The use of nitrogen fertilizers has been estimated to have supported 27% of the world’s population over the past century. Urea (CO(NH2)2) is conventionally synthesized through two consecutive ...industrial processes, N2 + H2 → NH3 followed by NH3 + CO2 → urea. Both reactions operate under harsh conditions and consume more than 2% of the world’s energy. Urea synthesis consumes approximately 80% of the NH3 produced globally. Here we directly coupled N2 and CO2 in H2O to produce urea under ambient conditions. The process was carried out using an electrocatalyst consisting of PdCu alloy nanoparticles on TiO2 nanosheets. This coupling reaction occurs through the formation of C–N bonds via the thermodynamically spontaneous reaction between *N=N* and CO. Products were identified and quantified using isotope labelling and the mechanism investigated using isotope-labelled operando synchrotron-radiation Fourier transform infrared spectroscopy. A high rate of urea formation of 3.36 mmol g–1 h–1 and corresponding Faradic efficiency of 8.92% were measured at –0.4 V versus reversible hydrogen electrode.Conventionally, urea is synthesized via two consecutive processes, N2 + H2 → NH3 followed by NH3 + CO2. Now, an electrocatalyst consisting of PdCu alloy nanoparticles on TiO2 nanosheets has been shown to directly couple N2 and CO2 in H2O to produce urea under ambient conditions.
Chemical manifestations of strong light-matter coupling have recently been a subject of intense experimental and theoretical studies. Here we review the present status of this field. Section 1 is an ...introduction to molecular polaritonics and to collective response aspects of light-matter interactions. Section 2 provides an overview of the key experimental observations of these effects, while Section 3 describes our current theoretical understanding of the effect of strong light-matter coupling on chemical dynamics. A brief outline of applications to energy conversion processes is given in Section 4. Pending technical issues in the construction of theoretical approaches are briefly described in Section 5. Finally, the summary in Section 6 outlines the paths ahead in this exciting endeavor.
We summarize and reanalyze observations bearing on missing galactic baryons, where we propose a consistent picture for halo gas in L L* galaxies. The hot X-ray-emitting halos are detected to 50-70 ...kpc, where typically Mhot(<50 kpc) ∼ 5 × 109 M , and with density n ∝ r−3/2. When extrapolated to R200, the gas mass is comparable to the stellar mass, but about half of the baryons are still missing from the hot phase. If extrapolated to 1.7R200-3R200, the ratio of baryon to dark matter approaches the cosmic value. Significantly flatter density profiles are unlikely for R < 50 kpc, and they are disfavored but not ruled out for R > 50 kpc. For the Milky Way, the hot halo metallicity lies in the range 0.3-1 solar for R < 50 kpc. Planck measurements of the thermal Sunyaev-Zel'dovich (SZ) effect toward stacked luminous galaxies (primarily early type) indicate that most of their baryons are hot, are near the virial temperature, and extend beyond R200. This stacked SZ signal is nearly an order of magnitude larger than that inferred from the X-ray observations of individual (mostly spiral) galaxies with M* > 1011.3 M . This difference suggests that the hot halo properties are distinct for early- and late-type galaxies, possibly due to different evolutionary histories. For the cooler gas detected in UV absorption line studies, we argue that there are two absorption populations: extended halos, and disks extending to ∼50 kpc, containing most of this gas, and with masses a few times lower than the stellar masses. Such extended disks are also seen in 21 cm H i observations and in simulations.
