Theory Study Of Reduction Of Nitrobenzene On Au（100） And The Interface Structure Of Au_n/ZrO₂

Azoaromatic compounds,due to the unique structural characteristic of the azobenzene group（the reversible photoisomerization）,have attracted considerable attention for wide applications such as dyes,information storage and nonlinear optics.A number of efforts have been made for various synthetic methods.Recent researches have found a eco-friendly feasible and efficient approach is hydrogen-transfer reduction of nitrobenzene with 2-propanol on supported nano-gold（for example Au/ZrO₂）.However,the related theoretical study appeared rarely.We investigate the reaction mechanism for the reduction of nitrobenzene towards azobenzene and the interface structure of Au_n/ZrO₂ through DFT method in this paper,expecting to provide some value information for understanding the reaction and designing the novel catalyst.In order to study the reaction mechanism for the reduction of nitrobenzene,the theoretical simulations for the migration of species and correlative elementary reaction steps are performed.The results display as follows: The parallel adsorption configuration of nitrobenzene is more stable.The diffusion of active hydrogen species is easier than nitrobenzene and nitrosobenzene,readily moving on gold catalyst to be able to interact with reactants and intermediates rather than limiting the reduction reaction rate.Our calculations indicate the direct coupling pathway of nitrosobenzene via azoxybenzene is more favored,with low energy barriers,attributing to the catalytic activity of gold.The rate-determining step is the elementary step for the cleavage of the N-O bond generating azoxybenzene,having the highest activation energy（0.60 eV）during whole reaction process.To reveal the interaction mechanism for the catalytic performance of Au/ZrO₂,we firstly explore the stable structures of Au_n/ZrO₂（n=1-16）to simulate the growth pattern of gold nanoparticles on ZrO₂ and then analyze the interfacial interaction.Our results show following information.The supported Au_n clusters on monoclinic ZrO₂（111）surface prefer quasi-planar structures,consistent with the experimental results.Both orbital overlap and dispersion interactions contribute to the interface interaction between Au_n cluster and ZrO₂ surface.The supported Au_n clusters possess a negative charge,demonstrating that electrons transfer from ZrO₂ surface to Au_n cluster.Small energy gap between the unoccupied states from Au_n clusters and the occupied states from ZrO₂ surface were found,especially for the supported Au_n clusters with odd n,which indicate that more electrons are easily excited from ZrO₂ sufrace to Au_n cluster under the visible light irradiation.Not merely the Au_n cluster but also the ZrO₂ support also participates in the photocatalytic process when using Au_n/ZrO₂ as the photocatalyst.