Defect‐induced Ordered Mesoporous Titania Molecular Sieves: A Unique and Highly Efficient Hetero‐phase Photocatalyst for Solar Hydrogen Generation

Abstract

AbstractThe conversion of solar energy into fuel has gained significant interest, particularly in photocatalytic water splitting, and the materials that efficiently generate hydrogen from water or aqueous solution using solar irradiation are highly desired for the hydrogen economy. Photocatalysts made of N‐doped TiO2 are frequently utilized for breaking of water molecules in the process of generating hydrogen. To achieve this target, a unique defect‐induced nitrogen‐doped highly organized 2D‐hexagonal periodic mesoporous titania, TiO2‐xNy with a well‐crystallized framework is synthesized in a reproducible way using structure‐directing agents, e. g., F108, F127, P123, and CTAB. The nitrogen is incorporated into these samples through a facile method involving the calcination of templated materials in an air. A systematic characterization of the resulting ordered mesoporous titania employing a battery of experimental techniques indicates the presence of considerable amounts of intrinsic defects, viz., trapped electrons in oxygen vacancy and/or Ti3+ centres via nitrogen‐doping in the titania matrix. These defects in turn promote the charge separation of photogenerated excitons, and therefore exhibit excellent photocatalytic activity for the hydrogen evolution reaction as compared to commercial titania such as Aeroxide®P‐25. The superior activity of the N‐doped mesoporous TiO2 is attributed to the synergistic effect of facile charge migration with high carrier density, unique phase composition (bronze and anatase), slow recombination of photo‐induced excitons, and enhanced absorbance from ultra‐violet to the visible region.