Electrochemical Deposition of Pt and Pd on TiO 2 Nanotubes for Application in the Photoelectrocatalytic Conversion of Biomethane and Biogas for Hydrogen Generation

The photoelectrocatalytic conversion of biomethane/biogas using semiconductor materials is a promising method for production of green H 2 , the fuel of the future. In this work, TiO 2 nanotubes (TiO 2 NTs) prepared by electrochemical anodization were modified with Pt and Pd nanoparticles by electrochemical deposition using cyclic voltammetry, producing TiO 2 NTs/Pt and TiO 2 NTs/Pd catalysts, respectively. Evaluation of the morphology, composition, and crystallinity of the materials employed scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The photoactivities of the electrodes were studied using linear scanning voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The introduction of Pt and Pd on the TiO 2 NTs resulted in electrodes that presented excellent photogenerated charge separation and transfer properties. In the presence of methane, the current densities obtained increased further, by around 2.23- and 2.95-fold for the TiO 2 NTs/Pt and TiO 2 NTs/Pd electrodes, respectively, compared to the pure TiO 2 NTs, confirming the capacity of CH 4 to act as a hole scavenger. The maximum amounts of H 2 obtained from the photoelectrocatalytic conversion of methane were 120.7, 304.7, and 393 mmol.cm −2 for the TiO 2 NTs, TiO 2 NTs/Pt, and TiO 2 NTs/Pd electrodes, respectively, clearly showing the positive contribution of the metallic nanoparticles electrodeposited on the TiO 2 NTs surface. A lower amount of H 2 was produced in the photoelectrocatalytic conversion of biogas, with the possible occurrence of additional reactions, such as the reduction of CO 2 . Graphical Abstract