimental to modeling, and from performance improvement to degradation analysis/diagnosis. With the recent advances of SOCs, it is expected that the development of technology will be accelerated, and commercial implementation will be promoted.

This Research Topic will investigate materials/stack/system/operation/modeling for various applications. Subjects of interest may include, but are not limited to:

• Theory calculation, synthesis, and characterization of emerging electrode/electrolyte materials
• Interconnect/Sealant/Current collector development
• SOFC/SOEC system operation or optimization
• Proton electrolyte development or SOC operation based on proton electrolytes
• System, stack, or materials degradation analysis after long-term operation
• Reversible SOC system development, simulation, or operation.