Utilization of 2D MXene nano particles in vanadium redox flow batteries

Vanadium redox flow batteries (VRFBs) have emerged as a well-established, inherently safe, highly modular, and flexible energy storage technology with the unique capability of decoupling power and energy thanks to their architectural advantages. They have high round trip efficiencies and do not decay because of the high depth of discharges. Their responsiveness is quite fast and the aqueous vanadium electrolytes are environmentally friendly. The scalability of flow batteries, which is more cost-effective compared to other solid-state electrochemical systems, overcomes their low power and energy density limitations. Therefore, VRFBs can offer a practical solution to bridge the gap between the adaptation of renewable resources and the recent, increasing demands of the energy market. In VRFBs, redox reactions take place at active sites across the electrode surface without causing any morphological change and/or phase transformations to the electrodes. Carbon felt, graphite felt, and carbon paper are the most used electrode materials to date in VRFBs. However, these carbonaceous materials intrinsically suffer from low electrochemically active surface area, insufficient wetting, and poor kinetic reversibility issues. To overcome these problems and improve carbonaceous electrode performance, electrode surface modification via nanoparticles is an effective way. The research started with precious metals, and metal oxides eventually dwelled on carbon-based electrocatalysts. Although nano particles have already proven their efficacy as catalyst materials in VRFBs, a unique 2-dimensional (2D) nano material, referred to as MXenes, has not received attention despite having been first reported a decade ago in Drexel University. Motivated by this, the primary objective of this Ph.D. thesis is to investigate Ti3C2Tx MXene as a novel anode nano catalyst material in VRFBs. Therefore, one of the most substantial focal points of this work is to understand the effects of physicochemical material properties of 2D MXene sheets on the critical aspects of the performance of VRFBs. Novel methods of Ti3C2Tx MXene utilization in VRFBs were proposed and extensively tested. Electrochemical methods were broadly utilized to analyze battery performance of MXene nanoflakes in various applications such as electrode coating, nanofluidic anolyte, and slurry electrode applications. Lastly, the hydrodynamic behavior of Ti3C2Tx nanoflakes and its effect on battery performance were studied as an essential part of this Ph.D. thesis.