MoSexOy-Coated 1D TiO2 Nanotube Layers: Efficient Interface for Light-Driven Applications

Abstract

Ultrathin molybdenum oxyselenide (MoSexOy) coatings were made first ever by atomic layer deposition (ALD) within anodic 1D TiO2 nanotube layers for photoelectrochemical and photocatalytic applications. The coating thickness was controlled through varying ALD cycles from 5 to 50 cycles (corresponding to ~1 to 10 nm). In the ultraviolet region, the coatings have enhanced up to 4 times the incident photon to current conversion efficiency (IPCE), and the highest IPCE was recorded at 32% at (at λ = 365 nm). The coatings notably extended the photoresponse to the visible spectral region and remarkable improvement of photocurrent densities up to ~40 times was registered at λ = 470 nm. As a result, the MoSexOy coated-TiO2 nanotube layers have shown to be an effective photocatalyst for methylene blue (MB) degradation, and the optimal performance was credited to a coating thickness between 2 to 5 nm (feasible only by ALD). The enhancement in photo-activities of the presented heterojunction is mainly associated with the passivation effect of MoSexOy on the TiO2 nanotube walls and the suitability of bandgap position between MoSexOy and TiO2 interface for an efficient charge transfer. In addition, MoSexOy possesses a narrow bandgap, which favors the photoactivity in the visible spectral region.