(583ba) Development of a Reverse Micelle Catalyst Synthesis Method for Producing Multi-Metal Nano-Structures On a TiO2 Anatase Support

Since the beginning of heterogeneous catalysis in the early half of the last century, finding new methods of creating specific sizes and shapes of metallic structures on solid support materials has been at the forefront of catalysis science.  For decades incipient wetness techniques, with aggregate sizes in the micrometer range, have dominated the market, especially with the addition of promoter metals during the preparation procedure.  However, many unique catalytic reactions can be possible only with nano-sized metal and metalloid structures on the support material.  It has been well documented that support materials often play a role in the reaction sequence and not just a means of providing optimum surface areas.

            In this work, NiSn nanoparticles were prepared using reverse micelle method. Reverse micelles were used to improve the nanoparticle size uniformity of Ni and NiSn combinations supported on TiO₂ (anatase), which has an abundance of oxygen vacancies within its lattice structure. The intent with the NiSn-TiO2 catalyst was to convert CO2 in trireforming reactions. In the reverse micelle preparation, all the steps were carried out under inert atmosphere to exclude oxygen from oxidizing the metals before deposition onto the TiO2. Two microemulsions, containing metal nitrate (Ni(NO₃)₂ and Sn(NO₃)₂) and reducing agent sodium borohydride (NaBH₄) were mixed together with rigorous stirring to produce the Ni nanoparticles.

            Completed catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray microanalysis (SEM/EDX) and transmission electron microscope (TEM). Temperature programmed desorption (TPD) of CO and CO₂ were performed to test the catalytic activity of the catalysts. Raman and FTIR spectroscopy were utilized to understand the effects of different metal concentrations on the Ti-O band. These findings and possible catalytic reaction mechanisms will be presented.