Facile strategy of synthesizing α-MoO3−x nanorods boosted as traced by 1% graphene oxide: Efficient visible light photocatalysis and gas sensing applications

Herein, we report the synthesis of MoO3−x nanorods via an environmentally solvothermal/annealing route, which involves refluxing of an ethanolic solution of (NH4)6Mo7O24.4H2O for 5 h at 70 °C followed by drying and calcination at 350 °C for 2 h. Graphene oxide (GO) incorporation at 1% ratio into MoO3 increases the oxygen deficient ratio (20.6%) compared to GO free MoO3 catalyst (17.3%), as emphasized by XPS results. A comprehensive characterization using XRD, TEM-SAED, UV–vis, FTIR, Raman, photoluminescence and N2 sorptiometry was illustrated. The irregular circular shape of 1%GO.MoO3−x; of Eg equal 2.7 eV, and an average diameter of 40 nm has shown higher photocatalytic action towards MB degradation (20 ppm) under visible light illumination (160 W, >420 nm) giving a rate constant of 0.016 min−1 exceeding that of MoO3−x by 18 times. Although 1%GO.MoO3−x exhibits lower surface area and pore volume than those in GO free MoO3−x, the potentiality of the former is mainly dependent on the strong linkage formed between MoO3−x and graphene sheets. Based on increasing the oxygen deficiency in 1%GO.MoO3−x, powerful oxidizing moieties are depicted to affect the MB degradation including in situ generated H2O2, O2¯ and O H species. The gas sensing property of 1%GO.MoO3−x towards 100 ppm NH3 at 200 °C was increased by 6.4 times that of GO free MoO3−x nanorods. This was mainly due to the hetero-junction formed between n-(MoO3−x) and p-type (partially reduced GO) conducting channels; affirmed via Mott-schottky plot, and the facile electron transfer from GO into MoO3−x. The mechanism of the oxygen deficit 1%GO.MoO3−x structure is also discussed, exploring that this type of sensor has a promising application to other reducing gases. The 1%GO.MoO3−x sensor exhibited long-term stability at different NH3 concentrations as well as high selectivity exceeding the corresponding pure counterparts.