Prolonging charge-separation states by doping lanthanide-ions into {001}/{101} facets-coexposed TiO2 nanosheets for enhancing photocatalytic H2 evolution

Abstract

Ultrathin TiO 2 nanosheets with coexposed {001}/{101} facets have attracted considerable attention because of their high photocatalytic activity. However, the charge-separated states in the TiO 2 nanosheets must be extended to further enhance their photocatalytic activity for H 2 evolution. Herein, we present a successful attempt to selectively dope lanthanide ions into the {101} facets of ultrathin TiO 2 nanosheets with coexposed {001}/{101} facets through a facile one-step solvothermal method. The lanthanide doping slightly extended the light-harvesting region and markedly improved the charge-separated states of the TiO 2 nanosheets as evidenced by UV-vis absorption and steady-state/transient photoluminescence spectra. Upon simulated sunlight irradiation, we observed a 4.2-fold enhancement in the photocatalytic H 2 evolution activity of optimal Yb 3+ -doped TiO 2 nanosheets compared to that of their undoped counterparts. Furthermore, when Pt nanoparticles were used as cocatalysts to reduce the H 2 overpotential in this system, the photocatalytic activity enhancement factor increased to 8.5. By combining these results with those of control experiments, we confirmed that the extended charge-separated states play the main role in the enhancement of the photocatalytic H 2 evolution activity of lanthanide-doped TiO 2 nanosheets with coexposed {001}/{101} facets. The lanthanide ions were selectively doped into the {101} facets of the TiO 2 nanosheets with coexposed {001}/{101} facets by using a one-step solvothermal method. These samples exhibited a remarkable enhancement of photocatalytic activity for H 2 evolution due to the prolonged charge-separation states, as evidenced by the kinetics analyses.