Cu metal embedded in oxidized matrix catalyst to promote CO_2 activation and CO dimerization for electrochemical reduction of CO_2

We propose and validate with quantum mechanics methods a unique catalyst for electrochemical reduction of CO_2 (CO_2RR) in which selectivity and activity of CO and C_2 products are both enhanced at the borders of oxidized and metallic surface regions. This Cu metal embedded in oxidized matrix (MEOM) catalyst is consistent with observations that Cu_2O-based electrodes improve performance. However, we show that a fully oxidized matrix (FOM) model would not explain the experimentally observed performance boost, and we show that the FOM is not stable under CO_2 reduction conditions. This electrostatic tension between the Cu^+ and Cu^0 surface sites responsible for the MEOM mechanism suggests a unique strategy for designing more efficient and selective electrocatalysts for CO_2RR to valuable chemicals (HCOx), a critical need for practical environmental and energy applications

Hydrological and biogeochemical controls on absorption and fluorescence of dissolved organic matter in the northern South China Sea

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 122 (2017): 3405–3418, doi:10.1002/2017JG004100.The Kuroshio intrusion from the West Philippine Sea (WPS) and mesoscale eddies are important hydrological features in the northern South China Sea (SCS). In this study, absorption and fluorescence of dissolved organic matter (CDOM and FDOM) were determined to assess the impact of these hydrological features on DOM dynamics in the SCS. DOM in the upper 100 m of the northern SCS had higher absorption, fluorescence, and degree of humification than in the Kuroshio Current of the WPS. The results of an isopycnal mixing model showed that CDOM and humic-like FDOM inventories in the upper 100 m of the SCS were modulated by the Kuroshio intrusion. However, protein-like FDOM was influenced by in situ processes. This basic trend was modified by mesoscale eddies, three of which were encountered during the fieldwork (one warm eddy and two cold eddies). DOM optical properties inside the warm eddy resembled those of DOM in the WPS, indicating that warm eddies could derive from the Kuroshio Current through Luzon Strait. DOM at the center of cold eddies was enriched in humic-like fluorescence and had lower spectral slopes than in eddy-free waters, suggesting inputs of humic-rich DOM from upwelling and enhanced productivity inside the eddy. Excess CDOM and FDOM in northern SCS intermediate water led to export to the Pacific Ocean interior, potentially delivering refractory carbon to the deep ocean. This study demonstrated that DOM optical properties are promising tools to study active marginal sea-open ocean interactions.National Natural Science Foundation of China Grant Numbers: U1305231, 412760642018-06-2

Cobalt doped black TiO_2 nanotube array as a stable anode for oxygen evolution and electrochemical wastewater treatment

TiO_2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO_2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped black-TiO_2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm^(-2). Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (O_v) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, Ov, and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO_2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoO_x film on top of Co-Black electrode. The CoO_x/Co-Black composite electrode was found to have a lower OER overpotential (352 mV) compared to a DSA IrO_2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm^(-2)

Strategizing the IT Entrepreneurial Teams: A Dynamic Equilibrium Perspective

We conducted a multiple case study on six IT entrepreneurial firms to examine and compare their differences. Results show that as they evolve from emergence stage to early growth stage, they encounter misalignments between venture strategies and entrepreneurial teams’ social capital configurations, prompting adjustments to achieve dynamic equilibriums. Differentiating between IT product and IT service entrepreneurial firms, we found that IT product entrepreneurial firms switch their team management strategy from Interests Alignment to a combination of Diversifying Expansion, Functional Specialization, Cognition Unification and Competition Promotion when their venture strategy changes from product R&D at emergence stage to market expansion at the early growth stage. Conversely, IT service entrepreneurial firms switch from the combination of Diversifying Expansion, Cognition Unification and Competition Promotion to Interests Alignment when their venture strategy evolves from market expansion at emergence stage to service R&D at the early growth stage. Important theoretical and practical implications are drawn

Preparation of an Amidated Graphene Oxide/Sulfonated Poly Ether Ether Ketone (AGO/SPEEK) Modified Atmosphere Packaging for the Storage of Cherry Tomatoes

The shelf life of cherry tomatoes is short so that new and efficient preservation techniques or procedures are required to reduce postharvest losses. This study focused on the development of a sulfonated poly ether ether ketone (SPEEK) film incorporated with amidated graphene oxide (AGO), for the storage of cherry tomatoes in modified atmosphere packaging. The mechanical properties, gas permeability, and moisture permeability were subsequently tested. The evolution of attributes related to shelf life, such as gas composition, physicochemical properties, and sensory properties were also monitored during storage trials. AGO, as an inorganic filler, increases the thermal stability and mechanical properties of SPEEK-based films, while it reduces the water absorption, swelling rate, and moisture permeability. Importantly, all the AGO/SPEEK films exhibited enhanced gas permeability and selective permeability of CO2/O2 relative to the SPEEK film. Moreover, 0.9% (w/w) AGO/SPEEK film showed an enhanced permeability coefficient of CO2, corresponding to an increase of 50.7%. It could further improve the selective coefficient of CO2/O2 to 67.1%. The results of preservation at 8 °C revealed that: 0.9% (w/w) AGO/SPEEK film was significantly effective at maintaining the quality and extending the shelf life of cherry tomatoes from 15 to 30 days, thereby suggesting the potential for applying AGO-incorporated SPEEK films for food packaging materials

The complete chloroplast genome of Epimedium xichangense Y. J. Zhang (Berberidaceae)

Epimedium xichangense, a critically endangered herb with limited population, mainly distributes in Sichuan province, China. In our study, we obtained the complete chloroplast genome of E. xichangense with a length of 158,955 bp, including a large single copy region of 86,478 bp, small single copy region of 17,027 bp, and a pair of inverted repeat regions of 27,725 bp. The GC content in the whole chloroplast genome of E. xichangense is 38.81%. Among the 112 unique genes in the circular genome, 30 tRNA, four rRNA and 78 protein-coding genes were successfully annotated. We constructed the Maximum likelihood (ML) tree with 26 species, and came to the conclusion that E. xichangense was phylogenetically closely related to E. acuminatum and E. chlorandrum

Multifunctional Active-Center-Transferable Platinum/Lithium Cobalt Oxide Heterostructured Electrocatalysts towards Superior Water Splitting

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Designing cost-effective and efficient electrocatalysts plays a pivotal role in advancing the development of electrochemical water splitting for hydrogen generation. Herein, multifunctional active-center-transferable heterostructured electrocatalysts, platinum/lithium cobalt oxide (Pt/LiCoO2) composites with Pt nanoparticles (Pt NPs) anchored on LiCoO2 nanosheets, are designed towards highly efficient water splitting. In this electrocatalyst system, the active center can be alternatively switched between Pt species and LiCoO2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Specifically, Pt species are the active centers and LiCoO2 acts as the co-catalyst for HER, whereas the active center transfers to LiCoO2 and Pt turns into the co-catalyst for OER. The unique architecture of Pt/LiCoO2 heterostructure provides abundant interfaces with favorable electronic structure and coordination environment towards optimal adsorption behavior of reaction intermediates. The 30 % Pt/LiCoO2 heterostructured electrocatalyst delivers low overpotentials of 61 and 285 mV to achieve 10 mA cm−2 for HER and OER in alkaline medium, respectively