Graphene based materials : Mechanistic insights into corrosion inhibition and supercapacitance

Abstract

In the contemporary scenario, protecting metals and alloys from deterioration through the coating is the main concern that extracts worldwide attention. Although existing coating processes and methods such as epoxy coatings and polymer composite coating are already considerably invented and improved, further progress is still essential in terms of economical, nature-friendly, and long-term protection. So to overcome these issues, organic-based coatings have been drawn escalating consideration and became the most efficient ways to shield a metal substrate. Among them, Graphene Oxide (GO)-based functionalized hydrophobic coating materials have been extensively investigated in the last decades. This thesis demonstrates that a very thin sub-nanometric layer of GO on a metal surface has excellent long-term anti-corrosive properties against a very harsh saline environment. Furthermore, we have shown a direction to choose an organic grafting agent among para-aminobenzoic acid (PABA), alanine, and glycine in a very economical way to enhance the anti-corrosion behavior of GO. In addition, recently, the derivatives of graphene have become the center of attraction among the materials used for supercapacitors. Graphene as electrode material in supercapacitors does not exhibit the required energy and power output when used in its ideal form. Earlier reports have shown that graphene necessitates the doping of heteroatoms such as N, S, B, P etc., to alter and amend its Physico-chemical and electrochemical behaviors. In most of those reports, merely a few milligrams of GO precursor were taken to get rid of the agglomeration problem in the dispersion medium. This is due to the fact that a greater amount of graphene oxide often leads to the poor reduction and exfoliation of GO. Thus, the up-scaling in the productivity of N-doped rGO (N-rGO) using such reported synthesis methods is quite challenging. Hence, efficient, straightforward, and inexpensive synthesis techniques for the synthesis of N-rGO are still not fully explored. Considering all the above drawbacks in mind, we have attempted a synthesis by ta= king GO, a comparatively large amount of precursor, to provide the roadmap for the up-scaled synthesis of N-rGO by solvothermal synthesis method, which is simple and more accessible. In this thesis, we have demonstrated the synthesis, characterization, and anti-corrosive properties of GO/PABA thin coating on iron metal in 1 M KCl (aq. solution) saline medium. Furthermore, we investigated the non-expensive amino acids (Alanine and Glycine) as grafting agents to protect the iron metal by a thin layer of GO coating in a highly saline (3 M KCl aq. solution) medium. Furthermore, experimentally and theoretically, we illustrated the investigation of the role of oxygen functionality through GO/rGO/N-rGO coating to protect the iron metal from corrosion. For exploring the supercapacitors, we examined the role of N-doping in reduced graphene oxide to enhance the supercapacitance at different precursor ratios. Later on, we explored the role of precursor content, synthesis time, and dispersive solvent for maximizing the supercapacitance of N-rGO sheet.