They published their work on Sep. 7 in Energy Material Advances.
"With the rising demand and consumption of fossil fuels, energy shortage and environmental pollution are becoming severe and unignorable," said the corresponding author Mingfei Shao, professor with the State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing. "It is necessary to explore sustainable and renewable energy, especially, hydrogen is a new energy with splendid application prospects."
Production of highly pure hydrogen can be achieved by electrochemical water splitting using the electricity transformed from renewable energy such as wind and solar energy. But as one of the half reactions, OER is a four-electron process, which causes a low efficiency of energy utilization, according to Shao.
Shao and his team focus on LDHs, a large kind of two-dimensional materials with wide tunability of the types, molar ratios of metal element and the nature of interlayer anions, are outstanding catalysts for OER in alkaline medias.
"We summarized four common strategies applied to improve the OER performance of LDHs. Through these strategies, the overpotential of OER can be decreased obviously, leading to a high efficiency of energy utilization," Shao said. "Some works about the identification of active sites for LDHs are introduced. Revelation of reaction mechanism and active sites provide the theoretical guidance to design efficient electrocatalysts."
Until now, the development and exploration of OER catalysts is mostly in the experimental stage at present, which cannot meet up the standards for large-scale practical use. For instance, problems are still remained to enlarge the size of catalysts and maintain the stability during OER with a severe condition, such as high alkalinity and high temperature. Besides, most reported preparation methods of LDHs based catalysts are complicated and time-consuming, which brings high cost and restricts their application as well as popularization, according to Shao.
"The recognition of reactive oxygen species such as oxygen species adsorbed by active sites on the surface of electrocatalysts and oxygen radical dispersed in the solution during OER still remains ambiguous due to the instable and unapparent existence of reactive oxygen species," Shao said. "After recognizing these reactive oxygen species, how to take advantage of them for more efficient OER is still vital."
"We hope this review can offer ideas to further identify the active sites for LDHs with the purpose of providing guidance to design more advanced electrocatalysts towards electrochemical water splitting." Shao said.
Other contributors include Xin Wan, Yingjie Song and Hua Zhou, all with the State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing.
The National Natural Science Foundation of China (22090031, 21922501 and 21871021), Project funded by China Postdoctoral Science Foundation (2021M690319) supported this work.
