Theoretical study of H2PO2− adsorption on Ni(111) and Cu(111) surfaces

Surface structures and electronic properties of hypophosphite, H2PO2−, molecularly adsorbed on Ni(111) and Cu(111) surfaces were investigated using B3LYP density functional theory. Geometry and orientation of H2PO2− were fully optimized on the metal clusters and six and four stable structures were obtained on Ni(111) and Cu(111) surfaces, respectively. The most stable structures were that H2PO2− is absorbed with its two P-O bonds in faced to the substrate surface and with O atoms in bridge sites. The adsorption energy was more larger on the Ni surface than on the Cu surface. The results of the Mulliken population analysis showed that the donation from lone pair of O atom in H2PO2− to substrate and the 4s back donation from substrate to H2PO2− σ* play very important roles in the adsorption, and that the amounts of both donation and back donation were larger on the Ni surface than on the Cu surface. There were more negative Mulliken charge transfers from H2PO2− to substrate clusters on Ni substrate clusters than on Cu substrate clusters and were more positive Mulliken charges on P atom in Ni4H2PO2− than in Cu4H2PO2−, which means that P atom in Ni4H2PO2− are easily attacked by nucleophile such as OH−, and farther H2PO2− were more easily oxidated on Ni substrate than on Cu substrate.