The depletion of traditional fossil fuels on such a comprehensive scale has led to calamitous global climate change and severe environmental concerns [1-3]. Hydrogen is a promising candidate to replace existing finite petroleum-based energy sources because of its remarkable gravimetric energy density, clean combustion and abundance [4]. However, the storing of hydrogen presents significant challenges because of its low volumetric density at ambient temperatures [5]. Currently, the industry standard for storage is to highly compress hydrogen at ambient temperatures. This strategy suffers from eventual compression losses and demands lightweight, mechanically high performing and costly containment structures.
Nanoporous materials have demonstrated the ability to adsorb hydrogen allowing for it to be stored at high densities under specific conditions; often extremely low temperatures, high pressures, or both [6]. As a result, their application to systems that require more modest working conditions (such as transportation applications) has been restricted. Designing and conceiving materials for adsorption that can successfully store and relinquish hydrogen at ambient conditions continues to be an important challenge.
A specific class of nanoporous polymer known as conjugated microporous polymers (CMPs) exhibit highly cross-linked three-dimensional porous networks in an amorphous fashion that results in both high thermal and chemical stability [7]. CMPs have been used in a range of applications, including the adsorption and capture of gases such as carbon dioxide [8], but their hydrogen storage capabilities have received considerably less attention. This project aims to investigate the potential of CMPs and composites formed from these materials for safe and efficient hydrogen storage.
Design and synthesis of a range of CMPs using an established metal catalysed cross-coupling reaction (Buchwald-Hartwig coupling) will be conducted before characterisation of the physical properties of the resulting material using standardised techniques including gas sorption analysis (to determine specific surface area, pore volume and pore size), thermogravimetric analysis, X-ray diffraction, ultraviolet-visible spectroscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy and transmission electron microscopy.
Selected high performing CMPs may be blended with various matrices to form a composite that offers numerous advantages over the raw powdered counterpart in terms of safety, handling and practical manufacturing. An evaluation of the performance of these materials in the composite form will be conducted, including an assessment of their stability and mechanical properties, in order to conclude if these materials could contribute to the hydrogen storage field by either increasing hydrogen storage capabilities or decreasing the required operating pressure in hydrogen storage vessels and ultimately contribute towards carbon neutrality/net zero.