Role of reduced graphene oxide in boosting visible-light-driven photocatalytic activity of BiVO4 nanostructures

Abstract

Although monoclinic scheelite bismuth vanadate (m-BiVO4) is a promising photocatalyst due to its low band gap (Eg = 2.4-2.6 eV), significant visible light absorption, and its valence band potential is positive enough for water splitting and pollutants degradation, it has some drawbacks hindering its sole usage in photocatalysis. These drawbacks include low surface conductivity, fast electron-hole (e-/h+) pair recombination, low surface area, and low solubility in the aqueous medium. Therefore, m-BiVO4 is composited with reduced graphene oxide (r-GO) to mitigate these drawbacks. r-GO has an extremely large surface area, a high electrical conductivity and can accept and trap electrons from m-BiVO4 via its delocalized conjugated 𝜋-system. Such traps lengthen the electron / hole (e-/h+) pair lifetime on m-BiVO4 increasing the photocatalytic reactions efficiency on its surface. In addition, the presence of oxygen-containing groups on r-GO helps in anchoring m-BiVO4 particles on the r-GO layer so the m-BiVO4 particles are more dispersed and display a larger surface area. These oxygenated groups ease the solubilization of anchored m-BiVO4 particles in water by forming hydrogen bonds. In this mini-review, m-BiVO4–r-GO composite applications in photocatalytic water splitting, pollutants degradation, and other reactions will be briefly discussed. Generally, these composites showed remarkable results in reactions that rely on the valence band holes of m-BiVO4, whereas the reactions that depend on conduction band electrons required morphology and size modification for the m-BiVO4 before its compositing with r-GO.