First-principles study on the geometry and stability of CO and hydrogen coadsorption on the Ni(1 1 1)2 × 2 surface

Periodic, self-consistent, density functional theory (GGA-PW91) calculations are performed for hydrogen and carbon monoxide coadsorption on Ni(1 1 1). It was found that the hollow sites are energetically preferred in pure H/CO adsorption system. In the co-adsorbed phase, the best-fit geometry is that CO molecule sits in hcp hollow and hydrogen atom occupies fcc site. The adsorption states and the optimized geometries are found to be in excellent agreement with experimental results. In coadsorption system, the calculations show a blue shift of 36 cm−1 relative to the pure CO adsorption phase for the CO stretching frequency. The calculated Ni-C stretching frequency shift directions in Ni(1 1 1) and Ni(1 0 0) are reversed. The Density of State (DOS) analysis has shown that there is charge redistribution in coadsorption system upon hydrogen adsorption on the CO/Ni(1 1 1) surface.