Electron density topological and adsorbate orbital analyses of water and carbon monoxide co-adsorption on platinum

Abstract

The electron density topology of carbon monoxide (CO) on dry and hydrated platinum is evaluated under the quantum theory of atoms in molecules (QTAIM) and by adsorbate orbital approaches. The impact of water co-adsorbate on the electronic, structural, and vibrational properties of CO on Pt are modelled by periodic density functional theory (DFT). At low CO coverage, increased hydration weakens C–O bonds and strengthens C–Pt bonds, as verified by changes in bond lengths and stretching frequencies. These results are consistent with QTAIM, the 5σ donation-2π* backdonation model, and our extended π-attraction σ-repulsion model (extended π-σ model). This work links changes in the non-zero eigenvalues of the electron density Hessian at QTAIM bond critical points to changes in the π and σ C–O bonds with systematic variation of CO/H2O co-adsorbate scenarios. QTAIM invariably shows bond strengths and lengths as being negatively correlated. For atop CO on hydrated Pt, QTAIM and phenomenological models are consistent with a direct correlation between C–O bond strength and CO coverage. However, DFT modelling in the absence of hydration shows that C–O bond lengths are not negatively correlated to their stretching frequencies, in contrast to the Badger rule: When QTAIM and phenomenological models do not agree, the use of the non-zero eigenvalues of the electron density Hessian as inputs to the phenomenological models, aligns them with QTAIM. The C–O and C–Pt bond strengths of bridge and three-fold bound CO on dry and hydrated platinum are also evaluated by QTAIM and adsorbate orbital analyses.

A quantum chemical study of substituent effects on CN bonds in aryl isocyanide molecules adsorbed on the Pt surface

“…Therefore, we examine the electron transfer process during the formation of a chemical bond This newly presented model has been used to explicitly explain the C−O and C−metal bond strengths of CO adsorbed on Pt−Os binary alloy and Pt−Ru−Os tertiary alloy, 82 and PtRuOsIr quaternary, 83 on PtRu alloys, 84 and Pt(100) and Ru(0001) surfaces, 85 as well as water and CO coadsorbed on Pt(111) surface at various coverages. 86 To characterize the substituent effect on the NC stretching frequency and bond order concisely, we discuss the donation and back-donation strengths based on a localized perspective of chemical bonding in a quantitative manner. The occupancy change also appears in the σ* antibonding orbital (see Fig.…”

Structural Evolution and Magnetic Properties of Gd2Hf2O7 Nanocrystals: Computational and Experimental Investigations

“…Details regarding the Brillouin zone integrations grids can be found in the Supplementary Materials . SCF energy convergence and geometry optimization parameters are described in our past work [ 66 , 67 ].…”

Direct Urea Fuel Cells: Recent Progress and Critical Challenges of Urea Oxidation Electrocatalysis

“…Furthermore, the chemisorbed intermediates on the catalyst's surface electronically modify the neighboring active sites and hinders the urea molecules’ adsorption, lowering the fuel utilization efficiency. [ 54–56 ] An approach to prevent this poisoning scenario lies in the promotion of suitable designs and engineering formulations to the catalyst surface. Alloying the metal catalyst with other transition metals, heteroatom doping, and chemical modification of catalyst surface (atomic ensemble effect) can electronically weaken the MCO bond, ensuring a prolonged use of the electrocatalyst without poisoning.…”