Unbiased spontaneous solar hydrogen production using stable TiO 2 -CuO composite nanofiber photocatalysts.

We report on the optimization of electrospun TiO 2 -CuO composite nanofibers as low-cost and stable photocatalysts for visible-light photocatalytic water splitting. The effect of different annealing atmospheres on the crystal structure of the fabricated nanofibers was investigated and correlated to the photocatalytic activity of the material. The presence of CuO resulted in narrowing the bandgap of TiO 2 and shifting the absorption edge into the visible region of the light spectrum. The effect of incorporating CuO within TiO 2 nanofibers on the crystal structure and composition was also investigated using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) techniques. The fabricated TiO 2 -CuO composite nanofibers showed 117% enhancement in the amount of hydrogen evolved during the photocatalytic water splitting process compared to pure TiO 2 . This enhancement was related to the created shallow defect states that facilitate charge transfer from TiO 2 to CuO and distinct characteristics of the composite nanofibers, such as the high surface area and directional charge transfer. The study showed that Cu is a promising alternative to noble metals as a catalyst in photocatalytic water splitting, with the advantage of being an Earth abundant element and a relatively cheap material.