Transition metal chalcogenides in the oxygen evolution reaction: Surface reconstruction and in situ/operando characterization

The global energy crisis and environmental concerns are driving the development of clean and efficient energy conversion technologies. Electrocatalytic water splitting has emerged as a promising carbon-neutral method for hydrogen production. However, the oxygen evolution reaction (OER), a critical half-reaction, suffers from slow kinetics due to its multi-step electron-transfer mechanism. Developing highly active electrocatalysts to reduce the overpotential of OER is therefore essential.

In a recent perspectives article published in Frontiers in Energy, Haihong Zhong from Hainan University and Nicolas Alonso-Vante from Shanghai Jiao Tong University review the role of transition metal chalcogenides (TMCs) as OER pre-catalysts, with a focus on surface reconstruction and the application of in situ/operando characterization techniques. The article discusses how TMCs, such as sulfides and selenides of Fe, Co, and Ni, undergo dynamic structural changes during OER, forming active oxyhydroxide phases.

The authors highlight that TMCs often function as pre-catalysts, undergoing surface reconstruction under OER conditions to form disordered or amorphous oxyhydroxides—the true active species. This reconstruction involves oxidation, anion exchange, and structural reorganization, which enhance electrocatalytic performance.  

Several studies using operando X-ray absorption spectroscopy (XAS) and Raman spectroscopy are cited to illustrate these transformations. For example, in Ni-Fe selenides, reconstruction leads to Ni-Fe-OOH active phases, while in CoSx, conversion to CoOOH or high-valent Co(IV) species is observed. The residual chalcogen species, such as sulfates or selenites, are also noted to enhance OER activity and stability, particularly in challenging environments like seawater electrolysis.

Advanced microscopy techniques, including in situ transmission electron microscopy (TEM), have visually captured phase transitions, such as the transformation of CoSx to CoOOH, revealing dynamic morphology changes and oxygen bubble-induced effects during OER.

The article emphasizes that operando characterization—conducted under actual working conditions—enables direct correlation between catalytic performance and structural evolution. Techniques such as XAS, Raman spectroscopy, and TEM provide real-time insights into oxidation states, local coordination, and phase changes. However, each method has inherent limitations in spatial or temporal resolution, and a multimodal approach is often necessary to fully understand the complex reconstruction processes.

This perspectives article underscores the importance of elucidating surface reconstruction mechanisms to guide the rational design of efficient and stable OER electrocatalysts. The full text is available at: https://journal.hep.com.cn/fie/EN/10.1007/s11708-025-1038-9.