Figure 3. SEM images: (a) Cu-MOFs; (b)ZIF-9(Co); (c) Cu-Co-2; (d)Cu-P; (e)Co-P and (f) Cu-Co-2P-2.
Cu-Co-2P-2 composite photocatalyst was tested by TEM characterization to further understand the morphology and microstructure of the catalyst. Figure 4(a) and Figure S2(a, b) show the TEM images of Cu-Co-2P-2 composites at different magnifications, respectively. The results showed that Cu-P-2 and broken Cu-MOFs skeletons existed in the Cu-Co-2P-2 sample when Cu-MOFs was not completely phosphated, and obvious transparent sheet-like Co-P appeared on the edges [30]. In addition, the HRTEM image of the Cu-Co-2P-2 composite is shown in Figure 4(b). Cu-MOFs is perfectly combined with Co-MOFs phosphatium phospholipids, and the lattice fringes of Cu3P and CoP can be observed. The lattice spacings of 0.25 nm and 0.24 nm correspond to the (112) and (111) crystal planes of Cu3P and CoP, respectively. The existence of Cu (200) crystal plane can be also observed, and its lattice spacing is 0.18 nm. EDX results show that Cu-Co-2P-2 composites contain Cu, Co and P elements (Figure 4(c)). According to XRD analysis, it can be seen that Cu-Co-2P-2 composites obtained after phosphating of Cu-Co-2 samples mainly exist in the form of Cu3P and CoP. At the same time, the electron diffraction (SAED) pattern of Cu-Co-2P-2 (Figure 4(d)) shows the relatively high crystalline characteristics of the composite sample. Figure 4(e) is a map of Cu-Co-2P-2, in which the elements of Cu, Co, and P are evenly distributed. This shows that the phosphating of Cu-MOFs@ZIF-9(Co) was successful.