Mechanochemically synthesized CuO/m-BiVO₄ composite with enhanced photoelectrochemical and photocatalytic properties

The present work aims to prepare a CuO/monoclinic-BiVO₄ (m-BiVO₄) composite with large surface area for enhanced photocatalytic performance. Nano-sized m-BiVO₄ photocatalysts with a large BET surface area (10 m² g^-1) were first synthesized by a mechanochemical high energy ball milling approach. To further improve the photo-efficiency, 2-10 at% of a p-type CuO co-catalyst was introduced to the surface of BiVO₄ by impregnation to constitute the heterostructured composite. The physicochemical properties of the as-prepared composite were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence and surface photovoltage responses. The composite exhibited much higher photocurrents in photoelectrochemical (PEC) tests and faster photocatalytic degradation of rhodamine B upon visible light irradiation in comparison with pristine BiVO₄, appearing as a promising visible light active photocatalyst suitable for environmental remediation. The improved PEC and photocatalytic properties can be attributed to the simultaneous enhancement on photon absorption and charge separation. The band structure and possible charge transfer process of the CuO/BiVO₄ composite were also elucidated to explain the enhanced photo-activities.