Rational Design of Highly Active and Sensitive Graphene Oxide-based Catalyst and Sensor Materials

Abstract

Graphene oxide with its unique structure and properties have attracted a huge attention of the researchers in world wide. It is a 2D material containing carbon network of sp2 and sp3 hybridization with numerous polar oxygen functional groups such as carboxyl, hydroxyl and carbonyl groups. The unique properties like high surface area, thermal stability, tunable electrical properties and mechanical properties make GO a suitable support material to design a wide range of active and efficient hybrid materials for various potential applications.
Keeping this in mind, the overall objectives of my PhD research work is broadly classified in to two parts; (1) synthesis of acid functionalised GO-based hybrid materials such as phosphate functionalised GO (PGO), PGO/CuO and silicomolybdic acid modified GO (GO-SMA) and their catalytic applications for the synthesis of biologically active nitrogen-based heterocycles and (2) Synthesis of spinel ferrite decorated rGO-based nanocomposites such as rGO-CuFe2O4 and rGO-ZnFe2O4-Pd towards gas sensing applications for the detection of toxic and flammable gases. At the beginning of my PhD work, a very less number of literature(s) were available demonstrating the use of acid functionalized GO-based catalyst for the synthesis of biologically active nitrogen-based heterocycles. In the first major project, phosphate functionalized GO (PGO) nanocomposite was synthesized and utilized as potential catalyst for the synthesis of Pyrimidones (Chem. Eng. J., 2018, 331, 300). The high catalytic activity of PGO nanocatalyst can be attributed to the synergistic effect present between GO and phosphate groups. Highlighting the effect of nanoparticle decoration on the catalytic activity of acid functionalized GO, in our next project metal oxide nanoparticles were decorated on PGO surface to design a novel highly active and recyclable heterogeneous catalyst for the synthesis of β-amino carbonyl compounds. Here, PGO surface was decorated by CuO nanoparticles uniformly and the resulting hybrids showed enhanced catalytic activity towards the desired product (Catal. Today, 2020, 348, 137). This approach offers several advantages such as short reaction times, high yields, easy purification, a cleaner reaction , ease of recovery and reusability of the catalyst. Highlighting the synergistic effect present between the acidic groups and GO surface, our next objective emphasized the DFT analysis of acid functionalized GO (GO with silicomolybdic acid) in the synthesis of Isoxazoles, another biologically active nitrogen-based heterocyclic molecule (Manuscript Submitted).
The next major part of my PhD research includes spinel ferrites decorated rGO nanocomposites for the detection of toxic and flammable gases. In this regard, the fourth objective explains about the synthesis of rGO-CuFe2O4 nanocomposite for the detection of low level NH3 gas (Sens. and Actuators B: Chem., 2018, 272, 100). The designed nanocomposite was able to sense a very low concentration of NH3 gas with high sensitivity. Additionally, the fast response and recovery of the sensor makes it a suitable candidate for practical application. The last objective emphasizes the effect of nanoparticle decoration on the sensing parameters of the spinel ferrite rGO-based gas sensor. In this objective we have designed Pd nanoparticles decorated rGO-ZnFe2O4 nanocomposite for the detection of highly flammable H2 gas at room temperature (Int. J. Hydrog. Energy, 2020, 45, 5073). In this work, a rapid and efficient microwave synthetic method has been adopted for the sythesis of ZnFe2O4-Pd nanocomposite followed by decoration on thermally reduced rGO surface. It can be ascribed that due to the superior charge transfer process, synergistic effect, high surface area, as well as superior durability of the composite rGO-based spinel ferrite systems can be regarded as suitable candidate for gas sensing applications.