In-situ growth P-N heterojunction composite photocatalyst enhanced visible-light-driven photocatalytic performance

Improving the extraction and separation rate of electron-hole couple in photocatalysis is one of the key technologies to improve the catalytic performance of photocatalysts. Flower-like g-C3N4/BiOBr positive and negative (P-N) heterojunction composite were prepared by in-situ method using graphite phase carbon nitride as basic dopant, which was obtained by stripping bulk carbon nitride with concentrated sulfuric acid. The effect of pH value on morphology of g-C3N4/BiOBr composite was studied. Crystal structure, morphology and composition properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy disperse spectroscopy (EDS), transmission electron microscope(TEM), ultraviolet-visible(Uv-vis) and specific surface area(BET). The results show that heterojunction is established between g-C3N4 [002] facets and BiOBr [001] facets inside g-C3N4/BiOBr composites, accelerating the collect and separation of the photo induced electron(e)-hole(h) pairs. Graphite phase carbon nitride reduces the band gap width of g-C3N4/BiOBr composites to 2.71 eV, compared with BiOBr to 2.75 eV, which can expand the light absorption range. Beside, the specific surface area of BiOBr and g-C3N4/BiOBr are 1.27 m(2)/g and 6.43 m(2)/g, which means increased reactive side. The photocatalytic activity of g-C3N4/BiOBr composite is better than pure g-C3N4 and BiOBr, which also shows high efficiency when reused. g-C3N4/BiOBr composite has best photocatalytic performance with pH = 8, its degradation rate of orange yellow G, rhodamine B and methyl orange are 91.00%, 95.51% and 96.72%, respectively.