IDEA, Nantes, France, -4 Noember 016 PN CERAMIC ELECTRDICS T. Norby, a R. Strandbakke, a E. Vøllestad, a Min Chen, a S.A. Robinson, a C. Kjølseth b a Uniersity of slo, Department of Chemistry, SMN, FERMi, Gaustadalléen 1, N-0349 slo, Norway B CoorsTek Membrane Sciences AS, Gaustadalléen 1, N-0349 slo, Norway PCE U 4 4e - 400-700 C ydration Redox electrode EIS: CT, MT SCL Mixed conduction Voltammetry
The electrolyte; example Y-doped BaZr 3 Doping reaction 3 Ba Y Y BaZr / x 3 Zr 5 ydration (g) x = Note: This is not an electrode ox reaction. The charge carriers do not enter ia an electrode reaction They are present in equilibrium with (g)
-side reaction Electrode ox reactions (g) e -side reaction (g) 4 4e (g) 4
Electrode reaction pathways
-side (g) int i, i i i,, (g) tpb,,, e,tpb/i,int,tpb/i,int Diffusion Diffusion CT
side (g) (g),tpb tpb,,, e,tpb,tpb,tpb Diffusion CT Diffusion
Charge transfer (CT),tpb/i,int,tpb/i,int e G eq ct, = n Fi 0, = ( n F) k 0 ct, Q Q β 1β react, prod, p - (and p?)- dependencies,tpb e,tpb,tpb G eq ct, ox = n ox Fi 0, ox = ( noxf) k 0 ct, ox Q Q βox 1β ox react, ox prod, ox p - and p - dependencies
Cu and Pt point electrodes on BZCY in S.A. Robinson, C. Kjølseth, T. Norby, Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr 0.7 Ce 0. Y 0.1 3d, in pub.
Cu and Pt point electrodes on BZCY in S.A. Robinson, C. Kjølseth, T. Norby, Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr 0.7 Ce 0. Y 0.1 3d, in pub.
Mass transfer (MT) Adsorption Dissociation Dissolution Diffusion G = eq mt (F) K 0 mt, p 1/, (4F) eq 0 n m Gmt, ox = Kmt, ox p p
Cu and Pt point electrodes on BZCY in G,tpb/i,int eq ct, = n,tpb/i,int e Fi 0, = ( n F) k 0 ct, Q Q β 1β react, prod, CT MT G = eq mt (F) K 0 mt, p 1/, S.A. Robinson, C. Kjølseth, T. Norby, Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr 0.7 Ce 0. Y 0.1 3d, in pub.
Electrode space charge layer (SCL) = F F u Fc dx x F u Fc G eq scl (0) exp (0) ) ( exp 0, ϕ λ ϕ ϕ λ
BGBSCLCT for nanograined Ni on BZY in Min Chen, T. Norby, Space Charge Layer Effect at the Ni/BaZr 0.9 Y 0.1 3-δ Electrode Interface in Proton Ceramic Electrochemical Cells, under publication
Mixed conduction example -side electrode Ideal conductor Model PCFC cathode Ideal conductor Ideal PCFC cathode Typical oxide conductor Typical PCFC cathode e - e - 4e - 4 4 4e - 4e - - - 4e - 4 4
PCFC oxygen electrodes (cathodes) Mixed conductiity: protons, oxide ions, electrons (holes) Typical oxide conductor Typical PCFC cathode e - e - 4e - - - 4e - 4 R. Strandbakke, V. Cherepano, A. Zue, D.S. Tsetko, C. Argirusis, G. Sourkouni-Argirusis, S. Prünte, T. Norby, Gd- and Pr-based double peroskite cobaltites as oxygen side electrodes for proton ceramic fuel cells and electrolyser cells, Solid State Ionics, 78 (015) 10.
Peroskite electrode on BaZr 0.7 Ce 0. Y 0.1 3 (BZCY) Impedance spectra yield apparent electrode polarisation resistances -1. -1.0-0.8 Electrolyte Electrode Z // (Ωcm ) -0.6-0.4-0. S0 S1 R p 1 R p S 0.0 14.0 14.5 15.0 Z / (Ωcm )
Peroskite electrode on BaZr 0.7 Ce 0. Y 0.1 3 (BZCY) but a more correct treatment is requi needs more input parameters and assumptions -1. -1.0-0.8 Electrolyte Electrode Z // (Ωcm ) -0.6-0.4-0. S0 R p 1 S1 R p S 0.0 14.0 14.5 15.0 Z / (Ωcm ) Recipe: Get indiidual R s from conductiity data Calibrate to R at S0 Calculate properly R R p,1 at S1 Calculate properly R R p,1 R p, at S Express and fit 4 unknown R p s to ariations in T, p, p
Peroskite electrode on BaZr 0.7 Ce 0. Y 0.1 3 (BZCY) Modelling by fitting all data Protons s oxide ions Effect of electronic conduction CT and MT(d) 1 T ( C) 700 600 500 400 10 log(r(ωcm )) 0-1 R p, - R p, R p,d, 1 0.1 R(Ωcm ) R p,ct, R p R p,app - 1.0 1. 1.4 1.6 0.01 1000/T (K -1 )
Voltammetry Tafel plot displays the kinetics of only the forward or backward reaction Yields β, n, i 0 May require EIS to deconolute R s and η s Example: Ni on BZY
Summary ydration (g) x = Redox-reactions (g) e Reaction paths and CT,tpb/i,int,tpb/i,int e EIS Separate into GGB, (SCL?), CT, MT Pre-exponential: Microstructure Actiation energy: Kinetics p, p, p dependencies: Mechanistics Mixed conduction D. Poetzsch, R. Merkle, J. Maier, J. Electrochem. Soc., 16 [9] (015) F939. Voltammetry
Acknowledgements The research leading to these results has receied funding from the European Union's Seenth Framework Programme (FP7/007-013) for the Fuel Cells and ydrogen Joint Technology Initiatie under grant agreement n 6144, and from the Research Council of Norway through the PN (5103), FXCET (8355), and RMA (19194) projects.