Study of ammonia decomposition in a proton conducting solid electrolyte cell

Abstract

Abstract. The reaction of NH 3 decomposition was studied at 500-700 ~ and atmospheric total pressure using a single-chamber cell-reactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form: SrCe~,95Yb00503.~,. Silver films served as cathodic and anodic electrodes. The effects of imposed current, temperature and inlet gas composition on the reaction rate were examined.

ΝΗ3 decomposition in a proton conducting solid electrolyte cell

“…The reaction exhibits an apparent activation energy of 133 ± 10 kJ mol -1 between 500 and 700°C. This value is in agreement with our previous work, in which it was found equal to 115 ± 4 kJ mol -1 between 550 and 650°C [20]. Also in good agreement are the values of the apparent reaction order calculated here and in [20], i.e.…”

“…It is worth mentioning that these high q values correspond to very low K's (K \ 2). Low K's were also observed in the single-chamber study [20]. In the latter, the q's were quite lower than those reported here (q \ 3.4).…”

“…In the latter, the q's were quite lower than those reported here (q \ 3.4). This should be expected because (a) the catalyst loading in [20] was about 8 times higher than now and (b) in the single chamber both electrodes contribute to the open circuit rate as they are both exposed to the reacting mixture.…”

“…Although numerous works on the catalytic decomposition of MH 3 can be found in the literature, only a few studies conducted in solid electrolyte cells have been reported [17][18][19][20]. Pitselis et al [17] studied the reaction using Fe as the working electrode and CaZr 0.9 In 0.1 O 3-a as the proton conductor, at temperatures between 530 and 600°C.…”

“…At 570°C and upon imposing negative currents (''pumping'' protons to the catalyst), an almost linear decrease of the reaction rate with I/2F, was observed. In a previous work in our Laboratory [20], the reaction was studied in a single-chamber cell-reactor on Ag electrodes. Hence, the data obtained therein can be combined with the present double-chamber results for a safer interpretation and understanding of the reaction mechanism.…”