TiO 2 hollow spheres with surface-rich Ti 3+ under Pd-catalyzed hydrogenation for improved visible-light photocatalysis

Abstract

To enhance the utilization of visible light and prevent photogenerated electrons/holes from recombination, black TiO₂ hollow spheres of varying shell thicknesses rich in Ti³⁺ were synthesized via hydrogenation with the aid of Pd. With increasing hydrogenation temperature from room temperature to 200 °C, the thickness of the disordered layer increases, and the concentration of Ti³⁺, which is the main active site for photocatalysis, also increases. Owing to the intense visible-light harvesting nature and rich active sites introduced by the disordered layer, the black TiO₂ hollow spheres obtained at 200 °C degrade rhodamine B (RhB) to 95.2% within 120 min under visible-light illumination. In addition to the role of enhanced visible-light absorbance, Ti³⁺ also improves the conductivity, which is further confirmed with Li-ion batteries. The enhanced conductivity favors the separation of photogenerated electrons/holes.

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