Fabrication of a magnetic retrievable dual Z-scheme g-C3N4/BiVO4/CoFe2O4 composite photocatalyst with significantly enhanced activity for the degradation of rhodamine B and hydrogen evolution under visible light

Abstract

The magnetic dual Z-scheme composite photocatalyst g-C3N4/BiVO4/CoFe2O4 was successfully fabricated via a high-temperature solid-state route. The photocatalytic activity of the as-prepared composites was evaluated by detecting the variation in rhodamine B (RhB) concentration under visible light irradiation. The results show that the composite exhibits much higher photocatalytic activity than bare g-C3N4, bare BiVO4 or the binary composite of g-C3N4/BiVO4, and that the degradation efficiency of RhB can reach 94.5% within 100 min. The trapping experiments indicate that all three radicals ·OH, ·O2− and h+ contribute to the photocatalytic degradation of RhB, and that ·OH radicals play the most important role, followed by superoxide anion ·O2− radicals and finally by holes h+. The hole scavenger EDTA shows a positive influence on the photocatalytic degradation of RhB; it only takes 30 min to degrade 99.6% of RhB, which is nearly 3.5 times faster than that without EDTA. Moreover, the cycle tests prove that the as-prepared composite photocatalyst has good stability and reusability; after 10 consecutive cycles, no obvious deactivation was observed. It also shows excellent performance in water splitting for hydrogen evolution with overpotential values of −155 mV at a current density of 10 mA cm−2.