Lab Chip (2012)

Credit: © RSC 2012

Ning Wang and co-workers from China and Switzerland have recently shown how to reduce one of the performance limitations of photoelectrocatalytic reactors: unwanted recombination of photoexcited electrons and holes. Previous work had shown that a carefully designed combination of optics and microfluidics can help overcome mass and photon transfer limits, by increasing surface-area-to-volume ratios and allowing direct delivery of light to reaction surfaces. However, these 'microreactors' still have a low photonic efficiency and one main reason is the recombination of photoexcited electrons and holes. To prevent this, Wang and colleagues introduce an external bias electric field that forces separation of the electrons and holes. Their microfluidic photoelectrocatalytic reactor (10 mm × 10 mm × 0.1 mm) is made from a blank indium tin oxide glass substrate, an epoxy spacer and a BiVO4-coated indium tin oxide glass substrate illuminated by a blue light-emitting diode panel (10 mm × 10 mm). These reactors should be scalable, and the team hopes that they will be of interest for applications such as water and air purification, the photoreduction of CO2 and heavy metal ions, and artificial photosynthesis.