Elucidation of Confined Catalytic Sites and Adsorption Intermediates in Crystalline Porous Structures for Renewable Ammonia Reactions

In order to keep pace with the accelerating economic development, and simultaneously achieving sustainable environment, renewable energy sources are highly demanded to replace depleting fossil fuels, as well as green chemicals to substitute with hazardous substances such as non-degradable polymers.

It was found that hydrogen is a promising renewable energy source adopted in fuel cells and an indispensable reactant for synthesizing chemicals in green chemistry.

To generate tones of hydrogen for large scale application, researchers are still investigating effective production procedures.

Considering products of various suggested chemical reactions, as well as limitations on storage and transportation, ammonia is found to be a superior environmentally friendly source for green hydrogen via decomposition reaction.

There has been complete and advanced production, storage and transportation methodologies for ammonia; ammonia also has the advantage of high hydrogen density; and during its decomposition, no COx compound is released.

Based on previous studies, during endothermic decomposition, catalysts with porous structures play essential roles in reducing activation energy and creating milder reaction conditions (ie. lower temperature and pressure) which saves energy.

High turnover frequencies, via either classical lewis pairs (CLP) or frustrated lewis pairs (FLP) formed by catalysts, can also be achieved. The research on optimization of catalysts for ammonia reactions is still ongoing.

For effective sustainable hydrogen generation with applications in fuel cells and green chemistry, the project will therefore investigate catalysts in ammonia decomposition under the supervision of Prof. Edman Tsang at University of Oxford.

Catalysts fell into research are dominantly zeolites/metal-organic frameworks (MOFs) of diverse types. (Other ammonia-organic reactions may also be tested on catalysts if time is allowed.) This project is interested in the behaviors of catalytic sites and adsorption intermediates during the process, by controlling the degree and type of metal atoms and porous support with specific charge distribution in a confine nano-space and attempting to justify catalytic mechanisms involved.

Meanwhile, we aimed to find better design of catalysts to increase catalytic sites for higher conversion efficiency and to eliminate the use of scarce elements such as ruthenium.

In the project, it is important to collect high quality diffraction data during catalytic testing and carry out in-situ monitoring of species to investigate reactions. Thus, we aim to conduct systematic in-situ studies at beamline I11 for selected catalytic reactions.

With recent advancement in the instrumental sensitivity of the synchrotron technique using the in-situ gas cells coupled with online mass spectrometer, the unique experimental setting will provide a competitive edge in this area. Dimond light source is the co-founder of this project. Dr Sarah Day and Professor Chiu Tang of I11, who have direct expertise in SXRD will act as main supervisors at Diamond.

It is also helpful to locate H2 in the structure to complement the SXPD work, hence we plan to gain access to use NPD facilities too (e.g. Polaris or HRPD at ISIS). In addition, other in situ techniques i.e. APXPS (Prof. Held, B07) and in situ XAS (Dr Cibin, B18) will be applied to support results.

To conclude, the project focuses on elucidation of catalytic behviours and optimization of catalysts for ammonia reactions, for the purpose of generating sustainable hydrogen gas involved in proton-exchange fuel cell and green chemistry cycles. This project falls within the EPSRC 'Energy and Decarbonisation' research area.