Mechanochemical synthesis of novel rutile-type high entropy fluorides for electrocatalysis

Multicomponent rutile (P4$_{2}$/mnm) structured fluorides, containing 4 to 7 transition metals (Co, Cu, Mg, Ni, Zn, Mn, and Fe) in equiatomic ratios, were synthesized using a simple mechanochemical approach. The high entropy fluorides were characterized using different techniques, all of which indicate that the high entropy fluorides tend to crystallize into a homogeneously mixed solid solution and single-phase structure. These high entropy fluorides represent an additional class of high entropy ceramics, which have recently attracted attention especially due to the development of high entropy oxides. With the introduction of these novel high entropy fluorides, similar interest could be generated due to the variety of different applications for fluoride materials and the improvements the high entropy concept might bring. Here we present an in-depth characterization study and the potential application of high entropy fluorides as a catalyst for the oxygen evolution reaction, in which the high entropy fluorides do show increased performance compared to a state-of-the-art catalyst for the oxygen evolution reaction, IrO$_{2}$, despite eliminating noble metal constituents.