A new bismuth potassium nitrate oxide, Bi1.7K0.9O2(NO3)2: Synthesis, structure, thermal behavior, and photocatalytic properties

We report here the first observation of a bismuth potassium nitrate Bi1.7K0.9O2(NO3)2, obtained via thermal decomposition of bismuth and potassium nitrate mixtures. The new compound is orthorhombic, space group Immm (71), Z = 2, with a = 3.8698(7) Å, b = 3.8703(7) Å, and c = 24.1271(4) Å. Its crystal structure was refined from powder X-ray diffraction data by analogy with the mineral beyerite, Bi2O2Ca(CO3)2. The morphology and elemental composition of Bi1.7K0.9O2(NO3)2 were characterized using scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS). Its phase transformations upon heating and products of its thermal decomposition were studied using XRD, TGA and FTIR. At 440 °C, Bi1.7K0.9O2(NO3)2 transforms to another basic bismuth potassium nitrate with demonstrates a very similar XRD pattern but slightly larger cell parameters. At 520 °C, the intermediate oxide nitrate decomposes into a mixture of crystalline α-Bi2O3 and KNO3. The as prepared Bi1.7K0.9O2(NO3)2 showed lower than TiO2 (Degussa P25) photocatalytic activity upon decomposition of a widely used model pollutant, Rhodamine B (RhB) and photooxidation of potassium iodide under UV–vis light irradiation. Interaction with potassium iodide in alkaline media resulted in formation of Bi5O7I.

New Bi1.7K0.9(NO3)2O2 phase was synthesized and its structure was refined from powder XRD data. SEM, XRD, FTIR and TGA investigations of the new phase and the products of its thermal decomposition were performed and photocatalytic properties were examined.Figure optionsDownload as PowerPoint slideHighlights
► New Bi1.7K0.9(NO3)2O2 phase was synthesized by thermal method.
► Structure was refined from powder X-ray data using Rietveld procedure.
► The new material and products of its thermal decomposition have been studied using XRD, TGA and FTIR methods.
► Photocatalytic properties were studied using Rhodamine B and KI.