Advanced catalysts for proton exchange membrane water electrolyzers (PEMWE)

Involved researchers: Darius Hoffmeister, PhD student.

Although PEMWE is regarded as the most promising type for renewable energy conversion application, its widespread application is still hindered. The reasons are lying on both high investment cost (CAPEX) and operating cost for H₂ production (OPEX), which make the green hydrogen uncompetitive with grey H₂. Regarding the CAPEX, the catalysts cost has recently become the major cost factor as the price of precious metal i.e. iridium drastically increases lately. These two major hindrances could be partially mitigated by developing and implementing an efficient OER catalyst, which could reduce precious metal loadings and the energy consumption of PEMWEs.

Advanced catalysts for proton exchange membrane water electrolyzers (PEMWE) — TEM images of IrO2@TiO2 catalyst particle and TiO2 precursor particle (left) and polarization curves of PEM electrolyser using IrO2@TiO2 catalyst in comparison with IrO2 commercial catalyst. Pham et. al., Appl. Catal. B, 269 (2020) 118762

To address the aforementioned issue, in our team, we are developing advanced structured catalysts based IrO₂ and TiO₂ nanostructured materials. Example of this structured catalyst is IrO₂@TiO₂ core-shell particles (see right Figure). We developed a synthesis method to obtain scalable batch of the IrO₂@TiO₂ core-shell catalyst. The synthesis process is based on impregnation method with precursors – support interaction. Catalyst layers are prepared by spray coating the synthesized catalysts onto titanium porous transport layers (Ti-PTL) to form porous transport electrodes (PTEs). The IrO₂@TiO₂ catalyst showed a superior performance compared to the unsupported IrO₂and mixed IrO₂/TiO₂ commercial catalysts (see Figure). Our IrO₂@TiO₂ catalyst also enables implementation of low Ir-loading catalyst layers of 0.4 mg_Ir cm^-2 for PEMWE without compromising the cell performance. We are now working on further advancing this catalyst concept toward a comprehensive cell performance and stability goal and evaluating its industrial applicability. The work is in close collaboration with renown institutes and industrial partners. It is funded by the Federal Ministry of Education and Research of Germany (BMBF) in framework of StacIE project.