A highly active nano black TiO ₂ photocatalyst with Pt as a co-catalyst for visible light-assisted hydrogen production from methanol–water is prepared by controlled magnesiothermic treatment in a H ₂ /Ar atmosphere.

Here, we present oxygen-deficient black ZrO_2−x as a new material for sunlight absorption with a low band gap around ~1.5 eV, via a controlled magnesiothermic reduction in 5% H₂/Ar from white ZrO₂, a wide bandgap(~5 eV) semiconductor, usually not considered for solar light absorption. It shows for the first time a dramatic increase in solar light absorbance and significant activity for solar light-induced H₂ production from methanol-water with excellent stability up to 30 days while white ZrO₂ fails. Generation of large amounts of oxygen vacancies or surface defects clearly visualized by the HR-TEM and HR-SEM images is the main reason for the drastic alteration of the optical properties through the formation of new energy states near valence band and conduction band towards Fermi level in black ZrO_2−x as indicated by XPS and DFT calculations of black ZrO_2−x. Current reduction method using Mg and H₂ is mild, but highly efficient to produce solar light-assisted photocatalytically active black ZrO_2−x.

Superhydrophobicity is of interest for practical applications such as water repellency, self-cleaning, stain resistance, antibacterial properties, and oil–water separation. In this work, a superhydrophobic coating on cotton fabric is prepared by simple immersion in TiO₂ nanoparticles and perfluorodecyltriethoxysilane solution. Its antiwetting properties, surface morphology, and functionality are characterized. The cotton fabric shows superhydrophobicity with a water static contact angle of 169.3 ± 2.1° and tilt angle of 6.3 ± 2.0°. The coating is also characterized by performing stability tests, and it shows excellent mechanical durability, chemical stability, and thermal stability. Additionally, the water droplet dynamic on the coated surface is also studied. The coated cotton fabric exhibits excellent self-cleaning, stain resistance, rust stain resistance, anti-water absorption, and antibacterial properties. It can also be used in oil–water separation with a high separation efficiency and excellent reusability.