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Scalable Synthesis of Carbon Supported Platinum Lanthanide and Rare Earth Alloys for Oxygen Reduction Claudie Roy, Brian Peter Knudsen, Christoffer Mølleskov Pedersen, Amado Andrés Velázquez Palenzuela, Leif Hojslet Christensen, Christian Danvad Damsgaard, Ifan Erfyl Lester Stephens, and Ib Chorkendorff ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b03972 • Publication Date (Web): 17 Jan 2018 Downloaded from http://pubs.acs.org on January 17, 2018
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ACS Catalysis
Scalable Synthesis of Carbon Supported Platinum Lanthanide and Rare Earth Alloys for Oxygen Reduction Claudie Roy,a Brian P. Knudsen,a Christoffer M. Pedersen,a,b Amado Velázquez-Palenzuela,a,b Leif H. Christensen,b Christian Danvad Damsgaard,c Ifan E. L. Stephens,a,d and Ib Chorkendorff,a* a
Surface Physics and Catalysis , Department of Physics, Technical University of Denmark, DK-
2800 Kgs. Lyngby, Denmark b
Center for Nano- and Micro technology, Danish Technological Institute (DTI), Gregersenvej,
DK-2630 Taastrup, Denmark c
Center for electron nanoscopy , Department of Physics, Technical University of Denmark, DK-
2800 Kgs. Lyngby, Denmark d
Department of Materials, Imperial College London, SW7-2AZ-UK London, United Kingdom
Keywords: synthesis, rare earths, platinum, alloy, oxygen reduction reaction, proton exchange membrane fuel cell, nanoparticles
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ABSTRACT Platinum rare earth alloys have proven both active and stable under accelerated stability tests in their bulk polycrystalline form. However, a scalable method for the synthesis of high surface area supported catalyst of these alloys has so far not been presented. Herein we discuss the thermodynamics relevant for the reduction conditions of the rare earths to form alloys with platinum. We show how, the tolerances for water and oxygen severely limits the synthesis parameters and how under certain conditions the thermal reduction of YCl3 with H2 is possible from 500 ˚C. From the insight gained, we synthesized a PtxY/C by modifying a Pt/C catalyst, and confirmed alloy formation by both x-ray diffraction and x-ray photoelectron spectroscopy measurements. These reveal crystalline intermetallic phases and the metallic state of yttrium. Without any optimisation to the method, the catalyst has an improved mass activity compared to the unmodified catalyst, proving the viability of the method. Initial work based on thermodynamic equilibrium calculations on reduction time show promise in controlling the phase formed by tuning the parameters of time, temperature and gas composition.
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ACS Catalysis
INTRODUCTION Proton exchange membrane fuel cells (PEMFCs) are amongst the most promising renewable energy technologies, capable of producing electricity through electrochemical reactions of hydrogen and oxygen fuels at near room temperature (
