A density functional theory investigation of the molecular and dissociative adsorption of hydrazine on defective copper surfaces

Abstract

Density functional theory calculations of the adsorption of hydrazine (N₂H₄) on the copper (111), (100) and (110) surfaces have shown that the surface structure is key in determining the thermodynamics of adsorption, with low coordinated atoms, resulting from the surface geometry, providing sites for strong adsorption. Although the uneven structure of the (110) surface allows for the strongest binding of molecular hydrazine through bridging between surface atoms, the addition of adatoms to the otherwise more stable and flatter (111) and (100) surfaces provides sites that enable binding to almost the same extent. The thermodynamics of dissociative adsorption by breaking of the hydrazine N–N bond show that this binding mode is strongly favoured over molecular adsorption both on the planar surfaces and at the adatoms. The strength of adsorption is shown to increase with decreasing surface stability, with adsorption energies for dissociative adsorption ranging from 229 kJ mol⁻¹ to 257 kJ mol⁻¹, whereas molecular hydrazine adsorbs with the release of 94 kJ mol⁻¹ to 107 kJ mol⁻¹.