http://theses.ncl.ac.uk/jspui/handle/10443/4094 2026-04-26T23:19:43Z 2026-04-26T23:19:43Z Jiang, Jianan http://theses.ncl.ac.uk/jspui/handle/10443/6746 2026-04-24T11:19:43Z 2025-01-01T00:00:00Z

Title: A novel transition metal dichalcogenide – reduced graphene oxide electrocatalyst family for hydrogen evolution reaction Authors: Jiang, Jianan Abstract: The global energy crisis underscores the critical need for sustainable hydrogen production via efficient electrocatalysts. This study presents a novel family of transition metal dichalcogenide-reduced graphene oxide (MoS2-rGO) hybrids and doped variants (V, W, Co) for the hydrogen evolution reaction (HER). Using orthogonal experimental design (L9(33)), we optimized synthesis parameters (rGO content, heating temperature, duration) to develop a MoS2-rGO composite with 0.8 wt% rGO, synthesized at 200°C for 24 h. This optimized catalyst achieved superior HER performance in acidic media (0.5 M H2SO4), exhibiting a low overpotential (η10 = -0.34 Vs RHE) and Tafel slope (98.2 mV/dec), significantly outperforming undoped MoS2 (η10 > 0.40 Vs RHE, Tafel slope 113.0 mV/dec). While Pt/C remains the benchmark catalyst with ultra-low overpotential (~0.05 V vs. RHE) and a Tafel slope of ~30 mV/dec, its high cost and scarcity hinder widespread application. In contrast, our MoS2-rGO catalysts offer a noble-metal-free alternative with enhanced conductivity and stability, facilitated by rGO integration. XRD and Raman spectroscopy confirmed structural improvements, while vanadium doping increased active site exposure, tungsten doping introduced sulfur vacancies to optimize hydrogen adsorption energy, and cobalt doping altered electronic structures. Systematic characterization via XRD, XPS, BET, UV-vis, Raman spectroscopy, SEM and electrochemical techniques elucidated the structural and electronic contributions of each component. The synergistic effects of rGO and dopants were highlighted, with the Co0.05W0.05S2/rGO heterostructure showing promising HER activity. This work establishes a rational framework for designing noble-metal-free HER catalysts, emphasizing the interplay between defect engineering, interfacial interactions, and scalable synthesis strategies. The integration of orthogonal optimization with multi-technique characterization provides a robust pathway for advancing green hydrogen technologies. Description: Ph. D. Thesis.

2025-01-01T00:00:00Z Thaman, Narryn I J http://theses.ncl.ac.uk/jspui/handle/10443/6742 2026-04-17T14:03:50Z 2025-01-01T00:00:00Z

Title: The development of four dimensional electrical resistivity tomography for laboratory-scale imaging of soil moisture dynamics Authors: Thaman, Narryn I J Abstract: This study considers the combination of a novel geophysical monitoring system and geotechnical point sensors for use in controlled laboratory conditions to visualise soil moisture dynamics in different engineered soils. The geophysical monitoring system, referred to here as PRIME (Proactive Infrastructure Monitoring and Evaluation system), uses electrical resistivity tomography (ERT) technology to non-invasively image subsurface moisture-driven processes. The PRIME system and point sensor arrays have been developed for near real-time data acquisition of transient soil moisture conditions in a suite of soil column experiments. This research aims to provide new tools and approaches to further our understanding of soil moisture movement to better assess shallow geotechnical assets by addressing the challenges associated with designing integrated geophysical-geotechnical laboratory-scale monitoring experiments. A total of nine soil column experiments were carried out in this research. Soil moisture content, grain size and density were changed throughout the study to gauge the proficiency of time-lapse ERT for various soils. Nine soil column experiments were conducted to evaluate the effectiveness of time-lapse ERT in various soil compositions, assessing changes in moisture content, grain size, and density. One of the main challenges associated with integrating ERT in a soil column setup is the prevalence of artefacts in the time-lapse imaging. These artefacts, presenting as high or low electrical resistivity contrasts, can be a common feature in ERT surveys and are known to reduce the accuracy of the inversion. This study takes steps to reduce the tendency of artefacts in the results by systematically identifying the source of such modelling errors and adapting the 4D ERT integrated soil column design accordingly. Alongside plotting the electrical resistivity of transient soil moisture conditions in the column experiments, petrophysical relationships derived from the ERT soil columns focus on understanding the link between soil moisture content, electrical resistivity, and suction. These relationships are crucial for improving the interpretation of time-lapse ERT data and enhancing the accuracy of soil moisture monitoring in laboratory and field applications. Findings demonstrate the potential of integrating ERT with geotechnical monitoring systems to advance understanding of soil moisture movement, with applications in geotechnical asset management and environmental engineering. Description: PhD Thesis

