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Transmission electron microscopy went through a revolution enabling routine cryo-imaging of biological and (bio)chemical systems, in liquid form. Yet, these approaches typically lack advanced analytical capabilities. Here, we used atom probe tomography to analyze frozen liquids in three dimensions with subnanometer resolution. We introduce a specimen preparation strategy using nanoporous gold. We report data on 2- to 3-μm-thick layers of ice formed from both high-purity deuterated water and a solution of 50 mM NaCl in high-purity deuterated water. The analysis of the gold-ice interface reveals a substantial increase in the solute concentrations across the interface. We explore a range of experimental parameters to show that atom probe analyses of bulk aqueous specimens come with their own challenges and discuss physical processes that produce the observed phenomena. Our study demonstrates the viability of using frozen water as a carrier for near-atomic–scale analysis of objects in solution by atom probe tomography.

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This study focuses on the synthesis of FeRh nanoparticles via pulsed laser ablation in liquid and on controlling the oxidation of the synthesized nanoparticles. Formation of monomodal γ-FeRh nanoparticles was confirmed by transmission electron microscopy (TEM) and their composition confirmed by atom probe tomography (APT). For these particles, three major contributors to oxidation were analysed: (1) dissolved oxygen in the organic solvents, (2) the bound oxygen in the solvent and (3) oxygen in the atmosphere above the solvent. The decrease of oxidation for optimized ablation conditions was confirmed through energy-dispersive X-ray (EDX) and Mössbauer spectroscopy. Furthermore, the time dependence of oxidation was monitored for dried FeRh nanoparticles powders using ferromagnetic resonance spectroscopy (FMR). By magnetophoretic separation, B2-FeRh nanoparticles could be extracted from the solution and characteristic differences of nanostrand formation between γ-FeRh and B2-FeRh nanoparticles were observed.

The worldwide developments of electric vehicles, as well as large-scale or grid-scale energy storage to compensate the intermittent nature of renewable energy generation has generated a surge of interest in...

Fuel cells recombine water from H2 and O2 thereby can power, for example, cars or houses with no direct carbon emission. In anion‐exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen‐reduction reaction occurs. However, the sluggish kinetics of the hydrogen‐oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, the authors observe an unexpected ingress of B into Pd nanocatalysts synthesized by wet‐chemistry, gaining control over this B‐doping, and report on its influence on the HOR activity in alkaline conditions. They rationalize their findings using ab initio calculations of both H‐ and OH‐adsorption on B‐doped Pd. Using this “impurity engineering” approach, they thus design Pt‐free catalysts as required in electrochemical energy conversion devices, for example, next generations of AEMFCs, that satisfy the economic and environmental constraints, that is, reasonable operating costs and long‐term stability, to enable the “hydrogen economy.”

Nanoporous gold (NPG) is usually made by electrochemical dealloying of Ag from binary AgAu alloys. The resulting nanoscale ligaments are not very stable, and tend to coarsen with time by surface self-diffusion, especially in electrolyte, which may lead to inferior electrocatalytic properties. Addition of a small amount of Pt to the precursor alloy is known to refine and stabilize the nanoporous product (NPG-Pt). However, the mechanisms by which Pt serves to refine the microstructure remain poorly understood. The present study aims to expand our knowledge of the role of Pt by examining NPG-Pt at atomic resolution with Atom Probe Tomography (APT), as well as by aberration-corrected Transmission Electron Microscopy. Atomic level observation of Pt enrichment on ligament surfaces sheds light on the underlying mechanisms that give rise to Pt's refining effect. Owing to improved Ag retention with higher Pt content, NPG-Pt (made by dealloying AgAuPt) was shown to have the highest surface area-to-volume ratio, compared to NPG-Pt (made by dealloying AgAuPt). Quantitative estimates reveal up to 5-fold enrichment of Pt at nanoligament surfaces, compared to the precursor content, in NPG-Pt. The interface between the dealloyed layer and the substrate was captured by APT, for the first time. The findings of this investigation add insight into the functionality of NPG-Pt and its prospective catalytic performance.

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