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.

Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs.

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The crystallization process of noncrystalline Ni–P nanoparticles could be evaluated quantitatively through the standard deviation of ΔR/R from XAFS spectra of P.

The cationic polymerizations of isobutylene (IB) initiated by the H2O/TiCl4 in dichloromethane (CH2Cl2) at −30 °C were carried out in the absence and presence of various external electron pair donors (EDs). Controlled polymerization with a slow polymerization rate and a narrow molecular weight distribution (MWD, M w/M n = 1.11−1.28) of the polymer was achieved by using certain appropriate H2O/TiCl4/ED systems. The kinetics of the IB polymerization with the H2O/TiCl4/ED initiating system was investigated. It indicated that the polymerization rate was first-order with respect both to monomer and to initiator concentrations in the presence of strong or weak EDs. Polymerizations exhibited a second-order dependence on TiCl4 concentration in those cases where weak EDs, such as methyl acetate (MAC), methyl acrylate (MA), sulfolane (HDF), or methyl benzoate (MB), were used. On the other hand, first order in TiCl4 concentration was observed when strong EDs, such as dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), pyridine (Py), or triethylamine (TEA), were used.