The structure and composition of metal surfaces play a crucial role in the selectivity of the oxidation reaction of hydrocarbons. This is because the metal surface acts as a catalyst, and its properties can influence the reaction pathway and the products formed. Several factors contribute to this effect:1. Metal type: Different metals have different electronic structures and properties, which can affect their ability to adsorb and activate hydrocarbon molecules. For example, noble metals like platinum and palladium are known to be highly active for hydrocarbon oxidation, while base metals like copper and nickel are less active.2. Surface structure: The arrangement of atoms on the metal surface can influence the adsorption and activation of hydrocarbon molecules. For example, a stepped surface with a higher density of under-coordinated atoms may provide more active sites for the reaction, leading to higher selectivity.3. Crystallographic orientation: The crystallographic orientation of the metal surface can also affect the selectivity of the oxidation reaction. Different crystal planes may have different surface energies and electronic properties, which can influence the adsorption and activation of hydrocarbon molecules.4. Surface composition: The presence of other elements on the metal surface, such as oxygen or other metal atoms, can modify the electronic properties and reactivity of the surface. This can lead to changes in the selectivity of the oxidation reaction. For example, the addition of small amounts of gold to a platinum surface can enhance the selectivity of propylene oxidation to acrolein.5. Particle size and morphology: The size and shape of metal particles can also influence the selectivity of the oxidation reaction. Smaller particles typically have a higher proportion of under-coordinated atoms, which can lead to higher activity and selectivity. Additionally, the shape of the particles can affect the distribution of crystallographic planes exposed on the surface, which can influence the reaction pathway.6. Support effects: The metal catalyst is often supported on a material like alumina, silica, or zeolite. The support can influence the dispersion of the metal particles, their electronic properties, and the accessibility of reactants to the active sites, all of which can affect the selectivity of the oxidation reaction.In summary, the structure and composition of metal surfaces play a significant role in determining the selectivity of hydrocarbon oxidation reactions. By carefully controlling these factors, it is possible to design catalysts with improved selectivity for specific reactions, leading to more efficient and sustainable chemical processes.