Polymer semiconductors toward efficient photocatalytic H2 production from sea water - understanding and exploiting the presence of ions
Lead Research Organisation:
Imperial College London
Department Name: Chemistry
Abstract
Global warming, increasing environmental pollution and limited fossil energy resources push our society to develop a more sustainable production and use of energy. Direct solar hydrogen production with suspended particles by photocatalysis offers an effective solution. However, until now, photocatalytic hydrogen evolution (PHE) suffers from limited efficiencies, is often poorly understood and neglects the practically important sea water environments, where performance typically decreases, but where particle based PHE would be most promising. In this project, we will first study ionic effects, induced by presence of sea water ions, on state of the art polymeric semiconductors systematically. Time resolved spectroscopy will provide fundamental insights into photophysical material properties that are affected by the presence of and interaction with the ions. This activity and property study will focus on hydrophilic donor-acceptor (D-A) structures, which were shown to perform very efficiently in a particle bulk heterojunction (BHJ). Next, we will explore photo-activation processes of polymer materials used for organic electrochemical transistors (OECT), which were shown to enhance the charge stabilization and transport properties upon interacting with sea water ions. By this, we will identify promising material candidates for next generation sea water photocatalysts, which we will study as (BHJ) nanoparticles and optimize toward higher PHE efficiencies in presence of ions. Thereby, this project will provide fundamental insights in ionic effects and their influence on the photocatalytic performance of polymer materials, as well as pathways to tune photophysical properties by ionic interactions. Photo-Iono-Catalysis hence presents an important step to make sea water PHE more viable, while shedding light on the possibility to modify material properties by environmental ionic interactions, which are extendable to many other energy conversion processes.
Publications
Aymerich-Armengol R
(2024)
Operando Insights on the Degradation Mechanisms of Rhenium-Doped and Undoped Molybdenum Disulfide Nanocatalysts During Hydrogen Evolution Reaction and Open-Circuit Conditions
in Advanced Functional Materials
Cheng G
(2025)
Photo-Rechargeable Sodium-Ion Batteries with a Two-Dimensional MoSe 2 Crystal Cathode
in Nano Letters
Gouder A
(2023)
Bridging the Gap between Solar Cells and Batteries: Optical Design of Bifunctional Solar Batteries Based on 2D Carbon Nitrides
in Advanced Energy Materials
Sridhar V
(2023)
Designing Covalent Organic Framework-Based Light-Driven Microswimmers toward Therapeutic Applications.
in Advanced materials (Deerfield Beach, Fla.)
Willner B
(2024)
Correlation between the Molecular Properties of Semiconducting Polymers of Intrinsic Microporosity and Their Photocatalytic Hydrogen Production
in Journal of the American Chemical Society
| Description | 1) In the project with NPL, we have shown that THz-TDS can be efficiently used to measure the complex permittivity (i.e. dielectric properties) of carbon nitrides and polymers on time scales corresponding to solar energy conversion (fs-ps). These findings can be translated to other materials. They are highly relevant, since knowledge of complex permittivity on this time scale is critical to understand fundamental photophysical processes in organic semiconductors in context of solar energy conversion, which are so far being estimated by measurements reflecting much slower or much faster time scales (by orders of magnitude off). Aside, we reveal that humid environments can strongly modify and enhance such properties in the THz scale - which is unexpected, and relevant for correct description of internal photo-physical properties enabling solar energy conversion functions in various fields (including photocatalysis, solar cells, and photodetectors e.g.). The initial paper is under revision, and initiated various follow-up projects. These include studies on various metal organic frameworks (MOFs), Covalent organic frameworks (COFs) to establish structure-property relations. 2) We study the influence of salt ions being present in sea water on the process of solar energy conversion for renewable fuel production. So far, it was assumed that they only modify the surface catalytic mechanism and not internal properties. Our findings show that ions can be efficiently used to modify excitonic properties and charge generation within polymer semiconductors, which is a limiting factor in organic materials - if suitable functional groups are present. By enabling volume ionic interactions with glycolation and surfactants, both, the yield of excitons and their lifetime can be strongly increased (>100%), offering unprecedented photophysical tuning possibilities through the environment. Also an ionic influence on charge generation efficiency was found. The manuscript is close to submission. These findings on single materials are being explored further for bulk heterojunctions, where they should enable more efficient photocatalysis due to better exciton migration, leading to generation of more functional charges for solar energy conversion. 3) We performed a systematic study on the influence of porosity and hydrophilicity in polymers for photocatalytic hydrogen production in presence of sacrificial agents (ascorbic acid) with the group of Iain McCulloch(Oxford). By using time resolved spectroscopy, I could elucidate the process kinetics and catalytic mechanism bottleneck: or findings summarize to water adsorption being a crucial metric for performance in photocatalysis, rather than surface area estimated traditionally by Ar or N2 sorption. Combining high surface area with wettability yields optimal performance since both enable fast exciton and charge reactions in the volume of photocatalytic particles. These findings are key also for my UKRI project, since they elucidate how to enable property changes and boosted environmental interactions within photoabsorber materials - which was not achievable within solid inorganic systems before. 