Periodic Reporting for period 1 - PH2OTOGEN (ACCELERATION OF PHOTOCATALYTIC GREEN HYDROGEN PRODUCTION TO MARKET READINESS THROUGH VALUE-ADDED OXIDATION PRODUCTS)
Reporting period: 2024-01-01 to 2025-06-30
The PH2OTOGEN project aims at generating solar hydrogen through a photocatalytic reaction. Whilst most research on photocatalytic hydrogen generation focusses on the splitting of water to form hydrogen and oxygen, PH2OTOGEN aims to couple hydrogen generation with oxidation of an organic molecule, such as glycerol oxidation to 1,3-dihydroxyacetone (DHA), in place of oxygen formation. There are several advantages to this approach: i. it avoids the concomitant production of hydrogen and oxygen, which can result in a formation of an explosive mixture; ii. since the products are in different states - hydrogen (gas) and DHA (oil), they can be easily separated without the need for specially engineered membranes; iii. DHA is around 50 times more valuable than the glycerol starting material and therefore provides another possible revenue stream from the device and accelerating the introduction of green hydrogen to the market.
Specifically, the project will develop two types of efficient light-absorbing semiconductor materials: i. a hydrogen evolving particle, ii. an oxidising particle, by testing candidate materials' efficiency and stability on the laboratory scale. These tests will be coupled with advanced analysis that will provide insights into degradation mechanisms and allow the identification of countermeasures to solve these issues. The particles will be deposited on a novel transparent, conductive, porous support (developed by PH2OTOGEN partners) to allow electronic (electrons and holes) transfer between the two particle types. The synthesis of most promising materials will be scaled up and tested outdoors in a 500 cm2 device, with a target of 5% solar to hydrogen efficiency. The technical studies will be coupled by a lifecycle and technoeconomic assessment, which along with performance data, will be used to decide the most promising materials for scale-up and will provide the basis to build a business case.
The technology readiness level (TRL) is expected to increase from 2-3 to 5 at the end of the project (June 2027). The overall device contributes to the production of green fuels and chemicals towards the development of a sustainable society that can mitigate climate change.
Specifically, the project will develop two types of efficient light-absorbing semiconductor materials: i. a hydrogen evolving particle, ii. an oxidising particle, by testing candidate materials' efficiency and stability on the laboratory scale. These tests will be coupled with advanced analysis that will provide insights into degradation mechanisms and allow the identification of countermeasures to solve these issues. The particles will be deposited on a novel transparent, conductive, porous support (developed by PH2OTOGEN partners) to allow electronic (electrons and holes) transfer between the two particle types. The synthesis of most promising materials will be scaled up and tested outdoors in a 500 cm2 device, with a target of 5% solar to hydrogen efficiency. The technical studies will be coupled by a lifecycle and technoeconomic assessment, which along with performance data, will be used to decide the most promising materials for scale-up and will provide the basis to build a business case.
The technology readiness level (TRL) is expected to increase from 2-3 to 5 at the end of the project (June 2027). The overall device contributes to the production of green fuels and chemicals towards the development of a sustainable society that can mitigate climate change.
The reporting period of the project has been focussed on the benchmarking of semiconducting particles, their corresponding charge transport layers and co-catalysts, for both the hydrogen evolution reaction and glycerol oxidation reaction to 1,3 dihydroxyacetone (DHA). For the hydrogen evolving particle, WSe2 and organic semiconductors were studied and the organic semiconductors were found to generate promising photocurrents (> 4 mA cm-2) under sacrificial conditions, which was found to be highly dependent on the charge transport layers used. In parallel, various MoSx-based co-catalysts are under development, with a focus on performance and transmittance, and these are being combined with the organic semiconductors as a next step. For the glycerol oxidation reaction, BiVO4, BiW2O6, MoS2 and organic semiconductors were tested. So far, BiVO4 has been found to be the most promising semiconductor for glycerol oxidation in terms of photocurrent (3.4 mA cm-2) and onset potential. Selectivity to DHA was found to be > 50%, getting close to our final target of 70%. In order to improve the selectivity we are modifying BiVO4 with dopants and optimising the surface.
The semiconducting particles will be deposited on a transparent conducting porous support (TPCS) based on a fluorine-doped tin oxide coated quartz felt that has been developed in a previous EU-funded project, Sun-To-X. The porosity of the substrate allows us to deposit thin layers to maximise light absorption by the semiconductor. Work has focussed on improving the conductivity, transparency and mechanical stability. The maximum weight that can be borne by the substrate has been increased from 25 to 135 grams through optimising loading, density, and annealing temperature. The process methods have been scaled so the TPCS can now be produced on a 100 cm2 scale.
