Nanoporous high-entropy alloys with low Pt loadings for high-performance electrochemical oxygen reduction

Pt-based alloys have been widely used as high-performance electrocatalysts for the oxygen reduction reaction (ORR). These catalysts contained high Pt contents, typically 60–70 at.% or higher, since further decreasing Pt contents would significantly lower the desired electro-catalytic activity. High-entropy alloys (HEAs) with built-in stability through their low free-energy phases provided a promising route to prepare Pt-based alloy catalysts with less than 50 at.% Pt while maintaining high ORR activity and stability in various environments. In this work, we reported a top-down de-alloying synthetic method to controllably incorporate five immiscible metals in one nanoscale solid phase. By predetermining four elements (Al, Cu, Ni and Pt) and alternating the fifth element including Pd, V, Co, Mn, etc., a series of nanoporous HEAs (np-HEAs) with Pt content of ~20–30 at.% were obtained. Among these quinary alloys, the Al-Cu-Ni-Pt-Mn np-HEA exhibited the best ORR catalytic activity and electrochemical cycling durability, well exceeding the commercial Pt/C catalysts. We expected these nanostructured HEA would offer a new class of alloy catalysts in many electrochemical reactions.