Solar‐to‐hydrogen conversion based on photocatalytic and photoelectrocatalytic water splitting is considered as a promising technology for sustainable hydrogen production. Developing earth‐abundant ...H2‐production materials with robust activity and stability has become the mainstream in this field. Due to the unique properties and characteristics, transition metal phosphides (TMPs) have been proven to be high performance co‐catalysts to replace some of the classic precious metal materials in photocatalytic water splitting. In this Minireview, we summarize the recent significant progress of TMPs as cocatalysts for water splitting reaction with high activity and stability. Firstly, the characteristic of TMPs is briefly introduced. Then, we mainly discuss the recent research efforts toward their application as photocatalytic co‐catalysts in photocatalytic H2‐production, O2‐evolution and photoelectrochemical water splitting. Finally, the catalytic mechanism, current existing challenges and future working directions for improving the performance of TMPs are proposed.
What's all the phos about? This Minireview concerns recent progress in metal phosphide‐based heterogeneous photocatalysts for water splitting to produce high‐purity hydrogen. Various systems with optimized or enhanced photocatalytic efficiency are introduced through specific examples. The possible catalytic mechanism, recent challenges, and future research directions for optimizing the performance of metal‐phosphide‐based co‐catalysts are discussed.
There has been strong and growing interest in the development of cost-effective and highly active oxygen evolution reaction (OER) electrocatalysts for alternative fuels utilization and conversion ...devices. We report herein that semimetallic Cu3P nanoarrays directly grown on 3D copper foam (CF) substrate can function as effective electrocatalysts for water oxidation. Specifically, the surface oxidation-activated Cu3P only required a relatively low overpotential of 412 mV to achieve a current density of 50 mA cm–2 and displayed a small Tafel slope of 63 mV dec–1 in 0.1 M KOH solution, on account of the collaborative effect of large roughness factor (RF) and semimetallic character. Following that, investigations into the mechanism revealed the formation of a unique active phase during the water oxidation process in which conductive Cu3P was the core covered with a thin copper oxide/hydroxide layer. Moreover, this Cu3P 3D electrode was also applied to the hydrogen evolution reaction (HER) and showed good catalytic performance and stability under the same basic conditions.
The oxidized 1‐palmitoyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphocholine (ox‐PAPC) products in human high‐density lipoproteins (HDLs) were investigated by low‐flow capillary electrophoresis‐mass ...spectrometry (low‐flow CE‐MS). To accelerate the optimization, native PAPC (n‐PAPC) standard was first analyzed by a commercial CE instrument with a photodiode array detector. The optimal separation buffer contained 60% (v/v) acetonitrile, 40% (v/v) methanol, 20 mM ammonium acetate, 0.5% (v/v) formic acid, and 0.1% (v/v) water. The selected separation voltage and capillary temperature were 20 kV and 23°C. The optimal CE separation buffer was then used for the low‐flow CE‐MS analysis. The selected MS conditions contained heated capillary temperature (250°C), capillary voltage (10 V), and injection time (1 s). No sheath gas was used for MS. The linear range for n‐PAPC was 2.5–100.0 µg/mL. The coefficient of determination (R2) was 0.9918. The concentration limit of detection was 1.52 µg/mL, and the concentration limit of quantitation was 4.60 µg/mL. The optimal low‐flow CE‐MS method showed good repeatability and sensitivity. The ox‐PAPC products in human HDLs were determined based on the in vitro ox‐PAPC products of n‐PAPC standard. Twenty‐one ox‐PAPC products have been analyzed in human HDLs. Uremic patients showed significantly higher levels of 15 ox‐PAPC products than healthy subjects.
Context.
Observations of young, low-mass, main-sequence, and zero-age main-sequence stars show evidence of a correlation between lithium abundance and chromospheric activity, albeit with a very large ...scatter. Fast rotation stars (including T Tauri stars, RS CVn, and BY Dra systems) show the Li I doublet at 6707.8 Å in their spectra. The lithium depletion is probably related to the rotation (turbulent diffusion induced by rotation). Because the flare activity of stars increases with decreasing rotation period, a correlation can be expected between lithium abundance and chromospheric activity for active stars.
Aims.
The aim of this paper is to investigate the relation between lithium abundance and the Ca II H and K emission index (R′
HK
=
L
HK
/
L
bol
) for a sample of active stars.
Methods.
Based on the high-resolution spectroscopic observations, we calculated lithium abundance for 14 chromospherically active late-type stars using the comparison of the measured Li I
λ
670.8 nm equivalent width with curve of growth calculations in non-local-thermodynamic-equilibrium conditions. We also searched the correlation between lithium abundance and the Ca II H & K emission index (log R′
HK
) for the 14 chromospherically active late-type stars.
Results.
The study of the relationship between lithium abundance and the Ca II H & K emission index (log R′
HK
) found that the activity of sample stars increases with increasing lithium abundance. Next, the lithium abundance analogs progressively decrease as the rotation periods increase (rotation becomes slow) and the large values of the log R′
HK
along with small values of Rossby numbers for the sample of chromospherically active stars.
Conclusions.
The lithium abundance (log
N
(Li)) versus the chromospheric activity and log
N
(Li) against the rotation period both indicate that the lithium abundance analogs progressively increase as the chromospheric activity index increases and/or the rotation velocity increase (rotation period becomes small) for our sample of active stars. On the other hand, the log R′
HK
against the Rossby number
R
O
shows that there is a clear trend of increasing activity with increasing rotation velocity for these active stars. Considering that the lithium abundance decreases with increasing stellar age in late-type stars, we can deduce that the chromospheric activity and the rotation velocity both decrease with the increase of stellar age for our sample active stars.
