A modified MINDO/3 method was applied to the study of formic acid interactions with a nonpolar (101̄0) surface of pure zinc oxide. Molecular adsorption of both cis- and trans-HCOOH takes place on coordinatively unsaturated active sites including two-coordinated zinc cations, i.e., Zn(2C)/2+ centres. Regular (101̄0) surface of ZnO containing three-coordinated both acid and base centres are inactive at low or room temperatures; they are activated under relatively moderate temperature regions. Dissociative adsorption of HCOOH leads to the formation of a formate anion stabilized on an acid sites and of a proton connected to a basic site. For a formate anion fragment, a bridge or a bidentate structure is energetically more preferable compared to an unidentate structure. On the basis of the computational results, two channels of dissociative adsorption of HCOOH are discussed.
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