Photocatalytic phenol oxidation over ball milled hexagonal boron nitride

Due to their high toxicity, even a small amount of phenols entering the surrounding aquatic environment poses a serious danger to all living beings. To address this important problem, commercial micron-sized h-BN powder was ball milled at 450, 600 and 750 rpm, surface-functionalized with hydroxyl and amino groups by sonication, and characterized as a promising photocatalyst. The samples were studied by X-Ray diffraction, Raman spec-troscopy, Fourier transform infrared spectroscopy, 11B nuclear magnetic resonance, scanning and transmission electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy and photoluminescence spectroscopy. At all rates of mechanical processing without the use of auxiliary reagents, exfoliation of h-BN flakes was ach-ieved. An increase in the ball milling rate led to a decrease in crystallinity and structure refinement, which was accompanied by the formation of a large number of dislocations and nanocrystallites 2-5 nm in size. Upon subsequent sonication, the BN powder underwent partial oxidation and functionalization with O-(H) groups. The observed increase in the photocatalytic activity of ball-milled h-BN particles in the phenol oxidation reaction is explained by an increase in the 254 nm UV-light absorption, a decrease in the rate of electron-hole recom-bination, and an increase in the formation rate of center dot OH radicals. Our results clearly show the promise of ball milled commercial micron-sized h-BN powder as a photocatalyst in the phenol oxidation reaction.