Onion-like carbon-modified TiO2 coating by suspension plasma spray with enhanced photocatalytic performances

Onion-like carbon (OLC), a novel carbonaceous nanomaterial, has already attracted widespread concern due to its exceptional physicochemical properties. In this work, OLC nanoparticles (5-10 nm in diameter) were used as additives to fabricate nanotitania (TiO2) coatings by suspension plasma spray (SPS) for photocatalytic degrading methylene blue. The starting microstructure and chemistry of both OLC and TiO2 nanoparticles were retained after deposition process, and homogeneous dispersion of OLC in the coating was detected, which indicates SPS is an alternative and efficient technique to fabricate semiconductor-carbonaceous nanomaterials coatings. The new TiO2-OLC composite shows typical mesoporous structure. And aligned interfacial bond of OLC spheres with the (101) plane of anatase crystals was revealed. TiO2-OLC shows enhanced activity of degrading methylene blue under both UV and visible light irradiation than pure TiO2 coating. We have elucidated the enhancement mechanism from three aspects, namely, reduction of the bandgap, minimization of photo-induced-carriers recombination, and promotion of adsorption capacity for methylene blue.