N. R. Srinivasan's Talk

Jul 24, 2014 - 17:00

Jul 24, 2014 - 18:00

Room 118 Creativity Hall Chemical Engineering

Seminars

N. R. Srinivasan Ph D Student IITB

Abstract : Nanoparticles are generally embedded inside the pores of porous solid to prevent their aggregation in order to achieve better performance in catalysis water treatment etc. The present work aims to show that nanoparticles need not be embedded only inside the pores but can also be embedded in different regions of porous solid (in-between the pores or on the external surface of solid etc.) to enhance the reactivity in diffusion-adsorption-reaction systems. The reactivity enhancement is not only based on the location of particles in the porous solid but also on the structural features of the latter. With this objective I will discuss about photocatalytic degradation of dye by semiconductor nanoparticle (SnO2 TiO2 and SnxTi1-xO2) - mesoporous silica (SBA-15) hybrid in the first part of the talk where nanoparticles are embedded inside the hydrophilic SBA-15 without pore blockage. We find that obtained first order rate constant (K = 0.031 min-1) by Sn0.05Ti0.95O2-SBA-15 is more than ten times and five times of only SnO2 and only TiO2 nanoparticles respectively. Next I will discuss about SnO2-CMK-5 in the second part of talk where SnO2 nanoparticles are embedded in-between the mesopores of the hydrophobic CMK-5 and tested for its reactivity against lithium-ion in lithium-ion battery. The diffusion coefficient of the Li+ ion inside SnO2-CMK-5 (1.1 × 10-13 cm2 s-1) is two orders of magnitude larger than that of only bare SnO2 electrodes (8.5 × 10-15 cm2 s-1). As a result the specific capacity by SnO2-CMK-5 is 598 mA h g-1 at a current density of 178 mA g-1 after 30 cycles which is much higher than that of only SnO2 (42 mA h g-1) or only CMK-5 (218 mA h g-1) electrodes. Finally to show the benefit of particle location on the external surface of a porous solid a strategy to selectively attach more Ag nanoparticles on the external surface of activated carbon was developed to increase the death rate of E.coli. This shows an order of magnitude increase in death rate constant from 3.72 to 41.88 h−1. These three studies thus show the importance of selective embedding of nanoparticles on a mesoporous solid to enhance their reactivity by considering the advantage of different templating and surface functionalization strategies for optimum benefit as per the needs of the application whether photocatalysis energy storage device or water treatment.