Modified Reduced Graphene Oxide-based Nanocomposites With Non-precious Metals:Synthesis,Characterization And Applications

Since the first appearance in 2004,graphene and its derivatives have gained vast attention in different fields and created a revolution in many different branches of science and especially in materials science,owing to their astonishing,unique and novel physical and chemical properties.These desirable properties have inspired the development of low-cost and high-yield preparation methods of chemically-derived graphene(reduced graphene oxide).The initial popularity of GO was due to a synthetic means towards obtaining graphene.The fundamental principle behind this approach was to obtain high-quality graphene(i.e.with a defined sp2 domain)with extraordinary electronic,optical and mechanical properties.But its yield was significantly restrained by CVD growth method.Realizing a chemical means towards the achievement of large-scale sheets of graphene would afford an incredible boost towards making graphene more accessible to be realized in the applications.The chemical reduction of graphene oxide(GO)is the most promising and effective method for the synthesis of reduced graphene oxide(rGO)because of its relatively large scale and low cost.Additionally,many investigations focused on the applications of graphene-based composites as catalysts for pollutants removal.Also,modified graphene can adsorb heavy metal ions with high efficiency and selectivity,and thus reduces them to metals for recycling.The objective of my thesis is to develop facile,environmentally friendly,low cost,and controllable approaches for modification of GO and its decoration with metal and metal oxide nanoparticles.These techniques use simple thermal treatment,doping with heteroatoms,and then the synthesis of composites with the special focus on greener synthesis,avoiding toxic/explosive reducing agents and achieving porosity and composite formation without addition of any capping agent,organic linkers or template agents.This research work is essentially comprised of three major projects that are briefly introduced hereIn the first project,A simple strategy was successfully adopted to synthesize TErGO/Ni3C-Ni.The fast reaction kinetics and excellent stability of the TErGO/Ni3C-Ni can be attributed to the large surface area,better conductivity,high adsorption ability,and chemical stability of TErGO combing with the crystalline Ni3C-Ni nanoparticles.No toxic,explosive nature reducing agent such as N2H4 utilized during synthesis nor organic linker,capping and templating agent required for uniform dispersion of nanoparticles and to obtain porous architecture with large pore volume and narrow pore diameter.The effect of thermal treatment of GO was comprehensively investigated and possible factors for high performance of the nanocomposite were discussed in details.The better reduction of TErGO provides a medium for easy and fast transfer of electrons during reduction process.Furthermore,TErGO/Ni3C-Ni displayed HCOOH induced reduction of Cr(VI)to Cr(?)with 100%reduction achieved within 1 minute with an extraordinary rate constant value of 2.74 min-1.TErGO/Ni3C-Ni exhibited a phenomenally high Specific Removal Rate(SRR)value of 0.29 mg of Cr(VI)min-1 mg-1 of TErGO/Ni3C-Ni.The TErGO/Ni3C-Ni also degraded organic dyes with an excellent rate and also proved a fast-reducing catalyst for reduction of 4-nitrophenol to 4-aminophenol.The strategy provides an easy way to prepare high performance nanohybrids of non-noble metals which can be applied in the fields of energy storage and production,environmental and electrochemical catalysis.This also opens new opportunities for further enhancement in performance of noble metal nanohybrids using similar strategy under mild reaction conditions.The second project discuss the synthesis N-doped reduced graphene oxide(NrGO)and NrGO/Fe3O4 nanocomposite adsorbents for phosphate removal from wastewater,Phosphate deduction is an essential measure compulsory to control eutrophication of water bodies as it hinders disproportionate algae development.Presently existing phosphate removal approaches have several limitations.This study successfully prepared and characterized a nitrogen doped reduced graphene oxide(NrGO)and nitrogen doped reduced graphene oxide decorated with Fe3O4 nanoparticles as nanocomposite adsorbent which has high capacity and specific affinity towards phosphate.The kinetic study suggests the pseudo second order better fitted the phosphate adsorption with physisorption and chemisorption.The Freundlich isotherm model better fitted the phosphate adsorption with removal capacity of 169.7 mg g-1 while reaction mechanism confirms the successful phosphate adsorption by composite material.This study provides an easy synthesis of graphene oxide magnetic composite materials with potential application on a large scale.In the third project,we introduce an inexpensive,highly effective,and facile approach to the synthesis of rGO/Fe3O4 composite which is then employed as anode material for lithium ion batteries(LIBs).The Fe3O4 nanoparticles(NPs)homogenously covered the surface of reduced graphene oxide without seen any aggregation forming the layered composite structure.The as prepared RGO/Fe3O4 composite exhibited high specific capacity along with stable reversible capacity(701.8 mAh/g at 200 mAg'1 up to 50 cycles),improvement in rate capability,as well as reduced voltage hysteresis.The porous nature of rGO/Fe3O4 composite in layered form,conductivity and the vital role of confinement and dispersion of Fe3O4 NPs by monolayers of reduced graphene can be attributed for better electrochemical properties of the synthesized composite material.