A Mechanistic Study on the Photocatalytic Conversion of Methane to Ethane on TiO₂ and Au-TiO₂ Nano Clusters

We have studied the mechanistic pathway of methane to ethane conversion on the TiO₂ and Au-TiO₂ nano clusters using Density Functional Theory calculation. The calculated reaction energies and energy of activation on the mechanistic pathways involved in the ethane formation reaction confirm the successful conversion of methane to ethane on the TiO₂ nano cluster under normal conditions. The introduction of a gold nano cluster as a cocatalyst with the TiO₂ nano cluster reduces the energy needed for the C-C coupling step in the ethane formation reaction. In the C-H activation reaction on the Au₆-TiO₂ nano cluster, the reaction energy is almost the same as that on the bare TiO₂ nano cluster. The carbanion generated during the transition state drives the reaction forward in C-H bond activation and C-C coupling reactions. The final desorption energy of free ethane from the adsorbed surface is smaller in the case of the Au₆-TiO₂ nano cluster compared to the TiO₂ nano cluster.