Carbon spheres supported visible-light-driven CuO-BiVO ₄ heterojunction: Preparation, characterization, and photocatalytic properties

To utilize visible light more effectively in photocatalytic reactions, carbon-supported CuO-BiVO ₄ (CuO-BVO@C) composite photocatalyst was prepared by hydrothermal process and impregnation technique. The photocatalytic activities of as-prepared catalysts were evaluated by degradation of methylene blue (MB) in aqueous solution under visible light irradiation, it was found that CuO-BVO@C exhibits the highest photocatalytic degradation activity with the pseudo-first-order rate constant K _a five times higher than pure BiVO ₄, which could be assigned to the synergistic effect of CuO-BiVO ₄ heterojunction and carbon spheres. The characterization of photocatalysts by a series of joint techniques, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectra, PL spectra and electrochemistry technology, discloses that carbon spheres play two crucial roles in enhancing of photocatalytic activity. One is to act as a dispersing support to suppress the grain growth, the other is to act as a photosensitizer to transfer the electrons to CuO-BiVO ₄ heterojunction, which narrows the band gap of BiVO ₄, hinders the electron-hole pair's recombination, extends the absorption range of visible light, and improves the photocatalytic performance of catalyst. The photocatalytic degradation pathways mainly involve the formation and reaction of OH radicals. Based on the experimental results of electron spin-resonance spectroscopy, a reasonable mechanism was also proposed to elucidate the role of carbon spheres in the CuO-BVO@C composite as a photocatalyst for degradation of organic pollutants.