Novel visible light induced Co₃O₄-g-C₃N₄ heterojunction photocatalysts for efficient degradation of methyl orange

Novel visible-light-induced Co₃O₄-g-C₃N₄ heterojunction photocatalysts were synthesized via a facile mixing-and-heating method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), electron spin resonance (ESR) and photoluminescence spectroscopy (PL). The heterojunction photocatalysts exhibit a significantly enhanced photocatalytic activity in degrading methyl orange (MO). The optimal Co₃O₄ content with the highest photocatalytic activity was determined to be 0.2wt%. The synergetic effect between Co₃O₄ and g-C₃N₄ plays an important role in promoting photo-generated carrier separation. The ESR and PL results reveals that the enhanced photocatalytic activity of Co₃O₄-g-C₃N₄ was mainly due to the superior amount and longer lifetime of oxidative radicals (O₂^-), as well as the efficient separation of charge carriers. Possible mechanism is proposed for the high photocatalytic activity of heterojunction structures, to guide the design of photocatalysts.