The preparation and characterization of CaMg(CO3)2@Ag2CO3/Ag2S/NCQD nanocomposites and their photocatalytic performance in phenol degradation

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Using CaMg(CO3)2 as hard template, CaMg(CO3)2@Ag2CO3 microspheres were first obtained via a fast cation exchange process. Then, CaMg(CO3)2@Ag2CO3/Ag2S was fabricated by further anion exchange. Finally, trace nitrogen-doped carbon quantum dots (NCQDs) were coupled into CaMg(CO3)2@Ag2CO3/Ag2S and obtained CaMg (CO3)2@Ag2CO3/Ag2S/NCQD nanocomposites (< 380 nm). Different characterization techniques, e.g., XRD, N2 physical adsorption, SEM, TEM, UV-vis, FT-IR, X-ray photoelectron spectroscopy, TPR, photoluminescence, and electrochemical impedance spectroscopy test, were applied to investigate the physicochemical property of the as-prepared samples. The photocatalytic properties were evaluated by phenol degradation under simulated sunlight illumination. The results demonstrated that with a very low content of Ag2CO3 (0.67 wt%) and Ag2S (1.72 wt%) and a trace of NCQDs (0.46 at.%), the CaMg(CO3)2@Ag2CO3/Ag2S/NCQD nanocomposites exhibited excellent activity and stability for phenol degradation. The reasons for the enhancement of photocatalytic activity and stability are due to that the coexistence of trace Ag2S and NCQDs can effectively improve the texture property of photocatalyst and effectively promote the separation of photogenerated electrons and holes, resulting in more radicals (h+ and·O2−) to destroy the phenol. This work provided a new method to develop low-cost Ag-based semiconductor photocatalysts for environmental remediation.