Flow chemistry presents an appealing approach to increase the scalability of nanoparticle (NP) synthesis and catalytic applications. Herein, we applied microwave heating (µwI) coupled with single-phase-continuous-flow, and double-phase-microfluidic droplet-flow methods for the synthesis of Rh NPs. Using the single-, and double-phase flow methods, monodispersed Rh NPs could be successfully synthesized at lower reaction temperature of 120 °C in reaction times as short as 5 and 6 minutes respectively. While single-phase flow methods resulted in time-dependent size-tunable thermodynamically stable cuboctahedral geometries of Rh NPs, double-phase flow methods yielded kinetically stable multipod Rh nanostructures in comparable yields (statistical occurrence ≥ 90%). Increasing reaction time and temperature in double-phase flow methods led to a systematic decrease in average appendage length of the Rh multipod NPs. This observation along with a much smaller statistical occurrence of 50% for Rh multipods synthesized at 150 °C in 30 minutes indicated toward Rh multipods being kinetically favored nanostructures. Conventional oil-bath heating (CvH) didn’t only led to statistically smaller % of Rh multipods but also these NPs were thermally less stable. A comparative gas-phase cyclohexene hydrogenation study using Rh multipod NPs showed that these multipods are catalytically more active than their cuboctahedral counterparts. Rh multipod NPs presented a higher exposed surface fraction of catalytically active sites and also had more favorable rate-limiting steps associated with them. In a separate study, we are currently studying synthesis and catalytic applications of Cu containing bimetallic NPs. Besides, significantly driving down the cost of precious metal-based catalysts, Cu incorporation to Rh, & Pd presents an attractive opportunity for origination of synergistic phenomena between the two constituent metals occuring at nanoscale. A wide compositions of size and shape tunable RhCu and PdCu bimetallic NPs can be successfully synthesized under µwI. Heterogeneous catalysts loaded with these RhxCu100-x and PdxCu100-x NPs have been synthesized and are being tested for gas-phase cyclohexene hydrogenation and solution-phase nitrite reduction reactions. We also intend to combine our experimental study of Cu containing bimetallic NPs with theoretical calculations (via DFT) in order to better understand the stability and catalytic properties of such hybrid NP systems.

Synthesis and catalytic applications of Rh multipod nanoparticles using flow methods and CuM, (M=Rh, Pd) bimetallic nanoparticles in batch reactors under microwave heating

256th National Meeting (2018)

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