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The ever-increasing demand for renewable energy resources has encouraged the development of electrochemical energy storage technologies that are able to store and deliver electrical energy when and where it is required. Redox flow batteries (RFBs) are a promising response to this demand, as they can help to not only reduce the unpredictability of the sources such as solar and wind energy, but also provide backup power and reduce the reliance on fossil fuels towards 2050 net zero emission targets. The Vanadium Redox Flow Battery (VFRB) as a well-stablished flow battery is one of the main potential candidates for large-scale energy storage systems due to its advantages of higher round-trip efficiency of typically between 75%-85%, long cycle life - suggested to be over 20 years with appropriate maintenance, lower maintenance due to the stability of the all-vanadium electrolyte and not having much crossover contamination. These pros make the VRFB competitive in flow battery technologies. However, the world-wide implementation of VRFBs is restricted due to the problems of low energy and power density which are mainly associated with the electrolyte and electrode. Although researchers have been focusing on improving the electrochemical properties and the battery’s performance using different modifications to the electrolyte and electrode, one of the issues that still exists in some of the research-scale VRFBs is the detachment of the catalysts and precipitation which causes capacity decay over cycling. In this thesis, a rarely studied approach of utilizing nanofluidic electrolyte was extensively investigated and applied into the VRFB to analyse the effectiveness of the concept with novel 2D materials. [...], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, Full Text

The incorporation of multiphysics stimuli with traditional sensing effects results in an approach for increasing the sensitivity of mechanical sensors, in particular strain sensing. This paper reports on the giant piezotronic effect in a p-GaN/AlGaN/GaN heterojunction coupled with UV illumination and tuning current that can reach a strain sensitivity of as high as 70680. In comparison to an identical configuration without coupling, this value represents a 100-fold improvement. This sensitivity is one of the greatest for the piezotronic effect in semiconductors that have been documented to date. The intensification of the piezotronic effect in the p-GaN/AlGaN/GaN heterojunctions was ascribed to the formation of a carrier concentration gradient in the AlGaN and GaN layers under UV illumination coupled with the potential-balancing effect by a tuning current. In addition, the result showed a significant improvement in repeatability, stability, and detectable range of the strain sensor utilizing this phenomenon. The ultrahigh sensitivity strain sensing technique will open the way for the establishment of mechanical sensors that are tremendously sensitive, trustworthy, and efficient.

Development of the Vanadium Redox Flow Battery (VRFB) has been widely reported but typically only focuses on one part of the cell (e.g. electrode, electrolyte, or membrane). Improvement to a single part of the cell may cause side effects on other parts during long-term cycling leading to an overall drop in the performance of the battery. To avoid this, the use of nanofluidic electrolyte seems to be a promising approach to enhance the performance of both electrode and electrolyte simultaneously. This paper aims to investigate the electrochemical performance of a newly prepared reduced graphene oxide (rGO) nanofluidic vanadium electrolyte, applicable for Vanadium Redox Flow Batteries (VRFB). Herein, we report for the first time a stable rGO/vanadium nanofluidic electrolyte with improved electrochemical performance. Benefiting from the low degree of oxidation as compared to GO, the rGO can provide high electrical conduction due to the presence of sufficient functional groups, which can facilitate the redox reactions. The effect of various concentrations of rGO on the electrochemical performance is investigated. The current collector (carbon cloth (CC) electrode) was further characterized using different physico-chemical techniques to underpin the stability of rGO nanofluids. The results suggested that the electrochemical performance of vanadium electrolyte increases with the concentration of rGO. Improvements of approx. 15% to 20% were achieved in peak potential separation and current density rates, respectively. In addition, the incorporation of rGO in nanofluidic electrolyte significantly decreases the electrolyte and charge transfer resistance by ∼10% and ∼99%, respectively, and improves the vanadium ion diffusion process by ∼50%.