Rapid Hydroxyl Radical Generation on (001)-Facet-Exposed Ultrathin Anatase TiO2 Nanosheets for Enhanced Photocatalytic Lignocellulose-to-H2 Conversion

Photocatalytic lignocellulose-to-H-2 conversion is highly attractive but remains a huge challenge due to the absence of efficient photocatalysts. Herein we report the use ultrathin anatase TiO2 nanosheets with a thickness of 2.1 nm and 94.5% exposed (001) facets (TiO2-1) as highly active photocatalysts for photocatalytic lignocellulose-to-H-2 conversion. The ultrathin structure of TiO2 not only provides abundant active sites for the photocatalytic H-2 production reaction but also benefits photogenerated charge transfer to the surface. Furthermore, as proven by theoretical calculations and fluorescence experiments, the center dot OH radicals acting as the key species for the oxidation of lignocelluloses can be easily generated on the (001) facets owing to the low activating energy for the center dot OH generation reaction. Notably, the highest photocatalytic H-2 generation rates of 275 and 26 mu mol.h(-1).g(-1) were achieved, respectively, in 250 mL of 4g.L-1 alpha-cellulose solution and poplar wood chip aqueous solution consisting of 100 mg of 1.0% Pt-loaded TiO2-1 photocatalyst, and an apparent quantum yield of 1.89% at 380 nm was achieved in alpha-cellulose aqueous solution. The photocatalytic H-2 production activity of TiO2-1 is about 2.4 and 2.1 times higher than that of reference TiO2 nanosheets (TiO2-2) in alpha-cellulose solution and poplar wood chip solution, respectively. Our findings demonstrate the feasibility of establishing rapid center dot OH generation to boost the oxidation of lignocelluloses and to enhance lignocellulose-to-H-2 conversion.

Automated summary

In this study, ultrathin anatase TiO2 nanosheets with exposed (001) facets were used as highly active photocatalysts for photocatalytic lignocellulose-to-H-2 conversion. The ultrathin structure provided abundant active sites and facilitated photogenerated charge transfer. The generation of ·OH radicals on the (001) facets was proven to be feasible. The findings demonstrated the potential of rapid ·OH generation to enhance lignocellulose oxidation and hydrogen production.