Facile green synthesis of magnetically separable Au–Pt@TiO2 nanocomposite for efficient catalytic reduction of organic pollutants and selective oxidation of glycerol

Abstract

Magnetically separable monometallic and bimetallic Au and Pt NPs anchored on TiO2 nanocomposite were prepared using dahlia flower extract through a greener approach. The prepared nanoparticles (NPs) act as an efficient active metal-based catalyst for glycerol oxidation reaction (GOR) and organic compounds reduction reaction (ORR). The phytochemicals present in dahlia flower extract acts as reducing and stabilizing agent for the development of metal NPs on TiO2 surface. For bimetallic (Fe3O4@TiO2–AuPt) NPs, the conversion efficiency for GOR was found to be 2-fold higher than those of monometallic NPs. The products of GOR over magnetically separable monometallic and bimetallic catalysts were analyzed by HPLC and products such as formic acid (FA), glycolic acid (GCA), glyceric acid (GLA), and tartronic acid (TA) were detected. In addition, ORR of 4-nitrophenol (4-NP), methylene blue (MB) and congo red (CR) in the existence of sodium borohydride (NaBH4) were studied. It was found that the reduction reactions were completed within a few seconds for mono- and bimetallic nanocomposites. Comparatively, Fe3O4@TiO2–AuPt nanocomposite showed much higher efficacy (8, 6 and 5 s) for 4-NP, MB and CR reduction along with very good stable catalytic activity (∼98%) after six cycles. We hypothesize that the improved yield in GOR and faster reduction in ORR by Fe3O4@TiO2–AuPt nanocomposites are related to the synergistic effect of metal alloy formation and support materials.