Rebecca Buckley
To learn more about the FreeHydroCells research programme, we asked Project Coordinator Dr Ailbe Ó Manacháin a number of questions about the project’s goals, research questions and general work plan.
Q1. The Horizon Europe call topic for FreeHydroCells requested projects that are “high-risk/high return”. In what way does FreeHydroCells meet this criteria with respect to the State-of-the-Art?
A1. To achieve a high return for a viable and novel clean hydrogen production solution, all the present challenges faced by the State-of-the-Art must be targeted in the project, and those challenges are difficult and many. To produce the hydrogen, a threshold in solar energy must reach the redox potential in order to drive it, and for that to happen all the challenges must be sufficiently addressed and then optimised. Given the shear number of challenges faced, and the fact they must all work to achieve the high reward, the project must be deemed as high risk.
Q2. When considering the novel materials to use, what are the deciding factors?
A2. The novel semiconductor materials must have a range of controllable band gaps (~0.3-2.2 eV) and band edge positions (to give band-to-band alignment and alignment to the redox potentials at the surfaces). The control may be from thin film thickness control and/or doping, or other methods such as exploiting Bohr radius interactions. We must be able to deposit the materials using ALD/CVD processes on appropriate surfaces in uniform, continuous films with stable interfaces. The materials must be made in such a way as to have a high conductivity and a low defect density.
Q3. How can the properties be controlled in multi-junction systems using novel emerging materials to make it feasible to produce clean hydrogen from water through solar energy conversion?
A3. We engineer the doping type of each layer to make junction diodes with depletion layers to reduce recombination losses of solar energy, and we align the band gaps and band edges to maximise solar energy absorption. All interfaces, including the surface/water interfaces, are optimised to ensure maximum stability and minimal loss of solar energy.
Q4. What system designs are important for producing and gathering the clean hydrogen in a modular system so that it is suitable for maximum hydrogen production?
A4. A flow/membrane design delivers dynamic water-based electrolyte/ions in a split cassette/rack subsystem design for driving the reduction and oxidation potentials for water splitting with hydrogen production. A hydrogen collection subsystem design is implemented. The modular demonstrator system will be designed geometrically and functionally for optimum hydrogen production at a test system level.
Q5. What things must be considered to ensure the system is suitable for upscaling and commercialisation if successful?
A5. We must ensure the system uses sustainable materials and a simple, water-based, easily-produced, electrolyte. The materials deposition processes must be low-cost upon upscaling, and the fabrication of the modular system must use cheap and sustainable materials with ease of construction. The test system must be suitable to be scaled up, and the system may also be increased through modular addition of system units higher levels of hydrogen production.
Q6. What is the general work plan for FreeHydroCells?
A6. My answers to the previous questions give a hint as to how such an ambitious challenge could be approached. Existing State-of-the-Art photoelectrochemical materials and their integrated systems have not to date produced the Redox Potential levels required to self-drive water splitting to produce clean hydrogen. Solar energy absorption is often too low, and the solar energy that is absorbed can have high losses, so when combined, it deprives the Redox Potential in the water (electrolyte) of the solar energy supply it needs to drive the chemical reactions to produce molecular hydrogen to store the solar energy. A way must then be found to give efficient production in a modular system that has the potential for upscaling and commercialisation. The work plan addresses these challenges by,
A. Applying sustainable emerging materials that may permit fine control of important properties
B. Combining the materials in a way that would address the challenges of achieving water splitting
C. Scientifically engineering the materials system to maximise solar energy absorption
D. Minimising the effect of absorbed solar energy loss mechanisms
E. Optimise the materials/water (electrolyte) interfaces to ensure efficient transfer of solar energy to the redox potential
F. Design and implement a novel flow bath chamber system to maximise hydrogen production and collection
G. Develop an overall system that would be suitable for rapid upscaling and commercialisation
Q7. If successful, how do you envisage it in commercial use and what is the ultimate aim?
A7. In its larger scale form, and similar to the way solar farms are created, the optimum sized photoelectrochemical module can be replicated as much as required and placed adjacent to each other, incrementally increasing the hydrogen production as a function of the number of modules, but with water flow and gas collection separated into sets for separate areas in water delivery and gas storage. In its smallest scale, a single module could be used per household/business for their hydrogen energy needs (e.g. heating, cooling, vehicles, business operations). Intermediate scales could be moderately sized clustered modules in sub-farms to supply housing estates, business parks, villages, clustered-type housing/business premises in general. If successful in creating a stand-alone, self-driven system for splitting water, no input power would be necessary and these would all have the option of off-grid operation anywhere there is sunlight and a water source, fresh or salt water. The far off ultimate aim (or maybe just a dream really), if this work was fully successful, and other activities we have planned in other related areas are fully successful, would be to increase the hydrogen production level 10-100 times from what would be achievable from the outcome of this project. I have a plan on how to achieve it, but that plan remains confidential and lodged in my brain for now…
For more information about FreeHydroCells get in touch at freehydrocells@ucc.ie.
