Enhanced photocatalytic performance of CuFeO2-ZnO heterostructures for methylene blue degradation under sunlight

One of the strategies to overcome the drawbacks of fast charge recombination of a photocatalyst is to develop semiconductor heterostructures. Herein, we report a two-step precipitation-hydrothermal process to create CuFeO2-ZnO heterostructures with different weight percentages of CuFeO2 (0.5, 1, 5, and 10%). Though X-ray diffraction detected the presence of CuFeO2 on ZnO above 5%, Raman spectroscopy could reveal the presence of CuFeO2 phase as low as 0.5 wt%. For all of the compositions, the bandgap of ZnO did not vary (3.15 eV) on forming heterostructures with CuFeO2. The oxidation of methylene blue under sunlight was used to determine the photocatalytic performance of the heterostructures. In comparison to pure ZnO and CuFeO2, CuFeO2-ZnO heterostructures exhibited a better photocatalytic efficiency. Overall, 5 wt% CuFeO2 on ZnO showed 100% degradation with a rate constant of 0.272 +/- 0.002 min(-1), which is 16 times faster than ZnO. Time-resolved photoluminescence analysis indicated a higher lifespan of charge carriers in the 5wt% CuFeO2-ZnO heterostructure (32.3 ns) than that of CuFeO2 (0.85 ns) and ZnO (27.6 ns). The Mott-Schottky flat band potentials of ZnO and CuFeO2 was determined to be -0.82 and 1.17 eV, respectively, revealing the presence of Type I heterostructures. The heterostructures also showed outstanding recyclability, with a degradation rate of 97% even after four cycles. The current study shows the significance of forming p-type CuFeO2 and n-type ZnO heterostructures for enhanced photocatalysis.