Synthesis of Crystallized Mesoporous Tantalum Oxide and Its Photocatalytic Activity for Overall Water Splitting under Ultraviolet Light Irradiation

The well-ordered two-dimensional hexagonal (2D-hex) structure of mesoporous Ta2O5 was maintained after crystallization with the aid of SiO2 reinforcement, which was removed after crystallization. The photocatalytic activity of the mesoporous Ta2O5 for overall water splitting under ultraviolet (UV) irradiation was improved by changing the solid phase structure from amorphous to crystalline by nearly 1 order of magnitude. The resulting photocatalytic activity of NiOx(3.0 wt %)-loaded crystalline mesoporous Ta2O5 for water decomposition (3360 μmol·h−1 of H2 and 1630 μmol·h−1 of O2 evolution at the initial 1 h) was found to show one of the highest activities among so far reported photocatalysts under similar conditions. The high activity is attributable to the efficient transfer of the excited electrons and holes from inside to the surface of the catalyst through thin-walled crystalline phase.