A Molecular Assembly Promotes Reactivity of Cobalt Redox Intermediates in Electrochemical Oxygen Evolution

Xiaoyue Duan¹, Daopeng Sheng², Peng Zhu³, Ye Zhou¹, Xiang Huang⁴（黄祥）*, Pierre-Yves OLU⁵, Jiong Wang^1,6（王炯）*

¹Innovation Center for Chemical Science College of Chemistry Chemical Engineering and Materials Science Soochow University Suzhou 215006, P. R. China

²State Key Laboratory of Radiation Medicine and Protection School for Radiological and Interdisciplinary Sciences (RAD-X) Soochow University

³School of Chemical Engineering Zhengzhou University Zhengzhou 450001, P. R. China

⁴Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong)Shenzhen 518045, P. R. China

⁵John Cockerill Hydrogen Seraing 4100, Belgium

⁶Jiangsu Key Laboratory of Advanced Negative Carbon TechnologiesSoochow University Suzhou 215123, P. R. China

Adv. Funct. Mater. 2025, 35, 2509426

Abstract: To optimize the intrinsic activities of catalytic sites at high surface density is crucial for advancing heterogeneous molecular electrocatalysis. However, it remains elusive due to a lack of an appropriate heterogenization strategy in the catalyst design using ubiquitous graphitic supports. Herein, oxidized molybdenum disulfide nanodots (MoSO_x-d) with abundant sulfates edges are identified as efficient linkers to molecular Co-2, 2′-bipyridine (Co(py)₂) complexes, enabling a relatively high surface density of heterogenous Co sites. The sulfates tuned the Co sites from first to second spheres by forming a CoO₂S coordination linkage, which resulted in a moderately reactive HO-Co³⁺-OH intermediate in a Co²⁺, Co³⁺ to Co⁴⁺ redox-mediated pathway for oxygen evolution. This improved the intrinsic turnover frequencies (TOFs) of Co sites compared to ones grafted on common graphitic supports, as well as pristine molybdenum disulfide. A relatively low overpotential (η) of 314 mV is achieved at a current density of 10 mV cm⁻². These results establish a straightforward bottom-up strategy for constructing molecularly well-defined and surface-dense active sites for high-performance electrocatalysis.

Article information: https://doi.org/10.1002/adfm.202509426