Single-step fabrication of highly stable amorphous TiO nanotubes arrays (am-TNTA) for stimulating gas-phase photoreduction of CO to methane.

This study investigates the facile fabrication of interfacial defects assisted amorphous TiO nanotubes arrays (am-TNTA) for promoting gas-phase CO photoreduction to methane. The am-TNTA catalyst was fabricated via a one-step synthesis, without heat treatment, by anodization of Titanium in Ethylene glycol-based electrolyte in a shorter anodizing time. The samples presented a TiO nanostructured array with a nanotubular diameter of 100 ± 10 nm, a wall thickness of 26 ± 5 nm, and length of 3.7 ± 0.3 μm, resulting in a specific surface of 0.75 m g. The am-TNTA presented prolonged chemical stability, a high exposed surface area, and a large number of surface traps that can reduce the recombination of the charge carriers. The am-TNTA showed promising photoactivity when tested in the CO reduction reaction with water under UV irradiation with a methane production rate of 14.0 μmol g h for a pure TiO material without any modification procedure. This enhanced photocatalytic activity can be explained in terms of surface defects of the amorphous structure, mainly OH groups that can act as electron traps for increasing the electron lifetime. The CO interacts directly with those traps, forming carbonate species, which favors the catalytic conversion to methane. The am-TNTA also exhibited a high stability during six reaction cycles. The photocatalytic activity, the significantly reduced time for synthesis, and high stability for continuous CH production make this nanomaterial a potential candidate for a sustainable CO reduction process and can be employed for other energy applications.