title: Small palladium islands embedded in palladium-tungsten bimetallic nanoparticles form catalytic hotspots for oxygen reduction.
abstract: The sluggish kinetics of the oxygen reduction reaction at the cathode side of proton exchange membrane fuel cells is one major technical challenge for realizing sustainable solutions for the transportation sector. Finding efficient yet cheap electrocatalysts to speed up this reaction therefore motivates researchers all over the world. Here we demonstrate an efficient synthesis of palladium-tungsten bimetallic nanoparticles supported on ordered mesoporous carbon. Despite a very low percentage of noble metal (palladium:tungsten=1:8), the hybrid catalyst material exhibits a performance equal to commercial 60% platinum/Vulcan for the oxygen reduction process. The high catalytic efficiency is explained by the formation of small palladium islands embedded at the surface of the palladium-tungsten bimetallic nanoparticles, generating catalytic hotspots. The palladium islands are ~1 nm in diameter, and contain 10-20 palladium atoms that are segregated at the surface. Our results may provide insight into the formation, stabilization and performance of bimetallic nanoparticles for catalytic reactions.
authors.affiliation: Department of Physics, Umeå University, Umeå S-90187, Sweden.
authors.forename: Guangzhi
authors.initials: G
authors.lastname: Hu
authors.affiliation: Division of Applied Surface Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg S-412 96, Sweden.
authors.forename: Florian
authors.initials: F
authors.lastname: Nitze
authors.affiliation: 1] Department of Physics, Umeå University, Umeå S-90187, Sweden [2] Department of Chemistry, Umeå University, Umeå S-90187, Sweden.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gracia-Espino
authors.affiliation: Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Physics, Umeå University, Umeå S-90187, Sweden.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Barzegar
authors.affiliation: Department of Physics, Umeå University, Umeå S-90187, Sweden.
authors.forename: Tiva
authors.initials: T
authors.lastname: Sharifi
authors.affiliation: Department of Physics, Umeå University, Umeå S-90187, Sweden.
authors.forename: Xueen
authors.initials: X
authors.lastname: Jia
authors.affiliation: Department of Chemistry, Umeå University, Umeå S-90187, Sweden.
authors.forename: Andrey
authors.initials: A
authors.lastname: Shchukarev
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Chuansheng
authors.initials: C
authors.lastname: Ma
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.affiliation: Department of Physics, Umeå University, Umeå S-90187, Sweden.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wågberg