Author

Wen Sun

Date of Award

December 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Julia J. Zhao

Abstract

The work described in this dissertation will have three primary goals that are all essential for improving the energy demand using nanotechnology. The first goal is to comprehensively understand the application of SiO2-based nanoparticles (SiO2-based-NPs) in enhanced oil recovery (EOR) and the challenges associated with their use. The second goal is to investigate the application of ruthenium-based nanoparticles using reduced graphene oxide as the matrix (Runano-based/rGO) for the electrochemical synthesis of ammonia under ambient conditions. The third goal is to develop binder-free 3D nanomaterials and assess their electrochemical properties for supercapacitor applications. To fulfill this goal, two different nanomaterials have been synthesized, one is nickel cobalt with reduced graphene oxide nanonetwork on nickel foam (NC-rGO@Ni-foam). The NC-rGO@Ni-foam can be used at relatively positive potential and exhibit pseudocapacitor behavior. The other material is carbonized humic acid on nickel foam (CHA@Ni-foam) used at relatively negative potential and exhibits electrical double-layer capacitor (EDLC) behavior.The first project provides a comprehensive understanding of the applications of SiO2-based-NPs in EOR and the challenges associated with their use. It covers four methods of making nanoparticles, explores how SiO2-based-NPs involved nanofluids affect the EOR process, discusses the underlying mechanisms of nanoparticles-based EOR, briefly mentions how instrumentation is used in the oil and gas industry, and addresses the challenges of using SiO2-based nanoparticles in EOR, while also suggesting areas for future research. In the second project, a ruthenium-based nitrogen reduction nanocatalyst has been developed using rGO as a matrix. The nanocatalyst synthesis was based on a single-step simultaneous reduction of RuCl3 into ruthenium-based nanoparticles (Ru-based-NPs) and graphene oxide (GO) into rGO using glucose as the reducing agent and stabilizer. The obtained ruthenium-based nanocatalyst with rGO as a matrix (Runano-based/rGO) has shown much higher catalytic activity at lower temperatures and pressures for ammonia synthesis than conventional iron catalysts. The rGO worked as a promising promoter for the electrochemical synthesis of ammonia due to its excellent electrical and thermal conductivity. The results demonstrated that the size of the Ru-based NPs on the surface of rGO was 1.9 ± 0.2nm and the ruthenium content was 25.03 wt %. Bulk electrolysis measurements were conducted on thin-layer electrodes at various cathodic potentials in an N2-saturated 0.1 M H2SO4 electrolyte at room temperature. From the chronoamperometric measurements, the maximum faradic efficiency (F.E.) of 2.1% for ammonia production on the nanostructured Runano-based/rGO electrocatalyst was achieved at a potential of -0.20 V vs reversible hydrogen electrode (RHE). This electrocatalyst has attained a superior ammonia production rate of 9.14 μg·h−1·mgcat.−1. The results demonstrate the feasibility of reducing N2 into ammonia under ambient conditions and warrant further exploration of the nanostructured Runano-based/rGO for electrochemical ammonia synthesis. The third and fourth projects focus on the synthesis of binder-free nanomaterials and their applications in supercapacitors. In the third project, to enhance the electrochemical properties for supercapacitor applications, a 3D structured nanoflower was developed using an in situ wet-chemical method, and hydrothermal method to get the architecture of inserting divalent metal ions (Ni2+ and Co2+) into rGO layers on Ni-foam (3D NC-rGO@Ni-foam). The resulting NC-rGO nanostructures on the nickel skeleton exhibit strong adhesion, facilitating fast redox reactions and efficient electrochemical energy storage. The microstructure, composition, and electrochemical properties of this 3D NC-rGO@Ni-foam electrode material were systematically characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and other techniques. Notably, this material exhibited a good specific capacitance (Cs) of 2612 F/g at 1A/g. Furthermore, the symmetric supercapacitor device constructed from this material exhibited a high energy density of 37.1 W·h/kg and a power density of 430 W/kg within a potential range of 2.4 V. The electrochemical properties and mechanical integrity of 3D NC-rGO@Ni-foam suggest its potential as an advanced electrode material for scalable energy storage devices. The fourth project is the first time a binder-free nanonetwork was synthesized using humic acid from coal as the precursor. The hydrothermal method and calcination process have been used to prepare CHA@Ni-foam and this material has been used as electrode material for EDLC applications. This binder-free CHA@Ni-foam exhibited an excellent Cs of 905.3 F/g (at 1.15 A/g) which is 3 times higher than that of ever reported. Furthermore, the symmetric supercapacitor device constructed from this material exhibited a high energy density of 75.0 W·h/kg and a power density of 150.2 W/kg within a potential range of 1.6 V. This first-time synthesized binder-free NC-rGO@Ni-foam from coal-based humic acid has potential as an advanced EDLC electrode material for scalable energy storage devices.

Available for download on Saturday, January 17, 2026

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