Catalyst degradation at the cathode of a membrane electrode assembly (MEA) remains a critical issue for practical polymer electrolyte fuel cell (PEFC) operation, but such wet systems impede detailed visualization of degradation events in the cell during its operation. In this work, for the first time, operando spectroimaging (X-ray absorption near-edge structure−computed tomography) was used to produce clear three-dimensional (3D) images of the morphology, Pt and Co distributions, Co/Pt atomic ratio, and Pt valence state of a Pt−Co/C cathode catalyst in a PEFC MEA before and after performing a PEFC-accelerated degradation test. The infographic approach combining the operando spectroimaging and unsupervised learning of the 3D images revealed a catalyst degradation mechanism with different degradation behaviors for Pt and Co in the bimetallic catalyst and negligible migration of the Pt catalyst in local parts of the MEA.

The solid-state dual-ion battery delivers a high reversible capacity of 80 mA h g−1, with long-term cycling stability.

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Silver nanoparticles were prepared with a chemical reduction method in the presence of polyvinylpyrrolidone (PVP) used as a stabilizing agent. During the synthesis of Ag nanoparticles, aqueous silver nitrate solutions were used as the precursors and sodium borohydride was used as the reducing agent. Four Ag-nanoparticle suspensions were prepared with the initial Ag + concentrations of 2, 4, 6, and 8 mM in the corresponding precursors. The in-situ time-resolved small-angle X-ray-scattering (SAXS) technique was used to monitor the nucleation and growth processes of Ag nanoparticles. The particle-size change with time was obtained by analyzing the SAXS data with a tangent-by-tangent method. The SAXS results demonstrate that the Ag nanoparticle growth behaves as a linear relation in the initial growth stage (<1 s), which was used to evaluate the critical particle size. The growth of Ag nanoparticles experienced a fast stage and then a slow stage in their whole formation process. A diffusion−coalescence model has been proposed to describe the growth behavior. The particle size change with growth time can be fitted well by this model. The effect of initial Ag + concentration on the final particle size and the growth mechanism of Ag nanoparticles are discussed in this paper.