Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3δ.pdfVIP

SOSI-14218; No of Pages 10 ARTICLE IN PRESS Solid State Ionics xxx (2017) xxx–xxx Contents lists available at ScienceDirect Solid State Ionics journal homepage: /locate/ssi Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3?d Shay Robinsona,*, Christian Kj?lsethb, Truls Norbya aCentre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, FERMiO, Gaustadaléen 21, NO-0349 Oslo, Norway bCoorsTek Membrane Sciences AS, Gaustadaléen 21, NO-0349 Oslo, Norway ARTICLE INFO Article history: Received 21 November 2016 Received in revised form 13 February 2017 Accepted 16 February 2017 Available online xxxx Keywords: Point-contact electrode Hydrogen oxidation Platinum Copper Proton ceramic ABSTRACT The hydrogen oxidation kinetics of Cu and Pt point contact-electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3?d (BZCY72) were studied over a range of temperatures and hydrogen pressures using impedance spectroscopy. Characteristic capacitances were used to identify process contributions as charge and mass transfer, then Langmuir adsorption theory and Butler-Volmer charge transfer formalism were used to propose a hydrogen oxidation model to describe the experimental data. The charge transfer hydrogen pressure dependencies were pH32/4 for Cu, attributed to a high occupancy of adsorbed oxygen at three-phase boundary sites in the water-vapor containing atmosphere, and pH2?1/4 for Pt, corresponding to a hydrogen saturated interface. The Cu and Pt point contact electrodes exhibit similar temperature dependencies for charge transfer, with activation enthalpies of 0.82 and 0.93 eV, and pre-exponentials of approximately 160 and 1000 Y?1cm?1, respectively. Mass transfer dominated the total polarization resistance of both metal point contact electrodes, exhibiting a pH12/2 hydrogen pressure dependency. The activation enthalpies are 1.21 eV for Cu and 0.73 eV for Pt, re?ecting the higher catalytic activity generally expected f