Atomic and molecular adsorption on Pt(1Â 1Â 1)

The adsorption of several atomic (H, O, N, S, and C) and molecular (N2, HCN, CO, NO, and NH3) species and molecular fragments (CN, CNH2, NH2, NH, CH3, CH2, CH, HNO, NOH, and OH) on the (1 1 1) facet of platinum, an important industrial and fuel cell catalyst, was studied using self-consistent periodic density functional theory (DFT-GGA) calculations at a coverage of 1/4 ML. The best binding site, energy, and position, as well as an estimated diffusion barrier, of each species were determined. The binding strength for all the species can be ordered as follows: N2 < NH3 < HCN < NO < CO < CH3 < OH < NH2 < H < CN < NH < O < HNO < CH2 < NOH < CNH2 < N < S < CH < C. Although the atomic species generally preferred fcc sites, there was no clear trend in site preference by the molecular species or molecular fragments. The vibrational frequencies of all the stable adsorbates in their best and second best adsorption sites were calculated and found to be in good agreement with experimental values reported in the literature. Finally, the decomposition thermochemistry of NOH, HNO, NO, NH3, N2, CO, and CH3 was analyzed.