Monoclinic dibismuth tetraoxide: A new visible-light-driven photocatalyst for environmental remediation

A new visible-light-driven photocatalyst , monoclinic dibismuth tetraoxide (m-Bi 2 O 4 ), has been discovered. This simple oxide with mixed valent states (Bi 3+ and Bi 5+ ) has a band gap energy of 2.0   eV, and is responsive to wavelength up to 620   nm. The first-principle calculations within the hybrid density functional framework (HSE) indicate that m-Bi 2 O 4 is a typical indirect-gap semiconductor. It shows much higher photocatalytic degradation activity as well as photostability than some of the well-investigated highly efficient photocatalysts, such as CdS and Bi 2 O 3 . Not only typical dyes and colorless aromatic compounds, including rhodamine B, methyl orange, methyl blue, phenol and 4-nitrophenol, but also bacterial ( Escherichia coli ) cells can be effectively degraded/inactivated in the presence of m-Bi 2 O 4 . The electronic potential of band structure is studied and a photocatalytic mechanism is also proposed, in which both OH and direct h + oxidation play important roles in the degradation process. Our discovery highlights the potential of developing Bi 2 O 4 -based photocatalysts as a new class of highly active, stable and safe photocatalyst for versatile pollutant degradation and disinfection under visible light .