Nonmetal-Hybridized Interstitial High-Entropy Platinum Alloys for Oxygen Electrocatalysis in Practical Fuel Cells

Discovering catalysts with both extraordinary activity and stability is a pivotal, yet highly challenging task for many modern electrocatalysis. High-entropy alloys (HEAs) have been considered promising electrocatalysts that could fulfill both requirements, in that their high configurational entropy could stabilize the catalyst independently of the enthalpic factor closely coupled to catalytic efficacy. It is hypothesized that incorporation of nonmetallic elements (N, B, F etc.) into conventional all-metallic HEAs might stimulate unique virtues complementing the roles of metallic constitutes. However, incorporating multiple light nonmetal elements into HEAs within a single synthesis is highly challenging, where distinctive and harsh synthetic conditions are typically required, due to the vastly differing properties of these nonmetals and their low affinities to many late transition metals. Here we introduce a generic synthesis that can simultaneously incorporate B, N, F into the interstitial sites of Pt-based HEA, and propose nonmetal-hybridized interstitial HEAs as material-exploration platforms for efficiently discovering exceptional electrocatalysts. As a first example, we demonstrate that these interstitial Pt HEAs can act as outstanding oxygen reduction electrocatalysts for fuel cells, particularly the N-incorporated catalysts exhibiting the-state-of-the-art activity and durability at both material and membrane-electrode-assembly levels. Given the distinct properties of B and F to N, such as electronegativity and polar hydrophobicity, we anticipate that B-/F-/multi-nonmetal incorporation could lead to more advanced compositions and elaborately designed catalyst layers, facilitating the construction of a catalytically more effective and robust mass-transport networks for ultralow-Pt fuel cells. The concept of nonmetal-hybridized interstitial HEAs presents tremendous opportunities for addressing challenging electrocatalysis involving complex tandem reaction steps.