Methane, the primary component in natural gas, has extensive utilities in the chemical industry and as an energy source. The depletion of petroleum reserves highly motivates the exploitation of natural gas as an important hydrocarbon feedstock with a small environmental footprint. However, this potential energy source is being wasted due to the lack of an efficient utilization process that will integrate natural gas in the existing energy infrastructure. Methane is mostly burned 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 investigates the photoelectrochemical oxidation of methane at anodized Ti photoanodes. TiO₂ semiconductor generates highly reactive holes upon illumination that can drive the oxidation reaction. In this type of activation, the exploitation of light energy may dramatically reduce the energy required for the oxidation reaction. TiO₂ photoanodes with a nanotube arrays structure are 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, as compared to that obtained in the presence of an inert gas (water oxidation).