Methane C-H Activation by Photoelectrochemical Oxidation at TiO₂ Nanotubes Arrays

Methane is mostly oxidized in order to use its heat for power generation. In order to utilize methane efficiently, it may be chemically converted for energy conversion. Unfortunately, methane’s molecular structure has neither a functional group, nor a polar distribution to facilitate chemical interactions, resulting in a low chemical reactivity. Its C-H bond has one of the highest bond energies among hydrocarbons (413kJ/mol).

An alternative approach to utilize this fuel more efficiently is by the use of fuel cell technology. This has been demonstrated for the electrochemical oxidation of methane in solid oxide fuel cells at high temperatures (650-1100℃).

The present research examines an innovative photofuelcell operating at moderate conditions (25-70℃). Titanium dioxide photoanode with a nanotube arrays structure is prepared via anodization of Ti foils followed by annealing at 500℃. This structure, which was characterized by SEM, XRD and TEM, has an efficient exposure to light with high surface area for the photocatalytic reaction. When examined by linear sweep voltammetry, this photoanode exhibits an increase of ~15% in the saturation photocurrent density (~0.5mA/cm² at +0.2V vs. Hg/HgO) in the presence of methane.