Ultrasound-Assisted Synthesis of Nonmetal-Doped Titanium Dioxide Photocatalysts for Simultaneous H(2) Production and Chemical Oxygen Demand Removal from Industrial Wastewater

[Image: see text] A series of nonmetal-doped titanium dioxide (Nm(x)/TiO(2), where x is the weight fraction of nonmetal elements) photocatalysts was prepared via ultrasonic-assisted impregnation for simultaneous hydrogen (H(2)) production and chemical oxygen demand (COD) removal from industrial wastewater. Three types of Nm elements, carbon (C), silicon (Si), and phosphorus (P), were explored. The P(1)/TiO(2) exhibited a higher photocatalytic activity for H(2) production and COD removal than the C(1)/TiO(2) and Si(1)/TiO(2) photocatalysts. Approximately 6.43 mmol/g photocatalyst of H(2) was produced, and around 26% COD removal was achieved at a P(1)/TiO(2) loading of 4.0 g/L, a light intensity of 5.93 mW/cm(2), and a radiation time of 4 h. This is because the P(1)/TiO(2) photocatalyst exhibited lower point of zero charge values and a more appropriate band position compared with other Nm(x)/TiO(2) photocatalysts to produce H(+), which can consequently form H(2), and reactive oxygen species (HO(·) and O(2)(·)(–)), which serve as oxidizing agents to degrade the organic pollutants. Increasing the content of the P element doped into the TiO(2)-based material up to 7.0% by weight enhanced the H(2) production and COD removal up to 8.34 mmol/g photocatalyst and 50.6%, respectively. This is attributed to the combined effect of the point of zero charge value and the S(BET) of the prepared photocatalysts. The photocatalytic activity of the P(7)/TiO(2) photocatalyst was still higher than the TiO(2)-based material after the fourth use.