Advanced Hydrogen Storage and Delivery Materials, Chemical Production of Metal Nanowires and Nanoparticles, Inorganic Electrides and Alkalide Anions in Zeolites, Host–Guest Chemistry of Framework Materials, Nanostructured Materials
Hydrogen Storage Chemistry Group (HSCG)
The HSCG has an extensive ongoing programme, dedicated to the discovery, synthesis and primary characterization of new potential hydrogen storage materials, for use either in safe hydrogen delivery systems or reversible hydrogen stores. In the last six years, the group has synthesized over two dozen new complex hydrides, contributing substantially to a rapid growth in the number of such compounds considered as candidate hydrogen storage materials.
The group maintains a strong focus on achieving a better understanding of fundamental aspects of the interaction of hydrogen with solids, and of the chemistry of hydrogen desorption and reabsorption. Examples of approaches employed include: the modification of the decomposition pathway of lithium amide in favour of hydrogen rather than ammonia, through the substitution of borohydride anions for one quarter of the amide anions to produce the first example of a new class of amide–borohydride compounds; and.the chemical activation of magnesium hydride to achieve fast absorption–desorption kinetics, without recourse either to mechanical milling or the addition of a precious metal catalyst.
Current work is focused on enhancing the ionic conductivity of lithium containing complex hydrides as an alternative or complementary approach to precious metal catalysis in improving absorption–desorption kinetics, on new ultra-high hydrogen capacity complex hydrides, and also on attempts to improve the binding strength of molecular hydrogen in porous framework materials to achieve usable hydrogen storage capacities at or near room temperature. The group is an active partner in the AWM Science City Hydrogen Energy Project and the EPSRC-funded UK Sustainable Hydrogen Energy Consortium (UKSHEC 2).
Host–Guest Chemistry in Framework Materials
The second major strand in Paul’s research for many years has been the chemical manipulation of the nanoscale pore space of porous crystalline materials. Zeolites and related framework structures may be used as both precursors and templates in the synthesis of materials with controlled morphologies at the nanoscale and sub-nanoscale level.
Performing a 'molecular scaffolding' function, they facilitate the assembly of advanced materials with finely tuned electronic, magnetic and optical properties. Examples include atomically fine chains of metal atoms (atomic wires), ordered arrays of interacting metal or semiconductor clusters (cluster crystals), and the first zeolite-based material to show evidence of metallic conductivity. Other host–guest materials are of interest on account of negative and zero thermal expansion behaviour and the ability to capture and store gases such as H2, NH3 and CO2.
Paul has also demonstrated the use of zeolites as precursor materials for the growth of high quality single-crystal metal and semiconducting nanowires, encapsulated nanoparticles, and as hosts for inorganic electrides and rare alkalide anions. Current work is focussed on the development of light hybrid organic–inorganic frameworks with zeolite-like ion exchange properties, suitable for host–guest chemistry