Such catalysts, and intermetallic alloy catalysts as well 4, are perhaps the predominant pathway for making most of the state-of-the-art alloy catalysts. Noble metal phase-segregation, e.g., “Pt-skin” 3, 4, 8, 16, 17, by deliberate or unavoidable dealloying of the non-noble metals or deposition of the noble metals 18, is supported by high-resolution imaging and mapping of highly-limited and carefully-selected individual particles and theoretical considerations 4, 5, 8, 9. However, the high atomic percentage of PGMs for the state-of-the-art alloy catalysts and their poor activity and durability under fuel cell operating conditions constitute major barriers to fuel cell mass commercialization 15. Alloying noble metals with non-noble metals enhances the ORR activity while reducing the cost of catalysts 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. The mass commercialization of PEMFC, however, is hindered by high cost and poor performance of platinum group metal (PGM, e.g., Pt, Pd, etc.) catalysts for oxygen reduction reaction (ORR) taking place in the fuel cell’s cathode. Proton-exchange membrane fuel cells (PEMFC) represent a clean and sustainable energy conversion vector for transportation and stationary power generation 1, 2. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. However, under fuel cell operating conditions, state-of-the-art oxygen reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells.

Hr xps peak pd 3d