Projects

 

(i) Encapsulation of metal nanoparticles within mesoporous silica

(ii) Ultra small metal nanoclusters encapsulated within silica nanospheres

(iii) Development of noble metal incorporated structured oxides for Water Gas Shift reaction for hydrogen production.

(iv) Dense ceramic membranes for oxygen enrichment in coal combustion processes.

(v) Photocatalytic water splitting

 

 

(i) Encapsulation of metal nanoparticles within mesoporous silica

Dr. Atul Prashar (now in Dow Chemicals Pune)
Ms. Sumona Ghosh (now in SABIC, Baroda)

Current methods of supporting metal NPs into mesoporous oxides have the disadvantage of uncontrolled growth of metal particles on the walls since no preventive measures are taken to ensure that the metal precursors are isolated within the channels. In our attempts to have better control over the size, amount and location of Pt particles in SBA-15, we have developed a simple and convenient truly in-situ one pot method of dispersing the metal salt precursors within template polymers modified with ionic surfactants in a controlled manner. The ionic surfactants are expected to be dispersed within the polymer micelle structure with the ionic head groups decorating the corona and the hydrophobic tail groups penetrating the core. Added to this polymer-surfactant composite, metal precursor ions diffuse into the corona depending on various factors viz. ageing time, surfactant and precursor concentration etc. Later calcination of this material leads to a dispersion of metal nanoparticles of fairly uniform size distribution.


This method also provides an easy and versatile way to have an enhanced control over fine tuning of the particle sizes and shape by simple tweaking of synthetic conditions. Particle size effect on hydrogenation and oxidation also are of interest to us. This method could be translated into isolating ultra small oxide clusters like CeO2 within the mesoporous channels.

 

 

 

 

 (ii) Ultra small metal nanoclusters encapsulated within silica nanospheres

Mr. Anupam Samanta (SRF)

Ultra small nanoclusters have molecular properties compared to metal nanoparticles which is evident from their optical properties. We have synthesised new Au cluster with sizes < 2 nm and encapsulated them in silica nanospheres of size ~ 30 nm. These systems have immense applications in cell imaging and catalysis.

 

 

 

 

(iii) Development of noble metal incorporated structured oxides for Water Gas Shift reaction for hydrogen production.

Mr. T. Rajesh (SRF)

Urgency of identifying a renewable and alternate source of energy hardly needs emphasizing and hydrogen is projected as one such source. Till such a process which produces hydrogen from sustainable sources efficiently can be developed, available sources like natural gas need to be reformed into hydrogen. Water Gas Shift (WGS) reaction is an important component of fuel processing which not only reduces the concentration of poisonous CO but also enriches the feed with H2 by using water. Noble metal catalysts are found to be most suitable for WGS in small scale fuel processors, however, agglomeration of active metal particles and subsequent deactivation has been a challenging problem faced by the community. We have looked at the problem with the aim of isolating active centers in lattice points thereby avoiding coalescence and have developed ceria based perovskites with noble metals incorporated in the lattice sites. These materials are found to be highly active as well as stable on stream.

 

 

 

 

(iv) Dense ceramic membranes for oxygen enrichment in coal combustion processes

Mr. C.P. Jijil (PAIII)  

Currently most of the countries including China and India are looking to use the natural resource abundantly available to them viz., coal, to meet electricity and heating needs. However, environmental impacts of widespread use of coal burners and thermal power stations will be enormous. Most impactful pollutants are from the flue gas, like COx, NOx, SOx etc which have very bad effects on health and environment. The only way this can be addressed is to use efficient combustion and post-combustion capture techniques. When air is used as the oxidant, which is the case normally, N2 not only dilutes the oxidant stream but also produces NOx pollutants. This can be avoided by using pure oxygen which not only enhances the efficiency of combustion but also eliminates N2 in the feed thereby preventing NOx in the flue gas. Dense ceramic membranes which conduct oxide ions under concentration gradient is a potential solution to this problem. The pre-requisites for the materials to be used for such membranes are good oxygen permeance and ease of fabrication and most importantly stability under reducing and oxidising conditions. We are developing novel materials in perovskite and related structure types. Their electrochemical as well as structural characteristics are followed.

 

 

 

 

(v) Photocatalytic water splitting

Ms. Leena George (PAIII) and Ms. Soumya B.N (JRF)

Urgency of identifying a renewable and alternate source of energy hardly needs emphasizing and hydrogen is projected as one such source. With more than 100000 TW of solar energy falling on earth and 70% of earth’s surface being covered by water, a process which combines these two sources will be ideal for future energy directions. There are two possible ways of utilising solar energy, for direct electricity generation as in photovoltaic cells or generation of fuels or chemicals as in photosynthesis. For generation of H2 from water, we have to move more towards the principles of photosynthesis where the catalytic centre is involved in a one electron transfer. Nature has taken precautions to prevent recombination and energy wastage by spatial separation between the hole and the electron. Abiding by nature’s principles, we are looking for materials which conforms to the following three points; (i) sunlight is absorbed by the catalyst efficiently so that electrons are excited to the conduction bands and holes are created in the valence band (ii) these electrons and holes are spatially separated to prevent recombination which will lead to heat formation and wastage of energy (iii) the excited electron can be transferred to do useful work - splitting of water into H2 and O2.