Positive Ni(HCO₃)₂ as a Novel Cocatalyst for Boosting the Photocatalytic Hydrogen Evolution Capability of Mesoporous TiO₂ Nanocrystals

A highly efficient hybrid photocatalytic system consisting of Ni­(HCO₃)₂ and mesoporous TiO₂ microrods was successfully fabricated by a hydrothermal approach. The involvement of Ni­(HCO₃)₂ cocatalyst resulted in significant improvement of the hydrogen evolution on the host TiO₂ photocatalyst under artificial sunlight irradiation. The optimized hybrid photocatalysis system with 2.5% (mole ratio) Ni­(HCO₃)₂ loading displayed the highest hydrogen evolution rate of 1798.0 μmol g^–1 h^–1, which was more than 18 times higher than that of pure mesoporous TiO₂. On the basis of the photoluminescence spectroscopy and photoelectrochemical measurement results, it is proposed that the enhancement of photocatalytic hydrogen evolution capability on the TiO₂–Ni­(HCO₃)₂ host photocatalyst–cocatalyst is not only attributed to the efficient separation of photoinduced electron–hole pairs, but also derived from the Ni­(HCO₃)₂ cocatalyst acting as active reaction sites toward hydrogen production