Fast interfacial charge transfer in α-Fe2O3-δCδ/FeVO4-x+δCx-δ@C bulk heterojunctions with controllable phase content.

ABSTRACT

The novelties in this paper are embodied in the fast interfacial charge transfer in α-Fe2O3-δCδ/FeVO4-x+δCx-δ@C bulk heterojunctions with controllable phase compositions. The carbon source-glucose plays an important role as the connecting bridge between the micelles in the solution, forming interfacial C-O, C-O-Fe and O-Fe-C bonds through dehydration and polymerization reactions. Then the extra VO3- around the FeVO4 colloidal particles can react with unstable Fe(OH)3, resulting the phase transformation from α-Fe2O3 (47.99-7.16%) into FeVO4 (52.01-92.84%), promoting photocarriers' generation capacities. After final carbonization, a part of C atoms enter into lattices of α-Fe2O3 and FeVO4, forming impurity levels and oxygen vacancies to increase effective light absorptions. Another part of C sources turn into interfacial carbon layers to bring fast charge transfer by decreasing the charge transition resistance (from 53.15 kΩ into 8.29 kΩ) and the surface recombination rate (from 64.07% into 7.59%). The results show that the bulk heterojunction with 90.29% FeVO4 and 9.71% α-Fe2O3 shows ideal light absorption, carriers' transfer efficiency and available photocatalytic property. In general, the synergistic effect of optimized heterojunction structure, carbon replacing and the interface carbon layers are critical to develop great potential in stable and recoverable use.