Figure 3. SEM images of (a) Co₃O₄-0.0625 on FTO and (b) CoS-0.0625 on FTO; (a-1) and (b-1) are SEM images at 150,000×, (a-2) and (b-2) are SEM images at 30,000× magnification, (a-3), (a-4), (b3), and (b-4) are element mapping results of Co, O, and S.