(66d) Engineered Nanomaterials for Environmental and Energy Related Applications

The continuing, rapid worldwide progress in material science and catalysis   promises  “innovative &cutting edge processes”  for improving quality of life and increasing the efficiency of harvesting and utilizing energy resources.Thus to  ensure  nation’s economic competitiveness catalytic chemistry is proving to be an essential prime requisite for  making  cleaner environment  a reality and  enhancing sustainability and carbon balance. In order to meet the challenges of these research areas, engineered nanomaterials and  biocatalysts  are being developed for  environmental remediation and hybrid energy systems with novel cross-disciplinary paradigm. Also the tool of biocatalysis is being used for re-engineering and biomimicking the natural processes, preferably, in nature’s way. In this connection, wide array of materials  including engineered bio-polymers,  stabilized enzyme nanoparticles  are being synthesized for  applications like i) Simultaneous carbon capture  and sequestration and ii)CO₂capture and valorization.  

i) Simulataneous carbon capture ,valorization and sequestration : CA  as ubiquitously found enzyme is involved in gaseous CO₂ sequestration and is being looked as a promising candidate for combating global warming. Efforts are also being made to mimic the reaction for fixation of anthropogenic CO₂ into bi-carbonate using carbonic anhydrase (CA) as a biocatalyst. CA is being employed to accelerate the rate of hydration of CO₂ to form carbonate ions and proton. Presently, carbonate is being precipitated from aqueous solution as calcium carbonate given a suitable saturation of calcium and carbonate ions by addition of appropriate buffer. A unique protocol for the synthesis of stabilized enzyme nanoparticles (SENs) has been developed for CA to stabilize the enzyme activity by encapsulating each enzyme molecule with a hybrid organic/inorganic polymer network using chitosan and silane.  Since, SENs are still in nanometer scale and soluble in aqueous buffer, they can be further immobilized into nanoporous materials. As such, this hierarchical approach allows separate control over stabilization and immobilization in a nanoporous host.  Also new molecule and functionalized bio-materials are being developed for capture of carbon dioxide with sorption capacity in the range of 100-200mgof CO₂/g of material or molecule. The regeneration of these new molecules are being attempted by using carbonic anhydrase with very encouraging results by exploiting the reversible reaction of CA with bicarbonate to release CO₂.

ii) CO₂ capture and valorization: New hybrid process has been developed for generation of chemical and fuels including syngas, formic acid , methane and hythane  by coupling enzyme driven biomimetic carbonation with photocatalysis based chemical looping reaction (CLR).  Carbonic anhydrase is being tested for its catalytic  interaction with carbon dioxide in presence of  suitable catalysts including Titania and appropriate co-catalysts. An innovative approach to generate syngas and other chemicals has been identified by photo catalytically reducing the bicarbonate/carbonate rich stream to carbon monoxide and formaldehyde . The process developed is clean and green by virtue of the fact that it ensures i) Pt and organic donor free system ii) sustained generation of CO, hydrogen and formic acid  iii) ensures stability of carbonic anhydrase by flux engineering iv) concomitant avoidance of buffering of the system and v) usage of  carbonates  as sacrificial donor . The rate   of hydrogen and CO evolution in syngas is 124.16µmols/4h and 1.949µmols/4h, respectively .The utilization of CO₂ as a building block in a Pt and donor free system using this new approach of PC-CLR may represent an interesting approach to synthetic methodologies less intensive in carbon and energy. Also, the production of chemicals and fuels instead of concentrated CO₂stream /carbonates as end products during biomimetic carbonation may make the process commercially viable to be adopted by industries emitting carbon dioxide. The engineered methanation process is being developed for generation of methane from calcite as well as bicarbonate with methane evolution rate of 4.3µmol/h .

Engineered materials and processes ensures cleaner and greener and sustainable environment. 

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