PERFORMANCE OF Ni- ELECTRODEPOSITED GDC ANODES FOR SOLID OXIDE FUEL CELLS

Transcription

1 PERFORMANCE OF Ni- ELECTRODEPOSITED GDC ANODES FOR SOLID OXIDE FUEL CELLS Zadariana Jamil 1,2, Enrique Ruiz-Trejo 1, Paul Boldrin 1 and Nigel P Brandon 1 1 Imperial College London,UK 2 Faculty of Civil Engineering, Universiti Teknologi MARA Pahang

2 Introduction SOFC Operation O 2 (air) e - Fuel Ni e - TPB H 2 H 2 O H 2 H 2 O e - O 2- O 2- O 2- YSZ electrolyte O 2- Cathode Electrolyte Anode High ionic and electronic conductor; electrocatalytic active & large TPB

3 Anode Fabrication Methods Conventional - Electrocatalyst +ionic conductive ceramic >>sinter at high T Fabrication Methods Electroless and Electrodeposition Method Infiltration - Electrocatalyst ions are infiltrated into ionic conductive ceramic scaffold Disadvantages Difficult to obtain homogenous sample Not suitable for low melting point metals Time and energy consuming: requires multiple steps & high deposition temperature

4 Objectives To fabricate Ni/GDC electrodes by electroless Ag following Ni electrodeposition method. To measure the electrochemical performances of Ni-electrodeposited GDC electrodes. To determine the ability of the fabricated fuel cell operating in H 2 and syngas

5 Experimental Electroless and Electrodeposition of Ag and Ni

6 Electroless and Electrolytic Process for Anode Preparation 1300 o C, 1h Tollens reagent Screen printing GDC ink on 8YSZ Ready for testing Porous GDC scaffold Ag electroless into the GDC scaffold Ni 2+ aqueous solution (70 o C) Ni electrodeposit on Ag/GDC scaffold Ni electrodeposition Ag deposit on scaffold Total time: ~1 h, Low temperature

7 Deposits of Ag and Ni GDC virgin scaffold GDC scaffold with Ag Nielectrodeposited GDC scaffold

8 Log (conductivity) (S.cm -1 ) Electrical conductivity measurement Van der Pauw Method GDC Temperature ( o C) Ag Ag Ni Infiltrated Ni/GDC Inf-Ni/GDC Electro-Ni/GDC El-Ni/GDC Comb-synthesis-Ni/YSZ Comb-synthesis Ni/YSZ GDC Electrodeposited : 3.5 %vol-ni/ag/gdc Infiltration:11.6 % vol-ni/gdc (M. Lomberg et al., 2014) Combustion synthesis: 30 %vol-ni/ysz (U. A. Tamburini et al. 1998)

9 Electrochemical measurement

10 -Z'' ( cm 2 ) Symmetrical cell measurement in different %H Hz 97 vol % H 2 60 vol % H Hz 10 3 Hz vol % H 2 Ag/GDC Fitting Hz 0.1 Hz 0.1 Hz H 2 -N 2 Concentration (%) Z' ( cm 2 ) R_m (.cm 2 ) R_l (.cm 2 ) Total Electrode Polarization 10H 2-90N H 2-40N H 2-3H 2 O Ag/GDC 97H 2-3H 2 O

11 -Z'' ( cm 2 ) Symmetrical cell measurement at different T Temperature ( o C) R_m (.cm 2 ) R_l (.cm 2 ) Total Electrode Polarization o C 700 o C 650 o C 600 o C Fitting Hz 0.1 Hz Hz 0.1 Hz 10 Hz 10 Hz 10 2 Hz 10 2 Hz 10 2 Hz 10 3 Hz Hz Z' ( cm 2 ) Total ASR reported in the literature is in the range of Ω.cm 2. M. Lomberg et al., (2014). J. Electrochem. Soc. (161); R. Barfod et al., (2005) Fuel Cells (6).

12 log R (.cm 2 ) Activation energy R_l-Ag/GDC R_l-Ni/Ag/GDC Scaffold Activation Energy, Ea Ea-R_m (ev) Ea-R_l (ev) Ni/Ag/GDC (7.5 %vol Ni) Ag/GDC Im-Ni/GDC (11.6 %vol Ni) R_m-Ni/Ag/GDC R_m-Ag/GDC R_l-Inf-Ni/GDC R_m-Inf-Ni/GDC /T (K -1 ) Ea-influence by the composition of Ni Inf-Ni/GDC: Marina et al (2013)

13 Cell Voltage (V) Power Density (W/cm 2 ) Fuel cell performance (750 o C) %H2-50%N2 Syngas Current Density (A/cm 2 ) Electrolyte-supported cell Cathode: LSCF/GDC

14 After electrochemical measurement Ni Ni GDC (a) Ni/GDC after testing at o C and different H 2 concentrations. (b) Nickel distribution in the scaffold.

15 Conclusions Fabrication of Ni/GDC electrodes by electroless Ag following Ni electrodeposition methods was successful. -It is an alternative method for anode fabrication. -This method is also simple, fast, and requires low deposition temperature. The eletrochemical performance of the fabricated electrodes is very promising. It shows a total ASR of 1.12.cm 2 at 750 o C operating under humidified H 2. The electrodeposited Ni/GDC fuel cell is able to operate in H 2 and syngas.

16 Acknowledgement Prof. Nigel Brandon, Dr. Enrique Ruiz-Trejo & Dr. Paul Boldrin Advancing Biogas Utilization through Fuel Flexible SOFC

17 Thank you

18 Segregation of Ag from GDC porous surface and agglomeration at the surface of the GDC scaffold after heating at 800 o C in air.