Nanoscale elastic strain mapping of polycrystalline materials

<p>Measuring elastic strain with nanoscale resolution has historically been very difficult and required a marriage of simulations and experiments. Nano precession electron diffraction provides excellent strain and spatial resolution but has traditionally only been applied to single-crystalline semiconductors. The present study illustrates that the technique can also be applied to polycrystalline materials. The strain resolution was determined to be 0.15% and 0.10% for polycrystalline copper and boron carbide, respectively. Local strain maps were obtained near grain boundaries in boron carbide and dislocations in magnesium and shown to correlate with expected values, thus demonstrating the efficacy of this technique.</p> <p>This study demonstrates that nano precession electron diffraction can be extended from semiconductor devices to polycrystalline metals and ceramics to map nanoscale elastic strain fields with high strain resolution.</p

Mechanistic Insights for Low-Overpotential Electroreduction of CO₂ to CO on Copper Nanowires

Recent developments of copper (Cu)-based nanomaterials have enabled the electroreduction of CO₂ at low overpotentials. The mechanism of low-overpotential CO₂ reduction on these nanocatalysts, however, largely remains elusive. We report here a systematic investigation of CO₂ reduction on highly dense Cu nanowires, with the focus placed on understanding the surface structure effects on the formation of *CO (* denotes an adsorption site on the catalyst surface) and the evolution of gas-phase CO product (CO­(g)) at low overpotentials (more positive than −0.5 V). Cu nanowires of distinct nanocrystalline and surface structures are studied comparatively to build up the structure–property relationships, which are further interpreted by performing density functional theory (DFT) calculations of the reaction pathway on the various facets of Cu. A kinetic model reveals competition between CO­(g) evolution and *CO poisoning depending on the electrode potential and surface structures. Open and metastable facets such as (110) and reconstructed (110) are found to be likely the active sites for the electroreduction of CO₂ to CO at the low overpotentials

Low-Overpotential Electroreduction of Carbon Monoxide Using Copper Nanowires

We report on Cu nanowires as highly active and selective catalysts for electroreduction of CO at low overpotentials. The Cu nanowires were synthesized by reducing pregrown CuO nanowires, with the surface structures tailored by tuning the reduction conditions for improved catalytic performance. The optimized Cu nanowires achieved 65% faradaic efficiency (FE) for CO reduction and 50% FE toward production of ethanol at potentials more positive than −0.5 V (versus reversible hydrogen electrode, RHE). Structural analyses and computational simulations suggest that the CO reduction activity may be associated with the coordinately unsaturated (110) surface sites on the Cu nanowires