The comparative study of two reusable phosphotungstic acid salts/reduced graphene oxides composites with enhanced photocatalytic activity

In this work, two recyclable phosphotungstic acid salts/reduced graphene oxides were successfully prepared. The prepared samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), Raman spectroscopy, and photoluminescence spectroscopy (PL). The structure and catalytic performance of two composites were comparatively investigated, and the reduced graphene oxide mass ratios in K3[PW12O40]/reduced graphene oxide (denoted as KPW-RGO) and (NH4)3[PW12O40]/reduced graphene oxide (denoted as NH4PW-RGO) were optimized and their roles in them were explored. The results indicate that the Keggin structures of KPW and NH4PW are still kept after being anchored on the RGO surface, but their morphologies change a lot in composites. The photocatalytic activities of KPW-3RGO (0.01989 min-1) are 5.42 times than that of KPW (0.00367 min-1), and NH4PW-1RGO (0.0184 min-1) is 2.26 times than that of NH4PW (0.00814 min-1). The enhanced photocatalytic activity is mainly ascribed to photo-induced interfacial charge transfer on the heterojunction between RGO and NH4PW or KPW and strong adsorption ability of RGO towards MO. Moreover, NH4PW-1RGO and KPW-3RGO had much better photocatalytic activity, good recyclable ability, and stability compared to HPW-RGO, which cannot be recycled.