Hydrogen Adsorption on Pt(111) Revisited from Random Phase Approximation

It is generally believed that H is predominantly adsorbed on the fcc site of Pt(111), as supported by the calculations using density functional theory (DFT) within generalized gradient approximation (GGA). Experiments, however, observe the signal from the top site. Similar problem exists in CO/Pt(111), where GGA is known to wrongly predict the fcc site as the most stable site, for which a correct answer was given recently using a more advanced correlation functional called random phase approximation (RPA). Here we attack this H/Pt(111) problem using DFT-RPA [1]. By using DFT within the exchange-correlation functionals of different level, we evaluate the stability of fcc adsorption site relative to the top site. The most advanced one based on the RPA, is found to revise our knowledge so far derived from the conventional functionals. Two adsorption sites are hereby found to compete sensitively depending on lattice spacing of the surface, mass of the hydrogen isotope, and hydrogen coverage. The revised knowledge provides natural explanation for the controversy regarding the electrochemical and spectroscopic data, giving impact on the research on the fuel-cell reaction mechanism.
[1] L. Yan, Y. Sun, Y, Yamamoto, S. Kasamatsu, I. Hamada, O. Sugino, J. Chem. Phys. 149, 164702 (2018).