4) In a study on photocatalytic hydrogen evolution with the MOF MIP-177, color changes and charge accumulation have been observed upon extended illumination. I supported this project through my experience on photobatteries and dark photocatalysis, enabling us to use this material for triggered hydrogen production in the dark (using solar energy in a time-delayed way), and to elucidate the respective photophysical properties (supervising a PhD student's project). Optimizing conditions, I could show with our MOFs the highest yield of time delayed hydrogen production reported so far. The work is close to submission. Several follow-up projects developed from this, in which I take a leading role. 5) Supporting the group of Cecilia Mattevi (Materials Dep., Imperial) on photobattery works, I could help elucidating light driven ionic processes in MoSe2, and establish a functional description of a photobattery that works with Na ion technology and can be charged purely by indoor LED light. While not being anticipated originally in my proposal, this work is pivotal for future technologies on controlling light driven ionic and photocharging, which is part of my future career. Follow-up projects are initiated and co-supervised by me. |
| Exploitation Route | 1) Our finings broadcast the suitability of THZ-TDS for characterization of photophysical properties on time scales relevant to solar energy conversion processes (fs-ps). They enable to extract physical parameters that are crucial for exciton stabilization and separation, while providing insights on how comparable different experimental conditions are, and how they actually modify material properties. This research is fundamental for enabling more photophysical property knowledge on difficult-to-characterize organic semiconductor materials, while closing the so-called THz-gap. Applications span from photocatalyis over solar cells to photodetectors and LEDs, since function of all of them relies on complex permittivity and and separation/recombination properties of excitons or charges. 2) Our findings on ionic tuning of internal photophysics (excitons and charges) are crucial for the advancement of photocatalysis working efficiently in natural (sea water) conditions, where ions are always present. Hence, they will contribute to a longer line of research in future, and likely influence the entire field of organic photocatalytic solar fuel production in general. They are further relevant to the fields of optical sensors and optoelectronics, ad well as possibly ionotronics in future. 3) Having shown that wettability is a key subfactor of porosity for photocatalytic performance, and how ions can be made interact with organic matter through side chain and surfactant engineering, is pivotal for the entire field of functional organic materials' applications. Tuning emissive properties helps generating sensors (especially operating with PL emission) and can advance diode technologies. It's key for the emerging field of optoionics, where photo-effects are coupled to functional material property modifications. 4) The works on photobatteries and photocharging MOFs are key to enable more efficient materials that internally combine light absorption and charge storage properties. They enable novel photobatteries, sensors, memristors and other technologies, as I have shown in the past and patented before coming to Imperial. The structure-activity-relationships made, on abundant and robust systems, are highly relevant in order to establish new technologies that decouple the variability of sunlight from its use on demand. |
| Sectors | Chemicals Digital/Communication/Information Technologies (including Software) Electronics Energy Environment Healthcare |
| Description | Complex permittivity characterization by Therahertz Time Domain Spectroscopy with NPL |
| Organisation | National Physical Laboratory |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | We synthesized the materials used for this projects, trained a master student on material preparation and processing, and prepared samples for the THz-TDS measurements. Characterization by XRD and UV-VIS is also carried out at ICL. We commonly supervise the project, and we lead the publication preparation proces. Also, we provide transient pump-push spectroscopy to measure exciton and charge generation related to photophysical findings made by THz-TDS at NPL. |
| Collaborator Contribution | The partners at NPL provide as setup for THz-TDS and assist in the measurements of the material. They trained a common master student to do the analysis on its own. Besides, they help with data analysis and manuscript writing. Another partner at NPL provided He-Pycnometry measurements for density characterization. |
| Impact | The collaboration is multidisciplinary, involving chemists, physicists and material scientists. |
| Start Year | 2022 |
| Description | Organic material synthesis and photocatalytic activity characterization in Oxford |
| Organisation | University of Oxford |
| Department | Department of Chemistry |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | At Imperial College London, we synthesise nanoparticles from the polymers provided from collaborators in Oxford. Our main work is photophysical characterization by means of transient absorption and photoluminescence spectroscopy, to explain the influence if ionic (or other) environments on the materials' photophysics and their modification. The collaboration also includes such characterization of other organic based materials for projects led by the group in Oxford, where we are contributing authors. |
| Collaborator Contribution | We study materials for photocatalytic water reduction. Our measurements at ICL explain how efficiently excitons are generated, how then transition to charges, and how long these live - which is crucial for energy conversion function. We study lifetimes of all species, on different length scales, to explain the efficiency of solar energy conversion process, while comparing similar materials with different chemical functionalizations for better understanding of chemical design influence factors. |
| Impact | The collaboration is multidisciplinary, involving chemists and physicist. We compare chemical design factor and reactions with the environment to photophysical properties. The research is relevant for all sectors studying solar energy conversion with organic based materials. |
| Start Year | 2022 |
