properties could be achieved for their use in a variety of important applications, such as wastewater remediation, [4][5][6][7][8] catalysis, [9,10] energy storage, [11] and fuel cells. [12] Recently, a similar design principle was proposed by metallurgists to enhance the chemical complexity of alloys through the synthesis of multi-principal element alloys, also known as high entropy alloys (HEAs), [13,14] for enhanced mechanical properties. [13,15,16] In addition, some HEAs also show promising functional properties, such as super-paramagneticity and superconductivity. [17,18] Interestingly, it is noteworthy that most HEAs reported so far contain active transition metals, [19] such as Ni, Co, and Fe, which are commonly used for electrochemical catalysis; however, to our best knowledge, the research on HEAs for electrocatalysis is still rare.In the broad field of clean energy, it is critical to promote oxidation reaction and O 2 production in the state-of-the-art energy storage devices, such as fuel cells and metal oxygen batteries. However, the kinetics of such reactions, which is of a multistep process, [19] is usually sluggish; therefore, high performance electrochemically catalytic materials are in great need today to improve the efficiency of oxygen evolution Designing active, stable, yet low cost electrocatalysts for the oxygen evolution reaction (OER) is pivotal to the next generation energy storage technology. However, conventional OER catalysts are of low electrochemical efficiency while the state-of-the-art nanoparticle-based catalysts require mechanical supports, thereby limiting their wide deployment. Here, it is demonstrated that, due to the excellent corrosion resistance of the Fe-Co-Ni-Cr-Nb high entropy intermetallic Laves phase, fabricating a high entropy bulk porous nanostructure is possible by dealloying the corresponding eutectic alloy precursor. As a result, a core-shell nanostructure with amorphous high entropy oxide ultrathin films wrapped around the nanosized intermetallic ligaments is obtained, which together, exhibits an extraordinarily large active surface area, fast dynamics, and superb long-term durability, outperforming the existing alloy-and ceramic-based OER electrocatalysts. The outcome of the research suggests that the paradigm of "high entropy" design can be used to develop high performance catalytic materials.
