ORALS

SESSION: PhysicalThuAM-R10	Vayenas International Symposium on Physical Chemistry and its applications for sustainable development
Thu Oct, 24 2019 / Room: Aphrodite B (100/Gr. F)
Session Chairs: Antonio de Lucas Consuegra; Dimitrios Niakolas; Session Monitor: TBA

12:35: [PhysicalThuAM04]
Transition Metal Elements as Ni/GDC Dopants for the H2O Electrolysis Process in SOECs; Fe-Ni vs Au-Mo-Ni Interaction
Dimitrios Niakolas¹ ; Stylianos G. Neophytides² ; Evangelia Ioannidou¹ ; Charalampos Neofytidis¹ ; ¹Foundation for Research and Technology, Institute of Chemical Engineering Sciences (FORTH/ICEHT), Patras, Greece; ²FORTH ICE-HT, PATRAS, Greece;
Paper Id: 146 [Abstract]

High quality H₂ can be produced through water electrolysis at low or high temperatures. In this respect, solid oxide electrolysis cells (SOECs) are a promising and fast growing technology [1, 2] for H₂O electrolysis above 500°C. SOECs have identical configuration with SOFCs, but reverse operations and currently novel modified Ni-based fuel electrodes are under investigation for H₂O, CO₂ and H₂O⁺ CO₂ electrolysis applications [1, 3]. The presented study focuses on the effect of transition metal elements as dopants of the commercial NiO/GDC powder for the Solid Oxide H₂O electrolysis. Specifically, the experimental comparison is between Au [1], Mo and Fe doping. Comparative electrocatalytic measurements with I-V curves and electrochemical impedance spectra (EIS) analyses are presented in the range of 800-900°C between electrolyte-supported cells with Ni/GDC, 3Au-Ni/GDC [1], 3Mo-Ni/GDC, 3Au-3Mo-Ni/GDC, 2Fe-Ni/GDC and 0.5Fe-Ni/GDC, as the fuel electrode. Complementary physicochemical characterization was also performed both in the form of powders and as half cells with ex-situ and in-situ techniques, including specific redox stability measurements in the presence of H₂O. In summary, the cell comprising the ternary 3Au-3Mo-Ni/GDC electrode and that with 0.5Fe-Ni/GDC performed significantly better compared to the rest. The superior performance of the ternary sample is primarily ascribed to the enrichment of the surface with Au [1] and of the bulk phase with Mo, through the formation of Ni-Au-Mo solid solution [3, 4]. The involved elements act in synergy and modify the physicochemical properties of the electrode, improving the: (i) H₂O re-oxidation rate, (ii) electronic conductivity and (iii) electrochemical interface. In regards to Fe-doping, the wt.% content in iron is one key parameter. The 0.5wt.% loading of Fe results in an electrode of similar high performance to that of the Au-Mo-Ni electrode, having the great advantage of not containing gold in its composition.

References:
[1] E. Ioannidou, Ch. Neofytidis, L. Sygellou, D.K. Niakolas, Applied Catalysis B: Environmental 236 (2018) 253-264.
[2] P. Mocoteguy, A. Brisse, Int. J. Hydrogen Energy 38 (2013) 15887-15902.
[3] Ch. Neofytidis, E. Ioannidou, L. Sygellou, M. Kollia and D.K. Niakolas, Journal of Catalysis (2019), Accepted, In Press.
[4] D.K. Niakolas, C.S. Neofytidis, S.G. Neophytides, Frontiers in Environmental Science 5 (78) (2017) 1-20.