Towards utilization of full solar light spectrum using green plasmonic Au–TiOx photocatalyst at ambient conditions

Abstract

Energy harvesting by utilizing the full solar light spectrum is considered Holy Grail in the field of science and the development of suitable materials to achieve this feat using environmentally benign techniques is an overwhelming challenge. In our work, we have made an attempt to prepare one such material, Au–TiOx nanocomposite, comprising of amorphous titania embedded with Au nanospheres, using a low temperature facile Green colloidal synthesis route. The prepared nanocomposite was thoroughly characterized for its structure, morphology and optical properties by using powder x-ray diffraction, Raman spectroscopy, transmission electron microscopy, photoluminescence and UV–vis spectroscopic techniques. The photocatalytic activity of the nanocomposite under ultraviolet (UV), visible, near infrared (NIR) and direct sunlight irradiation was investigated by examining the industrially important oxidative conversion reaction of methanol to formaldehyde at ambient conditions. The nanocomposite showed highest photocatalytic performance when irradiated under direct sunlight, followed by visible, UV and NIR light irradiations, respectively. The photocatalytic activity observed under UV light irradiation is due to the efficient charge separation happening between the valence and conduction bands of the amorphous titania matrix, while the activity observed under visible light irradiation can be ascribed to photosensitization by Au nanospheres and the small activity observed under NIR radiation could be attributed to plasmonic heating effects. The highest activity observed under direct sunlight irradiation is attributable to the synergistic effects of UV, visible and NIR regions present in the sunlight. This work paves way for the development of Green plasmonic photocatalysts using low temperature methods for the utilization of the total solar light spectrum.