Visible-light photocatalytic, solar thermal and photoelectrochemical properties of aluminium-reduced black titania

Utilizing solar energy for hydrogen generation and water cleaning is a great challenge due to insufficient visible-light power conversion. Here we report a mass production approach to synthesize black titania by aluminium reduction. The obtained sample possesses a unique crystalline core-amorphous shell structure (TiO2@TiO2-x). The black titania absorbs similar to 65% of the total solar energy by improving visible and infrared absorption, superior to the recently reported ones (similar to 30%) and pristine TiO2 (similar to 5%). The unique core-shell structure (TiO2@TiO2-x) and high absorption boost the photocatalytic water cleaning and water splitting. The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen efficiency (1.7%). A large photothermic effect may enable black titania capture solar energy for solar thermal collectors. The Al-reduced amorphous shell is proved to be an excellent candidate to absorb more solar light and receive more efficient photocatalysis.