Free‐standing 3D metal nanostructures represent an upcoming class of electrocatalysts for fuel cell technology, combining high aging stability and activity with efficient metal utilization while abstaining from additives such as polymer binders. Until now, most fabrication routes are complex and produce disordered nanostructures. Here, we present a highly adjustable, wet‐chemical synthesis route toward ordered, thin‐walled Pt nanotube networks. The approach includes an optimized electroless plating procedure and enables easy regulation of structural parameters (i. e. nanotube diameter, wall thickness, density) by using ion track‐etched polycarbonate templates. In comparison to individual nanotubes, the resulting nanonetworks exhibit a free‐standing and robust frame, which is a great advantage for use in various electrochemical and catalytic applications. Cyclic voltammetry studies of the methanol oxidation reaction demonstrate enhanced electrocatalytic activity compared to commercially available Pt nanoparticles. The nanonetworks provide outstanding long‐life stability with up to 97 % of the initial active surface area after 1000 cycles, which makes them a promising material in different application fields, for example, in direct methanol fuel cells.

Owing to their large surface area, continuous conduction paths, high activity, and pronounced anisotropy, nanowires are pivotal for a wide range of applications, yet far from thermodynamic equilibrium. Their susceptibility toward degradation necessitates an in-depth understanding of the underlying failure mechanisms to ensure reliable performance under operating conditions. In this study, we present an in-depth analysis of the thermally triggered Plateau–Rayleigh-like morphological instabilities of electrodeposited, polycrystalline, 20–40 nm thin platinum nanowires using in situ transmission electron microscopy in a controlled temperature regime, ranging from 25 to 1100 °C. Nanowire disintegration is heavily governed by defects, while the initially present, frequent but small thickness variations do not play an important role and are overridden later during reshaping. Changes of the exterior wire morphology are preceded by shifts in the internal nanostructure, including grain boundary straightening, grain growth, and the formation of faceted voids. Surprisingly, the nanowires segregate into two domain types, one being single-crystalline and essentially void-free, while the other preserves void-pinned grain boundaries. While the single-crystalline domains exhibit fast Pt transport, the void-containing domains are unexpectedly stable, accumulate platinum by surface diffusion, and act as nuclei for the subsequent nanowire splitting. This study highlights the vital role of defects in Plateau–Rayleigh-like thermal transformations, whose evolution not only accompanies but guides the wire reshaping. Thus, defects represent strong parameters for controlling the nanowire decay and must be considered for devising accurate models and simulations.

Mass spectrometric comparison of swift heavy ion-induced and anaerobic thermal degradation of polymers, Radiation Physics and Chemistry,

Understanding the electrical and thermal transport properties of polycrystalline metallic nanostructures is of great interest for applications in microelectronics. In view of the diverse experimental results in polycrystalline metallic nanowires and nanofilms, it is a long-standing question whether their electrical and thermal properties can be well predicted by a practical model. By eliminating the effects of electrical and thermal contact resistances, we measure the electrical and thermal conductivities of three different polycrystalline Pt nanowires. The electron scattering at the surface is found to be diffusive, and the charge reflection coefficient at grain boundaries is proved to be a function of the melting point. The Lorenz number is observed to be suppressed from the free-electron value by about 30%, which can be explained by introducing a thermal reflection coefficient in calculating the thermal conductivity to account for the small angle scattering effect involving phonons at the grain boundaries. Using this model, both the electrical and thermal conductivities of the polycrystalline Pt nanowires are calculated at different diameters and temperatures.

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