To support the optimisation of the device design, a zero-dimensional model of various reactor configurations has been prepared. This will later be developed in a multi-scale model that will provide information on how to optimise parameters to maximise light transfer, heat transport, charge transport, mass transport and fluid-flow dynamics. The first photoreactor prototypes have been built on a small scale to allow testing of reactor material compatibility with the electrolytes and identification of any flow problems e.g. gas collection pockets. The design has been refined and a piping and instrumentation diagram (P&ID) has been prepared for the final demonstrator.
Finally, an inventory of materials has been prepared for use in TEA and LCA studies. These studies have shown that, out of the candidate materials, the organic semiconductors result in the lowest manufacturing costs of the photocatalytic sheets. The results of these studies will be complementary to performance and stability data in choosing the most promising materials for eventual integration into the reactor. A market study is also on-going and we have found that the co-production of DHA strongly contributes to economic feasibility, however, due to the limited market size of DHA, it would be interesting to expand PH2OTOGEN technology to other glycerol oxidation products to expand the applicability of the device.
The semiconducting particles will be deposited on a transparent conducting porous support (TPCS) based on a fluorine-doped tin oxide coated quartz felt that has been developed in a previous EU-funded project, Sun-To-X. The porosity of the substrate allows us to deposit thin layers to maximise light absorption by the semiconductor. Work has focussed on improving the conductivity, transparency and mechanical stability. The maximum weight that can be borne by the substrate has been increased from 25 to 135 grams through optimising loading, density, and annealing temperature. The process methods have been scaled so the TPCS can now be produced on a 100 cm2 scale.
To support the optimisation of the device design, a zero-dimensional model of various reactor configurations has been prepared. This will later be developed in a multi-scale model that will provide information on how to optimise parameters to maximise light transfer, heat transport, charge transport, mass transport and fluid-flow dynamics. The first photoreactor prototypes have been built on a small scale to allow testing of reactor material compatibility with the electrolytes and identification of any flow problems e.g. gas collection pockets. The design has been refined and a piping and instrumentation diagram (P&ID) has been prepared for the final demonstrator.
Finally, an inventory of materials has been prepared for use in TEA and LCA studies. These studies have shown that, out of the candidate materials, the organic semiconductors result in the lowest manufacturing costs of the photocatalytic sheets. The results of these studies will be complementary to performance and stability data in choosing the most promising materials for eventual integration into the reactor. A market study is also on-going and we have found that the co-production of DHA strongly contributes to economic feasibility, however, due to the limited market size of DHA, it would be interesting to expand PH2OTOGEN technology to other glycerol oxidation products to expand the applicability of the device.
The PH2OTOGEN project aims to develop highly efficient materials for photocatalytic production of green hydrogen and 1,3 dihydroxyacetone (via oxidation of glycerol), targeting 5% solar-to-hydrogen efficiency in a 500 cm2 demonstrator. Although larger size demonstrators have already been built (in particular the 100 m2 system with a 0.76% solar-to-hydrogen efficiency described in Nature volume 598, pages 304–307 (2021) for photocatalytic water splitting), the goal of PH2OTOGEN is to achieve higher efficiencies in a scalable photoreactor to move a step forward to economic feasibility. Furthermore, the replacement of the oxygen evolution reaction (OER) by the glycerol oxidation reaction (GOR) is expected to accelerate the progress to market by providing two revenue streams from the photocatalytic sheets.
In terms of material development, the PH2OTOGEN project is moving beyond the conventional substrates, such as transparent conducting oxide-coated glass, towards transparent conducting porous supports based on fluorine-doped tin oxide coated quartz felts. The use of the felts minimises charge transport and ionic transport resistance, allowing the preparation of large area substrates with minimum performance loss upon scaling. The project is developing novel semiconductor, co-catalyst and charge transport layer combinations which can be deposited onto the porous substrates through scalable processes. System modelling, technoeconomic and lifecycle assessment will be used to guide material choices to maximise economic feasibility and minimise environmental impact.
In terms of material development, the PH2OTOGEN project is moving beyond the conventional substrates, such as transparent conducting oxide-coated glass, towards transparent conducting porous supports based on fluorine-doped tin oxide coated quartz felts. The use of the felts minimises charge transport and ionic transport resistance, allowing the preparation of large area substrates with minimum performance loss upon scaling. The project is developing novel semiconductor, co-catalyst and charge transport layer combinations which can be deposited onto the porous substrates through scalable processes. System modelling, technoeconomic and lifecycle assessment will be used to guide material choices to maximise economic feasibility and minimise environmental impact.