Eco-Friendly Coffee Waste-Based Carbon Dots Coupled to ZnBi-Layered Double Hydroxide Heterojunction: Enhanced Control of Interfacial Charge Transfer for Highly Efficient Visible-Light Catalytic Activity

Figure 4

XPS spectra of (a) C 1s, (b) Zn 2p, (c) Bi 4f, and (d) O 2s in according to ZnBi₂O₄ and CDs (2%)-ZnBi₂O₄.

(a)

(b)

(c)

(d)