New hydrogen-evolution heteronanostructured photocatalysts: Pt-Nb ₃O₇(OH) and Cu-Nb₃O₇(OH)

Nanorods of triniobium hydroxide heptaoxide, Nb₃O ₇(OH), were synthesized by means of a hydrothermal method. Subsequently, Pt and CuO nanoparticles were introduced on the surface of Nb ₃O₇(OH) nanorods by a microwave-assisted solvothermal nucleation and growth technique. The resulting Pt- and CuO-decorated Nb ₃O₇(OH) nanorods demonstrated uniform particle dispersion and were fully characterized by X-ray diffraction, electron microscopy, and spectroscopic analysis. Furthermore, the solar-powered photocatalytic hydrogen production properties of these heteronanostructures were studied. The solar-driven H₂ formation rate over Pt-Nb₃O ₇(OH) was determined to be 710.4±1.7 μmol g^-1 h^-1 with a quantum efficiency of φ=5.40 % at λ=380 nm. Interestingly, the as-prepared CuO-Nb₃O₇(OH) heteronanostructure was found to be inactive under solar irradiation during an induction phase, whereupon it undergoes an in situ photoreduction process to form the photocatalytically active Cu-Nb₃O₇(OH). This restructuring process was monitored by an in situ measurement of the time-evolution of the optical absorption spectra. The solar-powered H ₂ production for the restructured compound was determined to be 290.3±5.1 μmol g^-1 h^-1.