| Description | CPE Solar [and Electro] Fuels Workshop |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | At the CPE Solar and Electro Fuels Workshop, we had the opportunity to present our research focused on "Exploring the Impact of Interfaces and Environmental Factors on Water Oxidation Kinetics in Metal Oxides." The audience, primarily consisting of PhD students, showed great engagement with the topic. This presentation aimed to show several ways in which interfaces and environmental variables influence the efficiency and kinetics of water oxidation processes in metal oxides, a critical reaction for the production of solar fuels. The engagement of the audience highlighted the relevance and interest in understanding these complex interactions. This workshop served as a platform for sharing cutting-edge research and fostering discussions among emerging scientists about the challenges and opportunities in the development of more efficient solar fuels systems |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.imperial.ac.uk/events/167387/cpe-workshop-on-solar-fuels/ |
| Description | Chemistry and Materials Discovery Day at The Invention Room |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | We participated in a family-friendly discovery day at The Invention Rooms, engaging between 50-100 children (ages 5-11) and their families in interactive activities on energy and hydrogen. Through hands-on demonstrations, we sparked curiosity about sustainable energy solutions, making complex concepts accessible and fun. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Delegate to bilateral meeting of the Royal Society and Berlin-Brandenburg Academy of Sciences on: Expectations of chemistry for a sustainable World |
| Form Of Engagement Activity | A formal working group, expert panel or dialogue |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Approx. 60 attendees from the Royal Society and the German Berlin-Brandenburg Academy of Sciences including invited guests met to discuss research directions, promising possibilities and collaboration efforts in order to advance research in chemistry for a more sustainable world. This included talks and discussions, resulting ultimately in policy incentives via the respective funding bodies in Germany and the UK. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Engagement with Local Community: Materials and Molecules Discovery Day |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | Parents and Children living in White City joined the Materials and Molecules Discovery Day we organized in Imperial Facilities in White City. It sparked interest for natural sciences, sustainable materials for energy conversion, and the production of renewable fuels. |
| Year(s) Of Engagement Activity | 2024 |
| URL | https://www.imperial.ac.uk/white-city-campus/community/staff-students/public-engagement/ |
| Description | Future Energy Festival 2023 |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | During this event, we contributed by "Shining a Light on Materials for Solar Energy Conversion." Our stand aimed to explain our research on green hydrogen to the general audience, explaining in layperson's terms how we utilize spectroscopy to investigate the process of water splitting. By breaking down complex scientific concepts into more understandable content, we sought to engage and educate the public on the importance of solar energy conversion and its potential to provide a sustainable source of green hydrogen. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.imperial.ac.uk/events/164378/save-the-date-energy-futures-lab-future-energy-festival-202... |
| Description | Great Exhibition Road Festival |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | In collaboration with architecture firm Cookies, we showcased the benefits of developing durable cement through green methods that significantly reduce CO2 emissions. Throughout the day, a series of workshops were organized, engaging children aged 5 to 15 in the hands-on activity of molding various shapes using this "green cement." This interactive experience provided a practical understanding of the material's environmental advantages. The initiative aimed to foster awareness among the younger generation about sustainable building materials and their critical role in protecting the environment. The workshops sparked curiosity among participants about sustainable practices in construction. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.greatexhibitionroadfestival.co.uk/event/down-earth/?backto=whats-on |
| Description | Materials Horizons 10th Anniversary 'Community Spotlight' blog article for Meet our Emerging Investigators - invited contribution |
| Form Of Engagement Activity | A magazine, newsletter or online publication |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | Interview on my research, inspiration and interests, including suggestions to early career researchers |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://blogs.rsc.org/mh/2023/11/21/materials-horizons-community-spotlight-introducing-our-emerging-... |
| Description | Presentation at the RSC Photophysics and Photochemistry Group Early Career Meeting 2023 Glasgow, United Kingdom |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Teh presentation sparked discussions about environmental factors being able to influence internal photophysical properties of organic materials. It helped to provide brader understanding on why photocatalysis in sea water conditions may lead to different activities than in clean water. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.rsc.org/events/detail/76891/rsc-photophysics-and-photochemistry-group-early-career-meeti... |
| Description | Public talk at Future Energy Festival for broad audience from UK and London |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | approx. 100 people of diverse backgrounds attended the talk in the Future Energies Festival. It sparked discussions about future possibilities to balance renewable energy supply by photo-battery concepts. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.imperial.ac.uk/events/164378/save-the-date-energy-futures-lab-future-energy-festival-202... |
| Description | Talk at E-MRS Fall meting 2023 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Presentation at international research conference with subsequent discussions with the audience. Thsi resulted in potential development of future collaborations. |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.european-mrs.com/meetings/2023-fall-meeting |