Zhao Xin, Wang Shixun, Cao Yanhui, Li Yun, Portniagin Arsenii S, Tang Bing, Liu Qi, Kasák Peter, Zhao Tianshuo, Zheng Xuerong, Deng Yida, Rogach Andrey L
Department of Materials Science and Engineering, and Center for Functional Photonics (CFP), City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, P. R. China.
School of Materials Science and Engineering, Tianjin University, Tianjin, 300072, P. R. China.
Adv Sci (Weinh). 2024 Dec;11(47):e2405936. doi: 10.1002/advs.202405936. Epub 2024 Oct 30.
Electrocatalysts based on metal-organic frameworks (MOFs) attracted significant attention for water splitting, while the transition between MOFs and metal oxyhydroxide poses a great challenge in identifying authentic active sites and long-term stability. Herein, we employ on-purpose defect engineering to create high-density atomic level defects on two-dimensional Fe-MOFs. The coordination number of Fe changes from 6 to 4.46, and over 28% of unsaturated Fe sites are formed in the optimized Fe-MOF. In situ characterizations of the most optimized Fe-MOF electrocatalyst during the oxygen evolution reaction (OER) process using Fourier transform infrared and Raman spectroscopy have revealed that some Fe unsaturated sites become oxidized with a concomitant dissociation of water molecules, causing generation of the crucial *OH intermediates and Fe oxyhydroxide. Moreover, the presence of Fe oxyhydroxide is compatible with the Volmer and Heyrovsky steps during the hydrogen evolution reaction (HER) process, which lower its energy barrier and accelerate the kinetics. As a result, the optimized Fe-MOF electrodes delivered remarkable OER (259 mV at 10 mA cm) and HER (36 mV at 10 mA cm) performance. Our study offers comprehensive understanding of the effect of phase transformation on the electrocatalytic process of MOF-based materials.
基于金属有机框架（MOF）的电催化剂在水分解方面引起了广泛关注，然而，MOF与金属羟基氧化物之间的转变在确定真正的活性位点和长期稳定性方面带来了巨大挑战。在此，我们采用有针对性的缺陷工程在二维铁基MOF上创建高密度原子级缺陷。铁的配位数从6变为4.46，在优化后的铁基MOF中形成了超过28%的不饱和铁位点。使用傅里叶变换红外光谱和拉曼光谱对最优化的铁基MOF电催化剂在析氧反应（OER）过程中的原位表征表明，一些铁不饱和位点被氧化，同时水分子解离，导致关键的*OH中间体和铁羟基氧化物的生成。此外，铁羟基氧化物的存在与析氢反应（HER）过程中的Volmer和Heyrovsky步骤相兼容，这降低了其能垒并加速了反应动力学。结果，优化后的铁基MOF电极展现出卓越的析氧性能（在10 mA cm时为259 mV）和析氢性能（在10 mA cm时为36 mV）。我们的研究全面理解了相变对基于MOF材料电催化过程的影响。
