TiO2 with controlled nanoring/nanotube hierarchical structure: Multiabsorption oscillating peaks and photoelectrochemical properties

•TiO2 with controlled nanoring/nanotube hierarchical structures are fabricated.•TiO2 R/T structure has the unique multiple light reflection characteristics.•The optical path length in TiO2 R/T structure is estimated as about 2μm.•The tube-wall thickness affects the photocurrent-saturation potential.•The visible light activity of TiO2 R/T structure is more related to defects.