CH3O decomposition on PdZn(111), Pd(111), and Cu(111). A theoretical study

Area of Science:

• Catalysis
• Surface Science
• Computational Chemistry

Background:

• Methanol steam reforming over Pd/ZnO is a promising hydrogen source for fuel cells, especially for pollution-free vehicles.
• Understanding reaction mechanisms is key to optimizing catalytic processes.

Purpose of the Study:

• To investigate the decomposition pathways of adsorbed methoxide (CH(3)O) on Pd, Cu, and Pd-Zn alloy surfaces using density functional theory.
• To compare the energetics and transition states of competing dehydrogenation and C-O bond breaking pathways.

Main Methods:

• Density functional theory (DFT) slab model calculations.
• Computational characterization of adsorption complexes, intermediates, transition states, and products.
• Analysis of surface binding energies and energy barriers for reaction pathways.

Main Results:

• On Pd-Zn alloy surfaces, hydrogen and C-bound species favor Pd-rich sites, while O-bound species prefer Zn-rich sites.
• C-H bond scission in methoxide is kinetically favored over C-O bond breaking across all studied surfaces.
• The energy barrier for methoxide dehydrogenation is significantly higher on PdZn(111) and Cu(111) compared to Pd(111) due to weaker methoxide adsorption on Pd(111).

Conclusions:

• Methoxide decomposition to formaldehyde is thermodynamically favored on Pd(111) but endothermic on PdZn(111) and Cu(111).
• The findings provide insights into the catalytic mechanisms of methanol steam reforming, aiding in the design of efficient catalysts for hydrogen production.