Carbon microspheres work as an electron bridge for degrading high concentration MB in CoFe2O4@carbon microsphere/g-C3N4 with a hierarchical sandwich-structure

A high efficiency photocatalyst CoFe2O4@porous carbon microspheres/g-C3N4 (Co@PC/CN) with sandwich-structure has been fabricated to degrade 500 mg/L methylene blue (MB). The unique combination and sandwich layered structure of Co@PC/CN result in an excellent degradation efficiency (99%). The sandwich layered structure provides more dense active sites and higher efficient light harvesting. More importantly, the porous carbon microspheres inhibit the recombination rate of photo-generated carriers, and avoid the contact of g-C3N4 and CoFe2O4 to change the transfer pathway of electrons. Moreover, the Co@PC/CN can simultaneously retain photo-reduction (reducing O-2 to center dot O-2(-)) and photo-oxidation (producing center dot OH by CoFe2O4) properties in photo-catalysis, which degrades 500 mg/L MB by center dot O-2(-), center dot OH and h(+). This strategy of composite photocatalysts with the sandwich layered structure provides a reasonable design concept for improving the photocatalytic efficiency of g-C3N4.