2025-01-01T00:00:00Z Asiedu-Asante, Ama Baduba http://theses.ncl.ac.uk/jspui/handle/10443/6738 2026-04-17T08:32:49Z 2025-01-01T00:00:00Z

Title: Investigation of Frequency Domain Reflectometry as a Degradation Monitoring Technique for Lithium-Ion Batteries Authors: Asiedu-Asante, Ama Baduba Abstract: Frequency Domain Reflectometry (FDR) is an impedance-based diagnostic technique traditionally used in power systems to assess impedance changes in power cables. Recently, FDR has been applied to battery systems to measure high-frequency impedance, which is valuable for understanding battery performance in power line communication networks and assessing electromagnetic compatibility (EMC). Previous studies have highlighted FDR's ability to detect high-frequency processes like skin effect and ionic shunt effect, and its sensitivity to factors such as charging current, state of charge (SoC), and temperature. However, its potential for monitoring battery State of Health (SoH) has not been thoroughly explored. This thesis investigates the use of FDR as a non-invasive, tool for monitoring SoH of lithium ion batteries. The study involved two main stages of analysis. First, FDR was used to measure the impedance of 19 commercial coin cells (LIR 2032) across a frequency range of 300 kHz to 1 GHz. These cells were aged to varying SoH levels through controlled cyclic aging, and their SoH was benchmarked using Electrochemical Impedance Spectroscopy (EIS). The FDR impedance measurements were then compared to health indicators like battery capacity and internal resistance to evaluate FDR's sensitivity and accuracy in detecting aging-induced changes. The second stage involved a statistical evaluation of FDR's effectiveness in data driven detection and prediction models, using techniques such as principal component analysis, multivariate statistical process control, and partial least squares regression. The findings show that while FDR can detect changes in battery impedance related to aging, it has limitations in sensitivity to slower degradation processes and accuracy at lower impedance values. FDR demonstrated potential for single-cell SoH tracking but was less effective for multi-cell detection and capacity prediction compared to EIS. Despite these limitations, FDR could complement other health indicators in a multi-metric battery monitoring system, provided that careful setup design and calibration are employed. Description: PhD Thesis

2025-01-01T00:00:00Z Amicarelli, Gianluca http://theses.ncl.ac.uk/jspui/handle/10443/6737 2026-04-17T08:24:20Z 2025-01-01T00:00:00Z

Title: A Multiscale Investigation of Fracture Networks Interpreted from Aerial and Drone Imagery Authors: Amicarelli, Gianluca Abstract: This PhD thesis focuses on advancing the understanding and characterization of geological fracture networks using aerial and drone imagery, and automated fracture extraction methods. The research addresses three primary questions: the reliability and robustness of automated fracture extraction methods when applied to decimeter resolution aerial imagery, the effects of varying imaging resolutions on the interpretation of fault and fracture networks, and how spatial and resolution dependent variability in fracture networks impacts geological interpretations. The studies carried out throughout this research employ a multiscale approach, using datasets of varying resolutions, from aerial imagery at 0.2 m/px to field imagery at 0.002 m/px, to quantify the information loss across different resolutions. Automated extraction methods, specifically the Complex Shearlet Transform and Binary Thresholding Method, were tested for their reliability and reproducibility. Results reveal that currently, automated fracture extraction methods face challenges, specifically with the reliable extraction of fractures from low-resolution datasets. It was found that the accuracy and reliability of these methods are significantly impacted by the resolution of the input data and by exposure continuity. Reliability was quantified by measuring the Root Mean Square Error (RMSE) of fracture lengths between different automated approaches, which revealed significant discrepancies, indicating that these methods often produce inconsistent results when applied to the same datasets. The impact of image resolution on fracture network properties was investigated and quantified using manual approaches. High-resolution imagery (0.02 cm) captures fine-scale features but is limited by area-bound censoring. Medium resolution (2 cm) imagery offers a balanced view, identifying a broad range of fracture lengths and characteristics. Low-resolution imagery (20 cm) covers extensive areas ii but often misses finer fractures, leading to severe fine-scale fracture censoring. A multiscale approach and rigorous tracing methodology are essential for accurate geological analysis. Finally, a case study on the granitic rocks of west Hitra Island, Norway, using imagery at three different scales (regional, local, and outcrop scales) demonstrates that accurate geological interpretations are possible using imagery alone. This study also stresses the importance of applying clearly defined criteria when using manual methods with decimeter-resolution imagery to ensure reliable results. Description: PhD Thesis

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