First-Principles Investigation of the Molecular Adsorption and Dissociation of Hydrazine on Ni–Fe Alloy Surfaces

Abstract

We have used density functional theory (DFT) with dispersion correction to investigate the adsorption and first dissociation step of hydrazine on Fe 3 Ni(111), FeNi(111), and FeNi 3 (111) surfaces. The calculations have shown that the FeNi 3 (111) surface offers the strongest binding of molecular hydrazine adsorbed on the top of an iron atom, whereas the strongest adsorption of NH 2 fragment bridging between iron atoms is obtained on the Fe 3 Ni(111) surface; both molecular hydrazine and the NH 2 fragment can be adsorbed strongly on the FeNi(111) surface.The first dissociation step of hydrazine on the FeNi(111) surface is found to be exothermic by −1.19 eV and presents an activation energy barrier of only 0.15 eV. A similar energy barrier is found on the Fe 3 Ni(111) surface, but a higher reaction energy of −1.47 eV is released on this surface. Furthermore, the electronic structures of the molecular and dissociative adsorptions are discussed, which is intended to shed some light on the binding nature of the adsorption and stability among conformations of the adsorbed molecule on these surfaces. It is expected that our results will provide useful information for the development of a catalyst for hydrazine dissociation.

Atomically ordered non-precious Co3Ta intermetallic nanoparticles as high-performance catalysts for hydrazine electrooxidation

“…It can be seen that the Co K-edge and Ta L 3 -edge X-ray absorption edge energy is arranged in the order of Co 3 O 4 > CoO > Co 3 Ta ≈ Co foil and Ta 2 O 5 > Co 3 Ta ≈ bulk Ta powder. The bader charge calculation 47,48 by using DFT method also confirms the slight charge transfer between Co and Ta in Co 3 Ta, as shown in Supplementary Table 3. Despite the net gain of charge in the electron count from Ta due to the difference in electronegativity between Ta and Co, the Co absorption edge energy in Co 3 Ta exhibits no significant negative shift with respect to that of bulk metallic Co, which is consistent with the previous works 49,50 , and the Ta absorption edge energy in Co 3 Ta also exhibits a small positive shift with respect to that of bulk metallic Ta.…”

Hydrogen Production via Hydrazine Decomposition on Model Platinum–Nickel Nanocatalyst with a Single (111) Facet

“…Possible reaction mechanisms were proposed for the catalytic hydrazine decomposition in previous studies. − It is generally believed that the reaction on metal surfaces initiates from adsorption of hydrazine molecules, which then dehydrogenate by breaking the N–H bonds and generate N 2 H x (1 ≤ x ≤ 3) intermediates and adsorbed hydrogen species. A complete dehydrogenation of the N 2 H x intermediates and recombination between adsorbed hydrogen atoms lead to the generation of final products, N 2 and H 2 .…”

Hydrazine Oxidation Electrocatalysis

“…126 High-index facets are often catalytically active due to significant unsaturation in the surface atom bonds. 78,79,128,129 For example, the high-index Au(511) surface, formed on concave Au single-crystalline nanoparticles, is more active toward the HzOR than Au spheres, both in alkaline and acid electrolytes (Figure 4f). 128 Methods for nanoparticle synthesis also enable growing core−shell 88,130,107,131,110 or multicomponent, high-entropy alloys.…”

“…Although hydrazine is thermodynamically unstable, its decomposition in air is negligible. , Acidic conditions promote its decomposition to NH 3 , H 2 , N 2 , and HN 3 , although it occurs in alkaline pH, too . According to DFT calculations, hydrazine coordinates to transition-metal surfaces through a nitrogen lone-pair. , However, these surfaces are expected to be oxidized, and the effect of oxidation on reaction selectivity (toward N 2 /NH 3 /NO x ) is hard to predict and could be opposite on real (e.g., nanostructured) surfaces. , Moreover, in an electrolyte environment the hydrogen bonding will also affect the adsorption preferences of hydrazine, − while higher temperatures could promote faster decomposition …”

“…Mechanistic HzOR studies are harder to perform on nanoparticles than on single-crystalline metal surfaces, since the high-energy surface of nanoparticles is typically less defined and even more in flux during catalysis. Theoretical calculations predict that the selectivity of the oxidation and decomposition routes will depend on the exposed metal facet and the local structure. − ,,− Thus, precise control of the nanoparticle shape could expose specific crystal facets or active defects and even tune their electronic structures. This has been demonstrated experimentally for shape-selected single-crystalline nanoparticles, such as the Pd(110) or the Rh(100) surfaces, which were found to be more active toward the HzOR than other facets.…”