Water Adsorption and Dissociation on Copper/Nickel Bimetallic Surface Alloys: Effect of Surface Temperature on Reactivity

Abstract

Water dissociation is the rate-determining step (RDS) in the industrially important water gas shift (WGS) reaction. Low temperature Cu catalysts are limited by a higher barrier to dissociation whereas Ni surfaces with lower barriers for this reaction are deactivated by carbon deposition due to CO dissociation. Density functional theory (DFT) calculations are performed on a series of overlayer and subsurface bimetallics starting with Ni(111) and Cu(111) to understand the synergistic catalytic activity of Cu/Ni bimetallics toward H 2 O dissociation which is the RDS. Surface parameters like surface energy, work function and density of states were calculated and were correlated with the change in reactivity. Transition state (TS) calculations showed that addition of Ni to Cu(111) surfaces decreased dissociation barriers while the scenario is reversed when Cu atoms replace Ni in Ni(111) surface with no linear relation with any calculated surface properties in both cases. Linear relations were found to correlate well the reaction energies with the activation energy barriers. Effects of surface temperature were included by determining the change in the barrier heights and barrier locations with lattice atom motion calculated from TS calculations. Dissociation probabilities calculated at different surface temperatures using semiclassical methods showed that increase in surface temperature increases dissociation probabilities where the extent of increase is strongly dependent on the change in barrier heights. Overall, Ni addition to Cu(111) surface proved beneficial while the Cu addition to Ni(111) surface proved detrimental to H 2 O dissociation.

Experimental Clarification of the RWGS Reaction Effect in H2O/CO2 SOEC Co-Electrolysis Conditions

“…The calculated E a,ap values are in good agreement with our previous study [46] and other studies [51][52][53] in the literature, which focus on theoretical investigations. The binary 2Fe-Ni/GDC sample is the most active for the thermochemical dissociation of H 2 O and is less resistant against bulk re-oxidation.…”

Nickel‐based Catalysts for High‐temperature Water Gas Shift Reaction‐Methane Suppression

“…who also found that barrier for C−O bond scission is strongly dependent on surface concentration of Ni on Cu. Low concentration of Ni or highly dispersed Ni on Cu can result in lower water dissociation barrier and attain higher selectivity towards WGS instead of CO methanation by increasing CO dissociation barrier as lower CO dissociation barrier favors methane formation These studies certainly provided important insights into bimetallic systems for WGS reaction but wider range of bimetallic combination of Ni‐based bimetallic catalyst are still not well explored.…”

Water Adsorption and Dissociation on Ni₃ and Ni₅ Decorated Y- and Sc-stabilized Zirconia: Insights from Density Functional Theory Investigation

“…Such mechanisms explain why a relatively smaller activation barrier was obtained for Ni 5 -ScZO system. The calculated water dissociation barriers are quite higher compared to those on Ni(100) and Ni(111) surfaces [42], but the dissociation barrier on Ni 5 -ScZO is comparable to those on Ni cluster/Cu(111) alloy [43].…”

“…In comparison to bulk Ni(100) and Ni(111) surfaces (with water adsorption energies of −0.26 eV and −0.17 eV, respectively [42]), water adsorption on these nickel clusters are more stable. Furthermore, the obtained water adsorption energies are much higher that those on Nix/Cu(111) (x = 1, 2, 3, and 4) surface alloys [43]. As such, Ni 3 and Ni 5 clusters on Y/Sc-stabilized ZrO 2 (111) are much better systems for water adsorption than bulk nickel surface and alloys.…”