Operando spectroscopy of phosphorus species at the Pt electrode/electrolyte interface in HT-PEM fuel cells

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The joint project addresses the fundamental activation and degradation mechanisms at the electrode/electrolyte interface in high temperature polymer electrolyte membrane (HT-PEM) fuel cells. It combines the substantial expertise of three groups in materials synthesis, operando characterization, and electrochemical investigation to advance the detailed understanding of the underlying chemical reaction mechanisms between phosphorus oxoacids and the platinum electrode surface under operating conditions. To do so, the experimental expertise of the German PIs in hard and soft X-ray spectroscopy will be combined and extended by the renowned electrochemistry and fuel cell experience of the Czech group. AG Roth applies its expertise in operando analysis using hard X-ray absorption fine structure (XAFS) analysis at the platinum L2,3-edge to specifically probe how the geometric and electronic structure of the platinum as well as platinum-alloy nanoparticle catalyst changes under operating conditions. AG Bär will make use of its soft X-ray expertise to develop – in close collaboration with AG Roth – an in-situ cell that allows probing of the phosphorus K-edge by near edge X-ray absorption fine structure (NEXAFS) to specifically address changes in the interaction between Pt electrode surface and electrolyte, i.e. phosphoric acid and other phosphorus species of relevance in HT-PEM fuel cell operation. AG Bouzek will utilize the insight from these sophisticated characterization techniques to suggest novel materials as well as optimized operation parameters to reduce poisoning and degradation phenomena in fuel cell systems with phosphoric acid imbibed proton-exchange membranes. In the future, this may help to widely introduce combined heat and power plants (microCHP) based on HT-PEM as a highly efficient and environmentally neutral component of the distributed energy supply based on renewable energy sources.