Amorphous tantalum oxyhydroxide homojunction: In situ construction for enhanced hydrogen production.

An amorphous tantalum oxyhydroxide TaOx(OH)y homojunction is constructed by anchoring TaOx(OH)y (2x + y = 5) nanoparticles (NPs, size: 4-10 nm) in situ on the surface of TaOx(OH)y sphere (SP). The formation of amorphous homojunction (TaOx(OH)y NPs/SP) is demonstrated by detailed characterizations of transmission electron microscopy, thermogravimetric analysis/mass spectrometer, Fourier transfer infrared spectra and X-ray photoelectron spectroscopy. In the absence of cocatalyst, the constructed amorphous homojunction exhibits a photocatalytic H2 evolution rate of 311.1 μmol/g/h, about 5, 40 and 1000 times higher than that of 66.8 μmol/g/h for bare TaOx(OH)y SP, 7.6 μmol/g/h for commercial Ta2O5, and 0.3 μmol/g/h for the most widely used photocatalyst P25 (mixed-phase titania). The splendid performance is attributed to the special amorphous homojunction that produces a type-II band alignment and robust separation of photo-excited charge carriers, as uncovered by ultraviolet photoelectron, photoluminescence spectroscopy, and surface/transient photovoltage data. Our findings for amorphous homojunction may provide a new strategy of developing effective noncrystalline photocatalysts.