Adsorption of Formic Acid and Formate Anion on ZnO Nanocage: A DFT Study

By using density functional calculations, we studied the adsorption of formic acid and formate anion on a Zn12O12 nanocage in terms of energetic, electronic and geometric properties. The adsorption of cis- and trans-formic acids on the cluster is accompanied by release of energies in the range of 7.37–36.11 kcal/mol. The adsorption of trans-formic acid was found to be much more favorable than the cis-acid. It was also shown that the trans-formic acid can be dissociated to H+ cation and formate anion on the cluster surface, releasing energy of 28.08 kcal/mol. Adsorption of formate anion was found to be much more favorable than formic acids. In contrast to formic acid, the formate anion significantly influences the electronic properties of the cluster by decreasing HOMO–LUMO gap and work function. The decrement in the work function indicates that the field electron emission from the cluster surface is facilitated upon the formate adsorption.