The nitrogenous nucleophile electrooxidation reaction (NOR) plays a vital role in the degradation and transformation of available nitrogen. Focusing on the NOR mediated by the β‐Ni(OH)2 electrode, we ...decipher the transformation mechanism of the nitrogenous nucleophile. For the two‐step NOR, proton‐coupled electron transfer (PCET) is the bridge between electrocatalytic dehydrogenation from β‐Ni(OH)2 to β‐Ni(OH)O, and the spontaneous nucleophile dehydrogenative oxidation reaction. This theory can give a good explanation for hydrazine and primary amine oxidation reactions, but is insufficient for the urea oxidation reaction (UOR). Through operando tracing of bond rupture and formation processes during the UOR, as well as theoretical calculations, we propose a possible UOR mechanism whereby intramolecular coupling of the N−N bond, accompanied by PCET, hydration and rearrangement processes, results in high performance and ca. 100 % N2 selectivity. These discoveries clarify the evolution of nitrogenous molecules during the NOR, and they elucidate fundamental aspects of electrocatalysis involving nitrogen‐containing species.
During urea electrooxidation over a Ni(OH)2 electrode the dehydrogenation reaction from β‐Ni(OH)2 to β‐Ni(OH)O can lead to spontaneous urea dehydrogenation. Spontaneous intramolecular coupling of the N−N bond and hydration of urea dehydrogenation intermediates play important roles in the oxidation path from urea to N2 and CO2.
Recent fruitful studies on rechargeable zinc-air battery have led to emergence of various bifunctional oxygen electrocatalysts, especially metal-based materials. However, their electrocatalytic ...configuration and evolution pathway during battery operation are rarely spotlighted. Herein, to depict the underlying behaviors, a concept named dynamic electrocatalyst is proposed. By selecting a bimetal nitride as representation, a current-driven "shell-bulk" configuration is visualized via time-resolved X-ray and electron spectroscopy analyses. A dynamic picture sketching the generation and maturation of nanoscale oxyhydroxide shell is presented, and periodic valence swings of performance-dominant element are observed. Upon maturation, zinc-air battery experiences a near two-fold enlargement in power density to 234 mW cm
, a gradual narrowing of voltage gap to 0.85 V at 30 mA cm
, followed by stable cycling for hundreds of hours. The revealed configuration can serve as the basis to construct future blueprints for metal-based electrocatalysts, and push zinc-air battery toward practical application.
Molecular electronic devices with tunable conductance states show great potential in building memories and logic components for next-generation circuits. In recent years, photoswitchable molecular ...devices have attracted worldwide interest because of the high spatial and temporal resolution, low cost and non-invasibility of light. Herein, an overview of the progress in photoswitching molecular junctions based on single molecules or self-assembled monolayers of photochromic molecules (
i.e.
, azobenzene, diarylethene, dihydroazulene, spiropyran and dihydropyrene) in the recent decade and a brief description of methods to construct photoswitchable molecular devices are provided. An outlook of the future research directions and challenges for this field is also presented.
Recent advances in photoswitchable molecular devices based on single molecules or self-assembled monolayers of photochromic molecules are summarized and discussed.
Abstract
Interferon-gamma (IFN-γ) is a cytokine involved in the pathogenesis of Takayasu’s arteritis (TAK). However, the source of IFN-γ in TAK patients is not fully clear. We aimed to investigate ...the source of IFN-γ in TAK. 60 TAK patients and 35 health controls were enrolled. The lymphocyte subsets of peripheral blood were detected by flow cytometry, cytokines were detected by Bio-plex. The correlation among lymphocyte subsets, cytokines and disease activity indexes was analyzed by person correlation. The level of serum IFN-γ in TAK patients was significantly increased (
P
< 0.05). The percentage of CD3
+
IFN-γ
+
cells in peripheral blood CD3
+
cells was significantly higher in TAK patients than that of healthy control group (
P
= 0.002). A higher proportion of CD3
+
CD8
+
IFN-γ
+
cells/CD3
+
IFN-γ
+
cells (40.23 ± 11.98% vs 35.12 ± 11.51%,
P
= 0.049), and a significantly lower CD3
+
CD4
+
IFN-γ
+
/ CD3
+
CD8
+
IFN-γ
+
ratio (1.34 ± 0.62% vs 1.80 ± 1.33%,
P
= 0.027) were showed in the TAK group than that of control group. The CD3
+
CD8
+
IFN-γ
+
/CD3
+
IFN-γ
+
ratio was positively correlated with CD3
+
IFN-γ
+
cells/ CD3
+
cells ratio (r = 0.430,
P
= 0.001), serum IFN-γ level (r = 0.318,
P
= 0.040) and IL-17 level (r = 0.326,
P
= 0.031). It was negatively correlated with CD3
+
CD4
+
IFN-γ
+
/CD3
+
IFN-γ
+
ratio (r = − 0.845,
P
< 0.001). IFN-γ secreted by CD3
+
CD8
+
T cells is an important source of serum IFN-γ in TAK patients.
