Develop proper ionic liquids electrolytes which are compatible with diamond structures and can operate at temperatures > 300 °C under concentrated solar radiation.

The development of thermally and electrochemically stable new ILs (and their mixtures) will be pursued. New ILs, based on stable linear and cyclic ammonium, sulfonium and phosphonium cations, which exhibit thermal stability at over 300 °C, will be developed as electrolytes for photoelectrochemical H2 production, as well as for N2 and CO2 reduction, and will be tested for compatibility with the diamond-based electrodes in the PEC reactor. To quantify the performance, a successful validation will be the assessment of their continuous use for at least 48 h at 300 °C during operations.

Fabricate lab-level test versatile setups for evaluating the production of H2.
SPEEDY project aims at providing a reliable chemical reactor to demonstrate the technology at a TRL 2/3. The design and fabrication of such systems will also anticipate their application in the future, to drive the technology towards even higher TRLs after the end of the project activities.

Optimize the functional properties of the active solar-driven black diamond structures for the development of efficient PEC converter.

The combination of all the experimental activities on the engineered materials will be used to define features and recipes suitable for the progress of the proposed structures. The advanced characterisation activities allow optimizing the devices, to be fabricated and tested in a chemical reactor. The performance of the resulting prototypes will be analysed in terms of solar quantum efficiency (i.e., the quantum efficiency over the solar spectrum), Faradaic efficiency, solar-to-electric (ηSE) and solar-to-hydrogen (ηSH) energy conversion efficiency, which are identified as main Figures of Merit (FoM). The success of the project will be measured by obtaining comparable FoM values with respect to those reported in literature for the most advanced state-of-the-art solar-driven PEC converters. Considering the most important published results, we can state that the achievement of the following (minimum) target values is considered proper for enabling a successful validation of the new technology at the declared TRL 2/3 and pushing more research efforts in the technology to higher TRLs in the near future: solar quantum efficiency > 40%; ηSE > 20%; Faradaic efficiency > 60%; ηSH > 10% at 300 suns. However, as reported in Section 1, these values do not represent the ultimate target of SPEEDY, which, according to preliminary calculations performed considering fully optimized conditions, can achieve values of ηSH over 30%, representing a high gain for PEC converters.

Demonstrate the green production of H2 and other chemical fuels by a unique solid-state electrodes’ platform.

Proof-of-Concept (PoC) experiments are performed to demonstrate the production of H2, but also the production feasibility of NH3 and small hydrocarbons in specific catalytic media by using the new diamond-based PECs. Reliability, durability, and production rates are the main recognized FoM for the evaluation of the performance of the prototypes. As described for PO.1, we can identify successful (minimum) target values, which are competitive to the values reported for the most advanced current PEC solar technologies, to properly validate the technology: reliability > 30 cycles of production; durability > 48 h of continuous production; H2 production rate > 40 µmol h-1 cm2.