Layered double hydroxides for oxygen evolution reactions

To guide the design and synthesis of electrocatalysts towards highly efficient oxygen evolution reactions (OER), researchers from Beijing University of Chemical Technology summarized four common strategies to improve the OER performance of layered double hydroxides (LDHs) as well as identify active positions for LDHs.

They published their work on September 7 at Advances in Energetic Materials.

“With the increasing demand and consumption of fossil fuels, energy shortages and environmental pollution are becoming serious and indifferent,” said corresponding author Mingfei Shao, a professor at the State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing. “It is necessary to explore sustainable and renewable energy. Hydrogen, especially, is a new energy with great application prospects.”

The production of high-purity hydrogen can be achieved by electrochemical water splitting using electricity transformed from renewable energy sources such as wind and solar energy. But as one of the half-reactions, OER is a four-electron, low-energy process, according to Shao.

Shao and his team are focusing on LDHs, a large type of two-dimensional material. The broad coordination potential, molar ratios and intermediate anions, make it an excellent catalyst for OER in alkaline media.

“We summarized four common strategies applied to improve the OER efficiency of LDHs. Through these strategies, the overpotential of OER can be reduced, leading to high energy utilization efficiency,” Shao said. “Some works on the identification of active sites for LDH are introduced. The revelation of the reaction mechanism and active sites provide the theoretical guidance for the design of efficient electrocatalysts.”

The development and exploration of OER catalysts is currently mostly in the experimental stage, which cannot meet the standards for large-scale practical use. For example, there are still problems related to enlarging the size of catalysts and maintaining stability during OER. In addition, most reported methods for preparing LDH-based catalysts are complicated and time-consuming, which leads to high costs and limits their application, according to Shao.

“The identification of active oxygen species, such as oxygen species adsorbed by active sites on the surface of electrocatalysts and oxygen radical diffused into the solution during OER remains unclear due to the unstable and invisible existence of active oxygen species,” Shao said. “After identifying these reactive oxygen species, it is still crucial how to harness them for more efficient OER.”

“We hope that this review can provide insights into the further identification of active sites for LDHs in order to provide guidance for the design of more advanced electrocatalysts toward electrochemical water splitting,” Shao said.

Provided by Beijing Institute of Technology Press