Effect of Hydrogen in Adsorption and Direct Dissociation of CO on Fe (100) Surface: A DFT Study

Abstract

Density functional theory was employed to investigate the effect of the hydrogen in the adsorption and direct dissociation of CO on Fe (100) surface. The preadsorption of hydrogen with coverages of 0, 1/3 and 2/3 monolayer (ML) was used in the present investigation. In the case of 1/3 ML of hydrogen, two configurations of adsorption were studied. The presence of hydrogen shows a major transference of electronic density from Fe surface to CO adsorbed, increasing the adsorption energy of CO from 2.00 eV in clean surface, to 2.76 eV in 2/3 ML of hydrogen. Furthermore, the activation barrier for direct dissociation of CO was 1.13 eV and for the recombination energy 2.28 eV on clean Fe (100) surface. In the same way, the activation barrier for CO in the presence of coadsorbed hydrogen was slightly affected presenting values of 1.06 eV and 1.16 eV to 1/3 ML configurations and 0.98 eV for 2/3 ML of hydrogen. Finally, the recombination energy decreases to 1.63 eV and 1.49 eV for 1/3 ML configurations and to 1.23 eV for 2/3 ML of coadsorbed hydrogen. These results indicate that the CO adsorption and dissociation are favored in the presence of hydrogenated surfaces.

DFT study of adsorption and diffusion of atomic hydrogen on metal surfaces

“…The first three layers were fixed at the bulk position and the other two were allowed to relax describing the (100) surface where H is adsorbed. Hydrogen-adsorption energy is converged for a p(2x2) model in good agreement with calculations of H adsorption on F e(100) performed by Amaya et al [19,20,21] and by Sorescu [29].…”

“…Ferrin et al [3] have investigated diffusion of hydrogen from the surface to the bulk using the P W 91 density functional [15], whereas Kristinsdóttir et al [4], have studied surface diffusion on several metals by means of RPBE [16]. In addition, the calculations performed with GGA-PBE functionals, have been widely accepted in the scientific community and have been extensively used in systems with periodic boundary conditions [17,18,19,20,21]. Even with the mentioned references, the fcc (100) surfaces of Au, Cu, Ag and P t,…”

Influence of surface vacancy defects on the carburisation of Fe 110 surface by carbon monoxide

“…This topic has been revisited by a number of recent works. [23][24][25][26][27] While a dense CO-coverage (≤0.25 monolayer) is commonly considered, we have shown that the dissociation barrier is greatly reduced at a dilute coverage (up to 0.0625 monolayer), 28 due to the unrestricted relaxation of the Fe lattice. However, the presence of intrinsic defects is a likely candidate that can significantly affect the carburisation process and has not been considered yet.…”

Insights on finite size effects in ab initio study of CO adsorption and dissociation on Fe 110 surface

“…In practice, more complex reaction pathways would be possible as a number of other molecules and sites that could act as activator, such as H and other reactive hydrocarbons and surface defects, are generally present and could assist the dissociation process [13,14]. Recent works on the 100 surface show that high-coverage presence of H increases the rate of carburization by reducing the dissociation barrier [13,15]. On the other hand Cu impurities on the surface increase the dissociation barrier and prevent C atoms to be adsorbed into the surface [14].…”

“…After almost a decade, this topic has been revisited by many researchers in recent years [10,11,[13][14][15]26]. There are several reasons for this renewed interest, of which, notable from the perspective of computational science, is the advancement in computational power that is necessary for surface calculations with the computationally demanding nudged elastic band method.…”