Photo enhanced methanol electrooxidation: Further insights into Pt and TiO 2 nanoparticle contributions

Pt nanoparticles (PtNPs) were deposited on two different supports: Vulcan® XC-72R carbon (PV) and TiO2/G-PV, a TiO2/carbon composite support prepared using glucose-doped Vulcan® XC-72R carbon (G-PV). The presence of TiO2 has been shown to maximize the PtNPs specific surface area and improves the catalytic performance through Pt-metal oxide interaction. The catalytic activity of Pt/TiO2/G-PV and Pt/PV toward the methanol oxidation reaction (MOR) was investigated with and without ultraviolet-visible (UV–vis) light irradiation using different electrochemical techniques. The results show the enhancement in catalytic activity in Pt/PV under illumination (Ipeakillumination-Ipeakdark)*100/Ipeakdark ∼ 100%) can be attributed to a significant reduction in the charge transfer resistance (Rct) when the electrode is illuminated (635 Ω (dark) vs 84 Ω (illumination)) as determined by electrochemical impedance spectroscopy (EIS). The observed photo enhancement is relatively modest when compared to the Pt/TiO2/G-PV catalyst (Ipeakillumination-Ipeakdark)*100/Ipeakdark ∼ 171%), even though the change in the Rct (185 Ω vs. 99 Ω) is not as pronounced as in the Pt/PV samples. The carbon monoxide (CO) stripping results indicate that illumination aids the removal of adsorbed CO from the PtNPs surface. The remarkable enhancement on the oxidation of methanol under UV–vis illumination in the case of the Pt/TiO2/G-PV catalyst materials show the potential of these materials for applications such as disposable and portable electrochemical sensors for water analysis, mainly the determination of organic contaminants in water. Moreover, it can be a breakthrough in the development of novel photoelectrochemical ethanol sensors and a new generation of energy conversion devices.