Visible Light–Induced Photocatalytic Degradation of Tetracycline over Exfoliated Graphitic C3N4 Doped with Cubic Co3O4

In this work, steam-exfoliated graphitic carbon nitride was used as a promising basis for the development of photoactive materials for processes induced by visible light. Nanocrystalline cobalt(II,III) oxide, obtained by the solution combustion method followed by heat treatment of the reaction products, was used as a cocatalyst. Nanocomposite materials were prepared by joint ultrasonic treatment of graphite-like carbon nitride and cobalt(II,III) oxide in ethanol. The prepared series of samples with different weight fractions of the oxide (5–10 wt %) was studied by powder X-ray diffractometry, scanning electron microscopy, low-temperature nitrogen adsorption–desorption, and diffuse reflectance electron spectroscopy. The photocatalytic activity of the samples was evaluated in the oxidation of tetracycline hydrochloride. It was found that the rate constant of the photocatalytic reaction reached its maximum value with composites containing 7 wt % Co₃O₄ (k = 0.0104 min^–1). The photovoltaic response studies demonstrated that the presence of cobalt oxide in the samples can significantly decrease the rate of charge carrier recombination to increase the generated current by a factor of 1.2.