Built-in electric field-assisted charge separation over carbon dots-modified Bi2WO6 nanoplates for photodegradation

Bi2WO6 photocatalyst has attracted much interest but suffers from easy recombination of electron-hole pairs. Herein carbon dots (CDs) as a cocatalyst were hydrothermally hybridized with Bi2WO6 nanoplates with aim of efficient separation of charge carriers. Electron transfer from CDs to Bi2WO6 across their interfaces upon contact was revealed by XPS results and further supported by differential charge density analyses. Such electron transfer led to a built-in electric field pointing from CDs to Bi2WO6, which drove photoinduced electrons flowing to CDs under light irradiation. DFT simulation showed the introduced electron was mainly distributed on CDs instead of Bi2WO6, which implied that CDs had impressive capability of taking photoinduced electrons under irradiation. Such efficient charge separation was experimentally supported by photoelectrochemical analyses. The superoxide radicals and holes were found to participate in the photodegradation of RhB under visible light irradiation. The enhanced photocatalytic activity of CDs/Bi2WO6 could be ascribed to the efficient charge separation and large specific area of Bi2WO6 nanoplates.