CO coordination at XNi4 clusters with impurities X = H, C, O. A density functional study

Area of Science:

• Computational Chemistry
• Surface Science
• Materials Science

Background:

• Nickel clusters are crucial in catalysis.
• Understanding impurity effects on metal clusters is vital for catalyst design.
• Carbon monoxide (CO) adsorption is a key chemical process.

Purpose of the Study:

• To computationally investigate the adsorption of carbon monoxide (CO) on small nickel (Ni) clusters containing single impurity atoms (H, C, or O).
• To determine the effect of these impurities on CO binding energies and vibrational frequencies.
• To provide insights for experimental identification of impurity-containing clusters.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Investigated CO adsorption configurations on bare and impurity-doped Ni4 clusters.
• Calculated binding energies and infrared (IR) frequency shifts for adsorbed CO.

Main Results:

• For bare Ni4 and clusters with H or O impurities, CO predominantly adsorbs on a Ni atom adjacent to the impurity.
• The carbon-impurity Ni4 cluster showed a preference for 3-fold coordination, only slightly more stable than on-top coordination.
• Impurities had a minor impact (up to 10% increase) on CO binding energy compared to bare Ni4.
• A significant red shift (~300 cm-1) in the CO IR frequency was predicted for carbon-impurity clusters due to altered coordination.

Conclusions:

• Heteroatoms H, C, and O exhibit a weak influence on the overall reactivity of Ni4 clusters towards CO adsorption.
• The predicted CO frequency shifts, particularly the large red shift for carbon-doped clusters, can aid experimental characterization.
• Computational results offer valuable guidance for identifying and understanding impurity effects in catalytic nickel systems.