[19p-H113-1~9] 6.5 Surface Physics, Vacuum

▲ [19p-H113-5] Hydrazine Dissociation on Ni_xMo Alloy with Pre-adsorbed OH

〇(M2)Listra Yehezkiel Ginting¹, Adhitya Gandaryus Saputro¹, Hiroshi Nakanishi¹, Wilson Agerico Dino¹, Tomokazu Sakamoto², Hirofumi Kishi², Susumu Yamaguchi², Hirohisa Tanaka², Hideaki Kasai^1,3,4 (1.Osaka Univ., 2.Daihatsu Motor, 3.Univ. of Tokyo, 4.NITAC)

Keywords:direct hydrazine fuel cell,dissociation,alloy

Understanding the catalytic reaction of hydrazine dissociation on metal surfaces is important in order to design better anode materials for direct hydrazine fuel cell (DHFC) applications. Hydrazine dissociation on the metal surface can be carried out by breaking the N-H bond, or the N-N bond. The former reaction would be more beneficial for our purpose since it produces electrons that can be used in the fuel cell. On the other hand, the latter reaction is the one that produces ammonia as unwanted by-product.
We investigated the reaction mechanism using Density Functional Theory-based calculation (DFT). We analyzed the energy barrier for the N-H bond cleaving and N-N bond cleaving on two different alloy surfaces: NiMo(001) and Ni₃Mo(001). Both on clean surfaces and surfaces with pre-adsorbed OH, the N-N bond cleaving is energetically more preferable compared to the N-H bond cleaving (Table 1). We also found that the N-N bond cleaving in NiMo requires less energy than the N-N bond cleaving in Ni₃Mo, in both cases. Based on these results, there would be more ammonia produced by NiMo than by Ni₃Mo. We also found that the presence of pre-adsorbed OH reduces the energy barrier for N-N bond cleaving, while increasing the barrier for N-H cleaving. The decrease in N-N bond cleaving barrier in Ni₃Mo is larger (0.04 eV) compared to NiMo (0.01 eV). This suggests that with higher pre-adsorbed OH concentration, there is a possibility that the N-N cleaving barrier for Ni₃Mo can be lower than NiMo. More details will be presented at the conference.