High‐entropy oxides (HEOs), a new concept of entropy stabilization, exhibit unique structures and fascinating properties, and are thus important class of materials with significant technological ...potential. However, the conventional high‐temperature synthesis techniques tend to afford micron‐scale HEOs with low surface area, and the catalytic activity of available HEOs is still far from satisfactory because of their limited exposed active sites and poor intrinsic activity. Here we report a low‐temperature plasma strategy for preparing defect‐rich HEOs nanosheets with high surface area, and for the first time employ them for 5‐hydroxymethylfurfural (HMF) electrooxidation. Owing to the nanosheets structure, abundant oxygen vacancies, and high surface area, the quinary (FeCrCoNiCu)3O4 nanosheets deliver improved activity for HMF oxidation with lower onset potential and faster kinetics, outperforming that of HEOs prepared by high‐temperature method. Our method opens new opportunities for synthesizing nanostructured HEOs with great potential applications.
Defect‐rich high‐entropy oxides (HEOs) nanosheets with high surface area are synthesized through a plasma strategy under low‐temperature. The unique structural and compositional advantages endow the HEOs nanosheets with superior electrocatalytic activity for 5‐hydroxymethylfurfural oxidation.
Electrocatalysis is dominated by reaction at the solid–liquid–gas interface; surface properties of electrocatalysts determine the electrochemical behavior. The surface charge of active sites on ...catalysts modulate adsorption and desorption of intermediates. However, there is no direct evidence to bridge surface charge and catalytic activity of active sites. Defects (active sites) were created on a HOPG (highly oriented pyrolytic graphite) surface that broke the intrinsic sp2‐hybridization of graphite by plasma, inducing localization of surface charge onto defective active sites, as shown by scanning ion conductance microscopy (SICM) and Kelvin probe force microscopy (KPFM). An electrochemical test revealed enhanced intrinsic activity by the localized surface charge. DFT calculations confirmed the relationship between surface charge and catalytic activity. This work correlates surface charge and catalytic activity, providing insights into electrocatalytic behavior and guiding the design of advanced electrocatalysts.
Highly oriented pyrolytic graphite (HOPG) was employed as a model to analyze the promotion of surface charge for electrocatalytic reactions. Via plasma irradiation, numerous defects are generated, which would induce charge re‐distribution on the surface of HOPG. A direct relationship between surface charge and the electrocatalytic activity is proposed.
This paper formulates the price-based unit commitment (PBUC) problem based on the mixed integer programming (MIP) method. The proposed PBUC solution is for a generating company (GENCO) with thermal, ...combined-cycle, cascaded-hydro, and pumped-storage units. The PBUC solution by utilizing MIP is compared with that of Lagrangian relaxation (LR) method. Test results on the modified IEEE 118-bus system show the efficiency of our MIP formulation and advantages of the MIP method for solving PBUC. It is also shown that MIP could be applied to solve hydro-subproblems including cascaded-hydro and pumped-storage units in the LR-based framework of hydro-thermal coordination. Numerical experiments on large systems show that the MIP-based computation time and memory requirement would represent the major obstacles for applying MIP to large UC problems. It is noted that the solution of large UC problems could be accomplished by improving the MIP formulation, the utilization of specific structure of UC problems, and the use of parallel processing.
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