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Page 2 of 27 Chen et al. Energy Mater. 2025, 5, 500045 https://dx.doi.org/10.20517/energymater.2024.144

hydrogen production technology is mainly based on the reforming and partial oxidation of fossil fuels,
which not only consumes a large amount of energy but also produces a lot of carbon dioxide. Therefore, the
development of clean and efficient hydrogen production technology has become a hot research topic today.
As shown in Figure 1, strategies are being implemented worldwide to build a renewable energy economy
and infrastructure .
[2]
Solid oxide electrolytic cells (SOECs) are highly efficient electrolysis devices that convert water into
hydrogen and oxygen through electrolysis. Compared with traditional low-temperature electrolysis
technology, SOECs have higher energy efficiency and faster reaction rate, and show great potential in
hydrogen production. However, the early experimental work usually focused on the synthesis and
performance study of high-temperature solid oxide electrolytes. In recent years, with the worsening energy
crisis and increasing environmental awareness, solid oxide electrolysis technology has received growing
attention. Researchers have continuously improved the properties of solid oxide electrolytes, such as ionic
conductivity, chemical stability and mechanical strength, by optimizing the material composition,
microstructure and preparation process.

At present, solid oxide electrolysis cells (SOECs) play an important role in energy conversion, storage and
utilization due to a number of advantages such as high-efficiency conversion, high-temperature operation
and high-purity gas output. As most clean electricity is intermittent and variable and cannot be directly
connected to the grid, SOECs can be used to convert electrical energy into chemical energy for long-term
energy storage. Depending on the feed gas, SOECs can produce various products. H can be produced by
2
electrolysis of water, enabling large-scale production of “green hydrogen”. Compared with the conventional
alkaline electrolysis, anion exchange membrane (AEM) and proton exchange membrane (PEM) hydrogen
production technologies, SOECs are highly efficient, cost-effective and environmentally friendly. SOECs can
also be used for the co-electrolysis of H O and CO to produce H , CO and other chemical products .
[3]
2
2
2
Reversible solid oxide cells (RSOCs), which combine the advantages of both SOEC and solid oxide fuel cell
(SOFC) models, play an important role in the carbon neutrality goal, as they enable carbon recycling in
addition to promoting the efficient use of renewable energy sources and the production of “green
hydrogen” . RSOCs offer an efficient and sustainable solution to China's carbon neutrality goals and will
[4]
play an important role in the world's energy system. Table 1 shows the performance of different electrolysis
technologies.
The higher temperatures required for SOEC systems reduce the demands on reaction kinetics, helping to
overcome some limitations of conventional electrolysis cells. This results in increased electrolysis efficiency
and reduced polarization losses. However, SOEC systems also face numerous challenges, including the
disruption of material structure at high temperatures, expansion and contraction due to mismatched
thermal expansion between the electrode material and other components during redox cycling, and the
potential adverse effects of gases and other products generated during electrolysis on the electrode
[6]
material .
WORKING PRINCIPLE OF SOEC
Basic chemical reactions
SOECs are highly efficient electrochemical devices based on the conduction of oxygen ions or protons in
solid oxide electrolytes. A SOEC consists essentially of a cathode (fuel electrode), an anode (air electrode)
and a porous dense electrolyte (ion conductor) [Figure 2]. For a SOEC with oxygen ions conducting
electrolyte, at high temperatures (typically between 600 and 1,000 °C), steam accepts electrons at the
cathode and is reduced to form H and O . At the same time, oxygen ions pass through a dense electrolyte
2-
2