The Effects of Acid and Water in the Formation of Anodic Alumina: DFT and Experiment Study.

The DFT method is employed to study the adsorption and reaction behaviors of HCO, HPO, HSO and HO on neutral and anodic aluminum slabs. With the exception of adsorption, the three acid radicals can successively take the two H atoms from the adsorbed HO on the anodic aluminum slabs, which is the key step of the formation of anodic alumina. The dehydrogenation reaction is dominated by the Coulombic interaction of O and H, respectively belonging to acid radicals and the adsorbed HO or OH, rather than by the interaction of electronic orbits located on the two kinds of atoms. The experiment of anodic polarization of aluminum verifies the calculation result well.