Polymer photocatalysts
Lead Research Organisation:
University of Liverpool
Department Name: Chemistry
Abstract
Photocatalytic water splitting has been investigated for many years as a sustainable source of hydrogen production. Until recently research has focused almost exclusively on inorganic materials such as TiO2 . However in 2009 Wang and co-workers showed graphitic carbon nitride was capable of visible light driven hydrogen production under sacrificial conditions . Since then a new area of organic materials for photocatalytic hydrogen production has emerged including a variety of graphitic nitride derivatives , , , covalent organic frameworks , , conjugated microporous polymers , and linear polymers , . This class of materials are particularly interesting due to their robustness, non-toxicity and high visible light activity.
Following on from the work by Sprick et al this project will investigate approaches to overcoming some of the problems present in the polymer photocatalysts. For instance, the most active dibenzothiophene sulfone bearing polymer is insoluble in common organic solvents and so processability in terms of making films or different macrostructures is severely limited. Similarly the hydrophobicity of the polymers is thought to limit dispersion and thus the active catalytic surface. Modification to both the polymer units and microstructure will be undertaken with the aim of improving hydrogen production performance and to move towards a non-sacrificial system.
Following on from the work by Sprick et al this project will investigate approaches to overcoming some of the problems present in the polymer photocatalysts. For instance, the most active dibenzothiophene sulfone bearing polymer is insoluble in common organic solvents and so processability in terms of making films or different macrostructures is severely limited. Similarly the hydrophobicity of the polymers is thought to limit dispersion and thus the active catalytic surface. Modification to both the polymer units and microstructure will be undertaken with the aim of improving hydrogen production performance and to move towards a non-sacrificial system.
People |
ORCID iD |
| Andrew Cooper (Primary Supervisor) | |
| Catherine Aitchison (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509693/1 | 01/10/2016 | 30/09/2021 | |||
| 1795052 | Studentship | EP/N509693/1 | 01/10/2016 | 31/03/2020 | Catherine Aitchison |
| Description | We have developed a method to improve the micro-structure of polymer photocatalysts. Most organic photocatalsysts are powders made up of bulk micron scale particles. In order to improve the surface area to volume ratio of these catalysts it would be beneficial to process the materials into more optimal morphologies such as nanoparticles or films. However many of our most promising polymer photocatalysts are insoluble in common organic solvents meaning that normal methods of post-synthesis processing such as nanoprecipitation and spin coating are not feasible. Instead we have investigated the use of emulsion polymerisation to create nanoparticle analogues of some of our most promising photocatalsysts. This method utilises the monomers solubility in an organic solvents such as toluene to create an emulsion of monomer droplets in water. After sonication and heating Suzuki polymerisation occurs within the confines of the toluene droplet creating a size limited polymer particle. The increased surface area of the emulsion derived particles gives them improved photocatalytic activity for hydrogen production from water in comparison to the bulk materials. We have synthesised and tested a series of these materials and found the hompolymer of dibenzothiophene sulfone has a particularly high activity when synthesised under emulsion conditions, giving one of the best hydrogen evolution rates for an organic photocatalysts in literature. In addition we have developed an organic photocatalyst based on an hydrogen-bonded organic framework. This was shown to be highly active for photocatalysis and is the first example of a molecular material with significant hydrogen evolution rate. The activity of the material was found to be highly dependant on it's crystal packing as an amorphous sample has 200 times lower activity. |
| Exploitation Route | The general method of emulsion polymerisation may be used for a number of different polymer photocatalysts developed by different groups to improve micro-structure and aid activity. In addition the small size of the emulsion derived particle makes them ideal candidates for fabricating hybrid materials which may be capable of overall water splitting. For example the emulsion particles could be combined with an inorganic oxygen evolution photocatalyst to create a nanocomposite which would provide a Z-scheme approach to hydrogen and oxygen evolution. The investigation into a hydrogen-bonded organic framework represents a new class of materials that can act as hydrogen production photocatalysts. This considerably widens the field as it indicates molecular materials as well as polymers could be highly active for this reaction. In addition the relationship between activity and crystal structure has been proved to be crucial to photocatalytic activity and should be taken into consideration when designing further photocatalysts. |
| Sectors | Chemicals,Energy |
| URL | https://chemrxiv.org/articles/Photocatalytic_Proton_Reduction_by_a_Computationally_Identified_Molecular_Hydrogen-Bonded_Framework/11341850https://pubs.rsc.org/en/content/articlelanding/2019/ta/c8ta11383a#!divAbstract |
| Description | Royal Society of Chemistry Travel Grant for PhD Students and Early Career Scientists (For attendance and presentation at ACS Fall national meeting) |
| Amount | £800 (GBP) |
| Funding ID | T19-3923 |
| Organisation | Royal Society of Chemistry |
| Sector | Charity/Non Profit |
| Country | United Kingdom |
| Start | 08/2019 |
| End | 08/2019 |
| Description | Travel Grant - (for attendance and presentation at ACS national meeting) |
| Amount | £500 (GBP) |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Department | SuperSolar Hub |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 08/2019 |
| End | 09/2019 |
| Description | Travel Grant - (for attendance and presentation at artificial photosynthesis Faraday discussion) |
| Amount | £100 (GBP) |
| Funding ID | T19-1415 |
| Organisation | Royal Society of Chemistry |
| Sector | Charity/Non Profit |
| Country | United Kingdom |
| Start | 03/2019 |
| End | 03/2019 |
| Description | Spectroscopic study of small molecules as hydrogen evolution photocatalysts |
| Organisation | Imperial College London |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | I have prepared a series of materials for spectroscopic testing. The dimer and trimer of dibenzothiophene sulfone were synthesised along with the homopolymer loaded with various amount of palladium. I also investigated the performance of these materials for hydrogen evolution reaction from water under sacraficial conditions using a series of photocatalytic tests. |
| Collaborator Contribution | Our partners at Imperial College London, performed transient absorption spectroscopy and photoinduced absorption spectroscopy measurements on the materials we provided. These tested aimed to probe the excited state of the materials. The signal lifetime and amplitude of the excited states was investigated and using both slow and fast TAS and the behaviour of the materials under constant illumination was investigated using PIAS to measure the accumulation of excited state species. |
| Impact | All materials tested were found to have excited state species by TAS. These signals assigned to excitons and charge separated species have been measured.The hydrogen evolution activity of the oligomeric materials increased dramatically with chain length and was sensitive to palladium loading amount. Photocatalytic activity was found to scale well with the TAS signal amplitude. A paper on these oligomeric materials as hydrogen evolution photocatalysts is in preparation and will include the TAS measurements. The PIAS measurements are ongoing and will be included in a further paper. |
| Start Year | 2017 |