- The full article entitled “Spin crossover-driven diiron electrocatalyst boosts sustainable catalytic water oxidation” can now be found at the Nature Sustainability website at https://www.nature.com/articles/s41893-025-01571-3
- Authors: Ching-Wei Tung, Wei Zhang,* Tai Ying Lai, Jiali Wang, You-Chiuan Chu, Guan-Bo Wang, Chia-Shuo Hsu, Yen-Fa Liao, Nozomu Hiraoka, Hirofumi Ishii, Xiao Cheng Zeng*, and Hao Ming Chen*
In green hydrogen production, the anodic oxygen evolution reaction (OER) during water splitting is a key step for renewable energy applications. However, its sluggish kinetics and reliance on precious metals have long constrained technological development. To address this challenge, Professor Hao Ming Chen from the Department of Chemistry, in collaboration with a team at City University of Hong Kong, has designed a novel iron molecular catalyst. Through a spin-crossover mechanism, the mononuclear complex undergoes dimerization to form the active dinuclear species [Fe2(μ-O)(μ-OH)(L1)2], achieving outstanding water oxidation activity and remarkable stability. The molecular catalyst delivers a current density of 10 mA/cm2 at an overpotential of only 184 mV and demonstrates operational durability exceeding 1,000 hours, greatly surpassing the performance of most existing iron-based catalysts.
A key technological highlight of this study is the application of in situ high-energy resolution X-ray emission spectroscopy. For the first time, the team captured direct evidence of a dynamic spin-state transition in the iron center from low-spin (LS) to high-spin (HS). This spin-state crossover triggers spontaneous dimerization of the mononuclear complex, forming the active [Fe2(μ-O)(μ-OH)(L1)2] core. The process enhances covalency between the metal centers, promotes the formation of O–O bond-containing intermediates, and effectively resolves the long-standing stability challenge of molecular catalysts.
This research underscores the critical relationship between dynamic spin states and the valence electron structures of transition metals, representing a key advance toward the design of efficient and sustainable non-precious molecular catalysts. Moreover, the use of in situ high-energy resolution X-ray spectroscopy highlights its irreplaceable role in probing dynamic electronic configurations and bonding structure changes during catalysis, offering new perspectives for the future development of molecular catalysts and green hydrogen production.
