Engineering topics
Yu, Yang
Publications and source records attributed to Yu, Yang.
Combined Plasmonic Au-nanoparticle and Conducting Metal Oxide High-temperature Optical Sensing with LSTO
<span style="color: rgba(0, 0, 0, 0.79); font-family: "Source Sans Pro", source-sans-pro, museo_sans300, museo-sans, Arial, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);">Fiber optic sensor technology offers several advantages for harsh-environment applications. However, the development of optical gas sensing layers that are stable under harsh environmental conditions is an ongoing research challenge. In this work, electronically conducting metal oxide lanthanum-doped strontium titanate (LSTO) films embedded with gold nanoparticles are examined as a sensing layer for application in reducing gas flows at high temperature (600–800 °C). A strong localized surface plasmon resonance (LSPR) based response to hydrogen is demonstrated in the visible region of the spectrum, while a Drude free electron-based response is observed in the near-IR. Characteristics of these responses are studied both on planar glass substrates and on silica fibers. Charge transfer between the oxide film and the gold nanoparticles is explored as a possible mechanism governing the Au LSPR response and is considered in terms of the corresponding properties of the conducting metal oxide-based matrix phase. Principal component analysis is applied to the combined plasmonic and free-carrier based response over a range of temperatures and hydrogen concentrations. It is demonstrated that the combined visible and near-IR response of these films provides improved versatility for multiwavelength interrogation, as well as improved discrimination of important process parameters (concentration and temperature) through application of multivariate analysis techniques.</span>
Antimycobacterial Rufomycin Analogues from Streptomyces atratus Strain MJM3502
Abstract not provided
Understanding three-dimensionally interconnected porous oxide-derived copper electrocatalyst for selective carbon dioxide reduction
In this study, we have investigated a hierarchical CuO-derived inverse opal (CuO-IO) catalyst with high CO selectivity up to 80–90% and minimal H 2 evolution at moderate potentials for CO 2 electroreduction. The three-dimensionally (3D) structured, porous catalyst was composed of small CuO nanoparticles and exhibited a peak CO faradaic efficiency (FE) of 72.5% (±1.8), complete suppression of H 2 formation, and good stability over 24 hours operation at –0.6 V versus the reversible hydrogen electrode (RHE). In situ Raman, X-ray absorption spectroscopy and X-ray diffraction measurements indicated reduction of the catalyst into metallic Cu0 oxidation state with dominant Cu(111) orientation under electrocatalytic conditions. We suggest that rapid depletion of CO 2 and protons at the highly roughened catalyst surface likely increased the local pH during the electrolysis. The combination of C 1 favoring Cu(111) surfaces and reduced local proton/CO 2 availability facilitated selective conversion of CO 2 into CO and reduced H 2 and C 2 products. Our work provides additional understanding of the structure–property relationships of 3D porous electrocatalysts for CO 2 reduction applications by evaluating the crystallographic orientation, oxidation state, and crystallite size of a CO-selective CuO-IO catalyst under realistic working conditions.
Revealing Electronic Signatures of Lattice Oxygen Redox in Lithium Ruthenates and Implications for High-Energy Li-Ion Battery Material Designs
Anion redox in lithium transition-metal oxides such as Li 2 RuO 3 and Li 2 MnO 3 has catalyzed intensive research efforts to find transition-metal oxides with anion redox that may boost the energy density of lithium-ion batteries. The physical origin of the observed anion redox remains debatable, and more direct experimental evidence is needed. In this work, we have shown electronic signatures of oxygen–oxygen coupling, direct evidence central to lattice oxygen redox (O 2- /(O 2 ) n- ), in charged Li 2– $_x$RuO 3 after Ru oxidation (Ru 4+ /Ru 5+ ) upon first electron removal with lithium deintercalation. Experimental Ru L 3 -edge high-energy-resolution fluorescence-detected X-ray absorption spectra (HERFD-XAS), supported by ab initio simulations, revealed that the increased intensity in the high-energy shoulder upon lithium deintercalation resulted from increased O–O coupling, inducing (O–O) σ*-like states with π overlap with Ru d-manifolds, in agreement with O K-edge XAS spectra. Experimental and simulated O K-edge X-ray emission spectra further supported this observation with the broadening of the oxygen nonbonding feature upon charging, also originated from (O–O) σ* states. This lattice oxygen redox of Li 2–x RuO 3 was accompanied by a small amount of O 2 evolution in the first charge from differential electrochemistry mass spectrometry but diminished in the subsequent cycles, in agreement with the more reduced states of Ru in later cycles from Ru L 3 -edge HERFD-XAS. These observations indicated that Ru redox contributed more to discharge capacities after the first cycle. This study has pinpointed the key spectral fingerprints related to lattice oxygen redox from a molecular level and constructed a transferrable framework to rationally interpret the spectroscopic features by combining advanced experiments and theoretical calculations to design materials for Li-ion batteries and electrocatalysis applications.