Hierarchical Bi2WO6/BiFeWO6 n-n heterojunction as an efficient photocatalyst for water splitting under visible light

A hierarchical Bi2WO6/BiFeWO6 architectures were synthesized by a facile and low-cost hydrothermal approach using Bi2WO6 flower structure as an efficient backbone for the growth of layered BiFeWO6 sheets. The conduction band offset and bandgap of flower like Bi2WO6 were tailored strategically as active photocatalyst under visible light and suitable for water reduction. By developing n-n heterojunction between Bi2WO6 and BiFeWO6, the active surface area as well as number of free charge carriers have been enhanced which may boost the catalytic redox reactions. The physicochemical properties of the heterojunction was characterized to investigate the phase, morphology, thermal stability, light absorption and oxidation states of the elements. The photocatalytic activity of Bi2WO6/BiFeWO6 heterojunction was investigated through H2 generation via water splitting under visible light, where four-fold enhanced activity achieved for heterojunction compared to bare Bi2WO6. Further, photoelectrochemical properties were studied to determine the band edge potentials and illustrate the enhanced photoresponse for heterojunction. The Bi2WO6/BiFeWO6 heterojunction showed lower charge transfer resistance compared to Bi2WO6, owing to efficient charge separation at electrode-electrolyte interface. The synergistic effect of high surface area, lower recombination rate and the suitable band edge potentials led to high catalytic activity, good cycling stability and superior photoelectrochemical response of heterojunction. This work provide insight into the synergistic effect of hierarchical n-n heterojunction and opens up an avenue for rational design of photocatalyst for water splitting and H2 generation.