Fig. 1. The photocurrent comparison of pure Co₃O₄ thin films and Co₃O₄/G thin films with different doping ratios

Fig. 2. FESEM images of pure Co₃O₄ films^［30］ and Co₃O₄/G（Co/G=1∶2）films at different magnifications

Fig. 3. Raman spectra of Co₃O₄/G thin film samples

Fig. 4. The photocurrent comparison of Co₃O4@BiVO₄ composite film and（Co/G is 1∶0.5，1∶1，1∶2，1∶3）@BiVO₄ composite film samples

Fig. 5. FESEM images of（Co₃O₄/G）@BiVO₄ composite films at different multiples and EDS energy spectrum and surface scan images

Fig. 6. The TEM and HRTEM images of（Co₃O₄/G）@BiVO₄ composite films and the original image of morphology change

Fig. 7. XRD patterns of Co₃O₄ films^［30］，Co₃O₄/G films and（Co₃O₄/G）@BiVO₄ composite films

Fig. 8. XPS spectra of（Co₃O₄/G）@BiVO₄ composite films

Fig. 9. Optical absorption and optical band gap of Co₃O₄ film^［30］，Co₃O₄/G film，Co₃O₄@BiVO₄ composite film^［30］ and（Co₃O₄/G1∶2）@BiVO₄ composite film