Optimization of Chemical Synthesis and Characterization of Supported Metal Alloy Nanoparticles for Oxygen Evolution Reaction

Abstract

The search for green and reliable energy alternatives to fossil fuels has been the mainstream topic of concern to the global community. This is due to the diminishing natural fossil fuels and the release of greenhouse gases which badly impact the environment. In this regard, researchers perceive a great scope in water splitting which can use the vast and renewable water resources for the generation of hydrogen (H2) and oxygen (O2) gases. Electrochemical water splitting shows an excellent potential for producing H2 fuel through hydrogen evolution reaction (HER) at the cathode using highly efficient electrocatalysts. Simultaneously, the oxygen evolution reaction (OER) at the anode is very typical in overall water splitting, being the limiting reaction in the whole process. Hence, the synthesis of electrocatalysts favouring OER is the main focus of our work in this thesis.

In this work, CuNi supported on graphene variant (graphene oxides (GO) and reduced graphene oxides(rGO)) has been studied and used as an OER electrocatalyst. From the literature, Cu-based and nickel-based materials have shown high OER electrocatalytic activity. The supported CuNi alloy has demonstrated high activity due to the synergistic properties of the combined species. The graphene variants were synthesized using the modified Hummer’s process, while the CuNi alloy was developed over the graphene surface using a typical solvothermal method. All materials were characterized using numerous characterization techniques, which were X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform Infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission electron Microscopy (TEM) and Energy Dispersive spectroscopy (EDX) to confirm the structure, properties, and composition of the as-synthesized materials. The FT-IR and Raman spectra results confirmed the presence of -COOH and OH functional groups on the surface of the graphene oxide. While the XPS confirmed the formation of the supported alloy with the expected compositions based on the shift of the Cu and Ni binding energy, indicating the interaction between the two metals. The as prepared materials were proficient and effective for oxygen evolution reaction (OER) in 1M KOH. The copper nickel alloy with reduced graphene oxide (CuNi/rGO) catalyst outperformed the other three Cu-based electrocatalysts in 1.0 M KOH solution, with a low onset potential (1.56 vs. RHE), large electrochemical surface area (8.2 x 10-5 cm-2), and low charge transfer resistance (5 ohms). From the results of the studies, this research could provide insights into low-cost electrocatalysts for OER.

Date of Award	Apr 2023
Original language	American English
Supervisor	AHSAN Qurashi (Supervisor)