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Page 8 of 27 Chen et al. Energy Mater. 2025, 5, 500045 https://dx.doi.org/10.20517/energymater.2024.144

material exhibited excellent performance in co-electrolysis of H O/CO , establishing it as an ideal candidate
2
2
[45]
for the SOEC cathode .
Overall, perovskites have attracted considerable attention due to their excellent mixed ion-electron
conductivity and carbon-resistant properties. However, their conductivity is not as optimal as that of cermet
cathodes. Although cermet materials have higher electronic conductivity and catalytic activity, they have
problems such as easy migration and oxidation of metal elements at high temperatures. The development of
more stable cathode materials remains a pivotal objective within the current research landscape.
Furthermore, the study of the hydrogen electrode reaction mechanism and degradation mechanism is also a
very interesting topic. In-situ investigations employing a range of advanced characterization tools, including
transmission electron microscopy and X-ray photoelectron spectroscopy, when combined with first-
principle calculations and model simulations, will facilitate the elucidation of the SOEC cathode reaction
mechanism, and then find a way to improve the electrochemical performance of the cathode material. In
order to visualize the electrochemical properties of different perovskite cathode materials, the performance
differences between them are given in Table 3.

ANODE
Oxygen evolution reaction (OER) occurs at anodes of SOECs. Consequently, the anodes must exhibit high
electronic conductivity, ionic conductivity, catalytic activity, appropriate redox activity, and a matched
thermal expansion coefficient with electrolytes. The reaction typically involves the diffusion of oxygen; it is
necessary for anode to have a porous microstructure. Nevertheless, the issue of electrode and electrolyte
delamination during prolonged operation represents the most significant obstacle to the advancement of
SOEC anodes. To enhance stability, current research is mainly focused on the development of advanced
[63]
materials and microstructures and the optimization of existing techniques .

Materials design
La Sr MnO (LSM) has high catalytic activity and electronic conductivity, along with a matched
x
3-δ
1-x
coefficient of thermal expansion and favorable chemical compatibility with YSZ electrolyte materials . It
[64]
has been demonstrated that LSM will form a localized region of elevated oxygen partial pressure during
long-term operation. This will result in delamination with the electrolyte interface, thereby increasing the
resistance of the electrode and potentially leading to a decay of the performance of SOEC or even its
failure . Su et al. employed the spin-coating method to create a porous layer of YSZ between the LSM and
[65]
[66]
the electrolyte [Figure 5A] . It was found that the introduction of the YSZ porous layer accelerated the
diffusion of oxygen ions at the solid-solid two-phase interface (SSTPI), which led to a reduction in the
oxygen partial pressure in the SSTPI zone and inhibited the degradation of the anode. Furthermore, the
TPB area was increased, thereby improving the performance of SOECs. The reversible cycle operation
serves to decelerate the kinetic rate of the OER at the anode.

The doping of A-site rare earth or alkaline-earth metal ions is another common method for increasing the
concentration of oxygen vacancies, which is used to enhance the performance of anodes. As shown in
Figure 5B and C, the introduction of Au nanoparticles onto LSM-YSZ by impregnation can accelerate the
electron transfer rate and the formation of new TPBs during the reaction, thereby enhancing the stability of
[67]
the anode in an atmosphere with a higher oxygen partial pressure . Mahata et al. prepared LSCM with Sr
substituted by Ca by combustion synthesis and found that the electronic conductivity of the final product
[68]
varies with the Ca content . When Sr was completely replaced by Ca, the electronic conductivity of LCM
increased with the Ca percentage; while Sr was partially replaced, the conductivity decreased with the
increasing Ca percentage. As illustrated in Figure 5D, the hydrogen production of LCM is markedly higher
than pure LSM and partially Ca-doped LSCM. Furthermore, the hydrogen production does not decrease