The morphology, crystal structure and oxygen evolution reaction electrocatalysis performance of scandium-doped MIL-101(Fe)

The oxygen evolution reaction (OER) electrocatalyst is highly desirable as it plays an important role in many energy conversion technologies by effectively reducing the OER process overpotential. Herein, the morphology, crystal structure and more importantly, the OER electrochemical activity of Scandium-doped MIL-101(Fe) were investigated. It was found that the competitive nucleation as well as the difference in the oxytropism between Sc³⁺ and Fe³⁺ ions, which lead to the crystalline structure change and consequently the morphology evolved from quadrangular star-shaped bipyramid to hexagonal bipyramids. Moreover, the OER electrocatalysis performance was improved significantly when incorporation Sc³⁺ ion into the MIL-101(Fe) host body. The X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the strong bimetal interaction between Fe³⁺ and Sc³⁺ ions, leading to well-modified Fe³⁺ electronic structure. It yielded optimal hydroxyl adsorption energy on Fe³⁺ and thus facilitated the process of O₂ evolution. Such Sc³⁺ ion doping strategy to modulate the OER performance was also extendable to other Metal-organic frameworks (MOFs) structures. It demonstrates a better OER activity with a low overpotential of 300 ​mV at 10.0 ​mA ​cm⁻² and Tafel slope of 125 ​mV dec⁻¹ for Sc-CoBDC-3, which provides great potential for fabricating optimal OER MOFs.