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D3.3 Membrane-electrode assembliesintegration - Executive Summary

Half-membrane-electrode assemblies (MEAs) based on transparent bipolar membranes (TBM) and copper and silver-based cathodic catalysts were prepared and tested in electrochemical cells for validation and further integration in the tandem photoelectrocatalytic reactor (TPER) of the project. The preparation of the MEA entailed the use of different techniques based on: (i)the direct deposition of the catalytic layer (CL) as inkonto the membrane (catalyst coated membrane method, CCM) by either decal method or air-brushingand the following hot-pressing of a gas diffusion layer (GDL);(ii) the preparation of a gas diffusion electrode (GDE) and its subsequent hot-pressing.

CNRS optimised the CCM method based on decal transfer, allowing a controlled and reproducible deposition of the CL on the proton exchange layer of the TBM, followed by a further step of GDL hot-pressing. The instability of the Cu(I) catalyst in the acidic conditions of the PELandin ILs-electrolyte in the POLITO cell testswashighlighted, leading to further development of silver-based catalysts and further electrochemical tests.

POLITO also developed MEAs directly depositing the CL onto the TBM by air-brushing technique. Such assemblies were characterised in afuel cell-type reactor in a two-electrode configuration,demonstrating the target current density of the project. The stability of the required potential was guaranteed for at least 30 min. The carbon-based GDL promotedproton generation and hydrogen evolution in competition with CO2reduction.Therefore, its replacement with fluorine-doped tin oxide (FTO) coated titanium mesh wasconsidered.Itled to alower potential to achieve the target current density of the project (-20 mA cm-2).However,instability ofthe catalyst layer deposited on the Ti-mesh was evidenced;therefore,further investigation is needed to optimisethe materials and electrolytes used.