Sun Wei, Tian Xinlong, Liao Jianjun, Deng Hui, Ma Chenglong, Ge Chengjun, Yang Ji, Huang Weiwei
Key Laboratory of Agro-Forestry Environmental Processes and Ecological Regulation of Hainan Province, College of Ecology and Environment, Hainan University, 58 Renmin Road, Haikou, Hainan 570228, P.R. China.
State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, 58 Renmin Road, Haikou, Hainan 570228, P.R. China.
ACS Appl Mater Interfaces. 2020 Jul 1;12(26):29414-29423. doi: 10.1021/acsami.0c08358. Epub 2020 Jun 16.
The proton exchange membrane (PEM) electrolyzer for hydrogen production has multiple advantages but is greatly restricted by expensive iridium and sluggish oxygen evolution reaction (OER) kinetics. The most promising way to reduce the precious metal loading is to design and develop highly active Ir-based catalysts. In this study, a versatile approach is reported to prepare a hybrid in the form of a catalyst-support structure (Fe-IrO@α-FeO, abbreviated Ir@Fe-MF) by utilizing the self-dissolving properties of Fe-MIL-101 under aqueous conditions. The formation of this hybrid is mainly due to the Ir and released Fe ions coprecipitated to assemble into Fe-IrO nanoparticles, and the Fe released from the inward collapse of the metal-organic framework (MOF) spontaneously forms α-FeO. The prepared Ir@Fe-MF-2 hybrid exhibits enhanced catalytic activity toward OER with a lower onset potential and Tafel slop, and only 260 mV overpotential is required to drive the current density to reach 10 mA cm. The performed characterizations clearly indicate that the IrO coordination structure is changed significantly by Fe incorporated into the IrO lattice. The performed X-ray adsorption spectra (XAS) provides evidence that Ir 5d orbital degeneracy is eliminated because of multiple orbitals being semi-occupied in the presence of Fe, which is mainly responsible for the enhancement of OER activity. These findings open an opportunity for the design and preparation of more efficient OER catalysts of transition metal oxides by utilization of the MOF materials. It should be highlighted that a long-term stability of this catalyst run at a high current density in acidic conditions still faces great challenges.
用于制氢的质子交换膜（PEM）电解槽具有多种优势，但受到昂贵铱和缓慢析氧反应（OER）动力学的极大限制。降低贵金属负载量最有前景的方法是设计和开发高活性的铱基催化剂。在本研究中，报道了一种通用方法，通过利用Fe-MIL-101在水性条件下的自溶解特性，制备催化剂-载体结构形式的杂化物（Fe-IrO@α-FeO，缩写为Ir@Fe-MF）。这种杂化物的形成主要是由于铱和释放的铁离子共沉淀组装成Fe-IrO纳米颗粒，并且从金属有机框架（MOF）向内坍塌释放的铁自发形成α-FeO。制备的Ir@Fe-MF-2杂化物对OER表现出增强的催化活性，具有较低的起始电位和塔菲尔斜率，驱动电流密度达到10 mA cm只需260 mV的过电位。所进行的表征清楚地表明，通过将铁掺入IrO晶格中，IrO的配位结构发生了显著变化。所进行的X射线吸收光谱（XAS）提供了证据，由于在铁存在下多个轨道被半占据，Ir 5d轨道简并性被消除，这主要是OER活性增强的原因。这些发现为利用MOF材料设计和制备更高效的过渡金属氧化物OER催化剂提供了机会。应该强调的是，这种催化剂在酸性条件下高电流密度下的长期稳定性仍然面临巨大挑战。
