S C

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1 3 5 I H I G H L I G H T S 2 0 2 2

The simplicity of simultaneous, identical-location SAXS/XRD allows for easy, online data analysis during acquisition, requires no a priori information about the commercial MEA (which is often not available), and places a powerful tool in the hands of non-expert users. The relaxed angular resolution/range requirements necessary for particles of this size permit these SAXS and XRD measurements to be easily obtained at general-purpose hard X-ray beamlines.

In conclusion, high-energy XRD and SAXS are a convenient and robust platform for studying catalyst degradation in situ. Comparison of SAXS and XRD of the Pt nanoparticles allows aggregation to be quantified in real time during accelerated durability tests. In the case of a commercial Pt/C MEA, the catalyst first undergoes a rapid aggregation phase, followed by coalescence of the aggregates and gradual Ostwald ripening into larger domains. Understanding how ageing mechanisms evolve during the catalyst life cycle is critical for designing more stable catalysts and extending the durability of commercial fuel cells.

Fig. 127: a) Pt electrocatalyst particle sizes in the cathode and anode of the

PEMFC during the accelerated stress test, determined by in-situ SAXS

and XRD. b) Structural evolution of the electrocatalyst during cycling, showing how SAXS and XRD probe

distinct but complementary aspects of the nanomorphology.

PRINCIPAL PUBLICATION AND AUTHORS

Decoupling catalyst aggregation, ripening, and coalescence processes inside operating fuel cells, I. Martens (a), R. Chattot (a), J. Drnec (a), J. Power Sources 521, 230851 (2022); https:/doi.org/10.1016/j.jpowsour.2021.230851 (a) ESRF

New advanced design of CO2-philic copolymer membranes for CO2 capture

A new strategy was developed for grafting multi- block (segmented) copolymers, which were characterised using X-ray scattering experiments. Their composition and the number and molecular weight of their CO2-philic grafts were precisely controlled. The grafting induced a specific morphology allowing great improvement of their membrane properties for CO2 capture.

CO2 capture is considered one of the key target objectives for limiting climate change and contributing to global sustainability [1], and a great deal of effort is being made worldwide to develop techniques to achieve this goal. In particular, membranes made from multi-block copolymers with PEO soft blocks are well known for their affinity for CO2, but their CO2 permeability is generally strongly limited by PEO crystallisation for high PEO contents [2-4]. In this work, PEO crystallisation was avoided by a new strategy of multi-block copolymer grafting with CO2-philic soft grafts.

The multi-block copolymer of interest was derived from former work on highly selective membranes for CO2 capture [5] and the new grafted copolymers (Figure 128) were obtained by combining three orthogonal chemistries. First, polycondensation was used for the