ΝΗ3 decomposition in a proton conducting solid electrolyte cell

Abstract

The reaction of NH 3 decomposition was studied on Ag in a proton conducting double chamber cellreactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form SrCe 0.95 Yb 0.05 O 3-a . The reaction was studied at 350-700°C and atmospheric total pressure. The proton transference number (PTN) was calculated by simultaneous measurement of the imposed current and the proton flux and it was found to vary between 0.5 and 0.7. The effects of imposed current, temperature and inlet gas composition on the reaction rate and the PTN, were examined. Although the faradaic efficiency (K) remained near unity in all experiments, reaction rate enhancements (q) as high as 57 were achieved. An up to 90% decrease in the activation energy of the reaction was observed when protons were electrochemically ''pumped'' away from the catalyst.

Electrochemical Synthesis of Ammonia in Solid Electrolyte Cells

“…Zisekas et al studied the reaction on Ag electrodes. Although the Λ's remained near unity in all experiments, ρ values as high as 57 were achieved (Zisekas et al, 2008).…”

“…Ammonia is a pure hydrogen source for fuel cell applications. To this end, solid state H + conducting cells were used to study the decomposition of NH 3 on Ru (Skodra et al, 2006), Fe (Pitselis et al, 1997), and Ag (Zisekas et al, 2008) electrodes. Moreover, the idea to use NH 3 as a fuel was tested in both H + and O 2− solid electrolyte cells with promising results (McFarlan et al, 2004;Pelletier et al, 2005).…”

Electrocatalytic synthesis of ammonia from steam and nitrogen at atmospheric pressure

“…Thus far, reaction (1) has been studied in solid state proton conducting cells: a) on Pd electrodes by using a SCY electrolyte [19,25], b) on an industrial iron catalyst by using either a CaZr 0.9 In 0.1-O 3 − a [20,37], or a strontia-zirconia-yttria proton conductor [24], c) on Ag electrodes using a SCY electrolyte [38,39] and d) on Ag-Pd electrodes by testing various oxide-salt composites as proton conductors [21][22][23]. In all these studies, the overall cell reaction was reaction (1), i.e.…”

Enhancement of Ammonia Synthesis on a Co3Mo3N-Ag Electrocatalyst in a K-βAl2O3 Solid Electrolyte Cell

“…A large number of papers on the electrochemical synthesis of ammonia have been published in the past two decades. ,, Nevertheless, in only a few of them a gaseous mixture of hydrogen and nitrogen, rather than pure nitrogen, was introduced at the cathode. Therefore, very few studies focused on the EPOC effect either for the forward reaction of NH 3 synthesis ,,, or for the reverse reaction of NH 3 decomposition. − Yiokari et al used a single-chamber reactor and studied the reaction on a commercial Fe catalyst. Upon “pumping” H + to the catalyst surface, the reaction rate could increase by as much as 1300% (ρ = 14).…”

“…The EPOC effect on catalytic decomposition of NH 3 has been studied on Pd, Ru, Ag , using proton (H + ) conducting cells and on Fe using both, H + and K + conductors . On a Ag electrode, although Λ remained near unity, reaction rate enhancements (ρ) as high as 57 were achieved .…”