Additional file 1: of Enhancement of Photo-Oxidation Activities Depending on Structural Distortion of Fe-Doped TiO2 Nanoparticles

Supplementary material. Digital images and SEM images of Fe@TiO2 nanoparticles, XRD, and Raman intensity plot. Figure S1. Digital images of the Fe@TiO2 dispersed solution with several of Fe dopant concentration. Figure S2. SEM images as the morphologies varying the doping level of Fe: (a) 1 wt %, (b) 3 wt %, (c) 5 wt %; and their high-resolution images (a′), (b′), and (c′), respectively. Figure S3. EDX spectra with Fe peak (marked by black arrows) of big particles: (a) 1 wt% Fe@TiO2, (b) 3 wt% Fe@TiO2, and (c) 5 wt% Fe@TiO2. Figure S4. (a) XRD peak position and correspond lattice constant of (101) plane of anatase TiO2 structure and (b) Raman intensity ratio of I410 (α-Fe2O3 Eg) to I144 (anatase TiO2 Eg). Figure S5. Spectral subtraction of valence band spectra by bare TiO2 peak: (a) 1 wt% Fe@TiO2, (b) 3 wt% Fe@TiO2, and (c) 5 wt% Fe@TiO2

Nitrogen-Deficient ORR Active Sites Formation by Iron-Assisted Water Vapor Activation of Electrospun Carbon Nanofibers

Fe- and N-modified carbon nanofibers (Fe–CNF) were synthesized via electrospinning and pyrolysis as electrocatalysts for oxygen reduction reaction (ORR). In order to increase the exposed surface area with the active sites buried inside Fe–CNF, we attempted water vapor activation for Fe–CNF and observed a substantial improvement of ORR activity up to the comparable level with Pt/C. Unlike what was expected, however, water vapor activation did not significantly increase the specific surface area of Fe–CNF; instead, it induced a depletion of surface N content, which makes it difficult to explain the improved ORR activity with the increase of surface area with N-based active sites. In water vapor activation, the chemical phase of embedded particles is changed from Fe₃C to Fe₃O₄ and nitrogen-free Fe- and C-based ORR active sites were exposed, which seemed to be related with hierarchical macro/mesopore structure and graphitic edge defects. This study demonstrates a facile activation method for better ORR activity of Fe-modified CNF and suggests a potential relationship of surface carbon structure with the catalytic activity toward ORR rather than the type and concentration of N in Fe–CNF, which should be investigated further

Efficient CO Oxidation by 50-Facet Cu₂O Nanocrystals Coated with CuO Nanoparticles

As carbon monoxide oxidation is widely used for various chemical processes (such as methanol synthesis and water-gas shift reactions H₂O + CO ⇄ CO₂ + H₂) as well as in industry, it is essential to develop highly energy efficient, inexpensive, and eco-friendly catalysts for CO oxidation. Here we report green synthesis of ∼10 nm sized CuO nanoparticles (NPs) aggregated on ∼400 nm sized 50-facet Cu₂O polyhedral nanocrystals. This CuO-NPs/50-facet Cu₂O shows remarkable CO oxidation reactivity with very high specific CO oxidation activity (4.5 μmol_CO m^–2 s^–1 at 130 °C) and near-complete 99.5% CO conversion efficiency at ∼175 °C. This outstanding catalytic performance by CuO NPs over the pristine multifaceted Cu₂O nanocrystals is attributed to the surface oxygen defects present in CuO NPs which facilitate binding of CO and O₂ on their surfaces. This new material opens up new possibilities of replacing the usage of expensive CO oxidation materials

Long-Range Lattice Engineering of MoTe₂ by a 2D Electride

Doping two-dimensional (2D) semiconductors beyond their degenerate levels provides the opportunity to investigate extreme carrier density-driven superconductivity and phase transition in 2D systems. Chemical functionalization and the ionic gating have achieved the high doping density, but their effective ranges have been limited to ∼1 nm, which restricts the use of highly doped 2D semiconductors. Here, we report on electron diffusion from the 2D electride [Ca₂N]⁺·e^– to MoTe₂ over a distance of 100 nm from the contact interface, generating an electron doping density higher than 1.6 × 10¹⁴ cm^–2 and a lattice symmetry change of MoTe₂ as a consequence of the extreme doping. The long-range lattice symmetry change, suggesting a length scale surpassing the depletion width of conventional metal–semiconductor junctions, was a consequence of the low work function (2.6 eV) with highly mobile anionic electron layers of [Ca₂N]⁺·e^–. The combination of 2D electrides and layered materials yields a novel material design in terms of doping and lattice engineering