Operando XAFS study of carbon supported Ni, NiZn, and Co catalysts for hydrazine electrooxidation for use in anion exchange membrane fuel cells

Sakamoto, Tomokazu*; Matsumura, Daiju   ; Asazawa, Koichiro*; Martinez, U.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Tamura, Kazuhisa   ; Nishihata, Yasuo; Tanaka, Hirohisa*

Carbon supported Ni, NiZn, and Co hydrazine electrooxidation catalysts were synthesized by an impregnation/freeze-drying procedure followed by thermal annealing for use as anode catalyst of direct hydrazine hydrate fuel cells (DHFCs). The cell performance of DHFCs changed significantly when different catalysts were used as anode. Ammonia generation from anode outlet at open circuit voltage (OCV) condition was higher for Co/C than for Ni-based catalysts. To better understand the cause of different performance and selectivity of each anode catalyst, extensive ex-situ and operando characterization was carried out. Operando XAFS measurement of Ni-K and Co- edge shows the potential dependence of atomic structure of Ni/C, NiZn/C, and Co/C during hydrazine electrooxidation reaction.