Abstract
Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source ...crowding in the Galactic plane. In this paper, we present a sample of 204 spectroscopically confirmed GPQs at ∣
b
∣ < 20°, 191 of which are new discoveries. This GPQ sample covers a wide redshift range from 0.069 to 4.487. For the subset of 230 observed GPQ candidates, the lower limit of the purity of quasars is 85.2%, and the lower limit of the fraction of stellar contaminants is 6.1%. Using a multicomponent spectral fitting, we measure the emission line and continuum flux of the GPQs, and estimate their single-epoch virial black hole masses. Due to selection effects raised from Galactic extinction and target magnitude, these GPQs have higher black hole masses and continuum luminosities in comparison to the SDSS DR7 quasar sample. The spectral-fitting results and black hole mass estimates are compiled into a main spectral catalog, and an extended spectral catalog of GPQs. The successful identifications prove the reliability of both our GPQ selection methods and the GPQ candidate catalog, shedding light on the astrometric and astrophysical programs that make use of a large sample of GPQs in the future.
ABSTRACT Recently, 1H 0323+342 has attracted a lot of attention as one of several narrow-line Seyfert 1 galaxies detected in the γ-ray band. To understand their central energy engines and jet ...phenomena, the black hole mass is important. We made use of the Lijiang 2.4 m Telescope to monitor 1H 0323+342 for more than two months. This galaxy is one of the candidates for a monitoring project of super-Eddington accreting massive black holes. The reverberation mapping shows that Hβ emission has a delayed response of days with respect to the SDSS g′ light curve in the rest frame. The optical Fe ii variations were detected after subtracting host contaminations, and a reverberation with a delay of days was found in the rest frame. By assuming the viral factor fBLR = 6.17 for the broad-line region (BLR) velocity characterized by FWHM because of the face-on orientation, we find that the black hole mass derived from Hβ is , and the accretion rate is , where , is the mass accretion rate, LEdd is the Eddington luminosity, and c is the speed of light. This black hole is one order less massive than that given by the Magorrian relation from the bulge mass. We test the relation between accretion rates and radio-loudnesses in all mapped radio-loud active galactic nuclei, and find that 1H 0323+342 falls within this group.
We developed a spectroscopic monitoring project to investigate the kinematics of the broad-line region (BLR) in active galactic nuclei (AGNs) with ultrafast outflows (UFOs). Mrk 79 is a radio-quiet ...AGN with UFOs and warm absorbers and has been monitored by three reverberation mapping (RM) campaigns, but its BLR kinematics are not yet understood. In this paper, we report the results from a new RM campaign of Mrk 79, which was undertaken with the Lijiang 2.4 m telescope. Mrk 79 appears to come out the faint state, with the mean flux approximately a magnitude fainter than the historical record. We successfully measured the lags of the broad emission lines including Hβ λ4861, Hγ λ4340, He ii λ4686, and He i λ5876 with respect to the varying AGN continuum. Based on the broad Hβ λ4861 line, we measured a black hole mass of M = 5.13 − 1.55 + 1.57 × 10 7 M , and an estimated accretion rate of M ̇ = ( 0.05 0.02 ) L Edd c − 2 , indicating that Mrk 79 is a sub-Eddington accretor. We found that Mrk 79 deviates from the canonical Radius−Luminosity relationship. The marginal blueshift of the broad He ii λ4686 line detected from the rms spectrum indicates outflow of high-ionization gas. The velocity-resolved lag profiles of the broad Hγ λ4340, Hβ λ4861, and He i λ5876 lines show similar signatures such that the largest lag occurs in the red wing of the lines and then the lag decreases to both sides. These signatures may suggest that the BLR of Keplerian motion probably exists as outflow gas motion. All findings including UFOs, warm absorbers, and the kinematics of high- and low-ionization BLR, may provide indirect evidence that the BLR of Mrk 79 probably originates from a disk wind.
Two mononuclear ruthenium complexes Ru(H2tcbp)(isoq)2 (1) and Ru(H2tcbp)(pic)2 (2) (H4tcbp=4,4′,6,6′‐tetracarboxy‐2,2′‐bipyridine, isoq=isoquinoline, pic=4‐picoline) are synthesized and fully ...characterized. Two spare carboxyl groups on the 4,4′‐positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium‐tin‐oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10 h of electrolysis under 1.42 V vs. NHE, corresponding to a turnover frequency of 0.41 s−1. The low overpotential (0.17 V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using Ru(bpy)32+ (P1) (bpy=2,2′‐bipyridine) or Ru(bpy)2(4,4′‐(COOEt)2‐bpy)2+ (P2) as a photosensitizer. In a three‐component system containing 1 or 2 as a light‐driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or CoCl(NH3)5Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81 s−1 and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85 μA cm−2 is obtained by applying 0.3 V bias vs. NHE.
WOC immobilized on a semiconductor: Two mononuclear RuII complexes with free carboxyl groups (water‐oxidation catalyst, WOC) can anchor covalently to a semiconductor. The electrochemical, photochemical, and photoelectrochemical water oxidation performance of the assembly devices in neutral aqueous solution is investigated (see figure).
ABSTRACT Extensive and independent observations of Type Ia supernova (SN Ia) SN 2013dy are presented, including a larger set of UBVRI photometry and optical spectra from a few days before the peak ...brightness to ∼ 200 days after explosion, and ultraviolet (UV) photometry spanning from t -10 days to t +15 days refers to the B band maximum. The peak brightness (i.e., MB = -19.65 0.40 mag; Lmax = 1.95 0.55 × 1043 erg s−1) and the mass of synthesized 56Ni (i.e., M(56Ni) = 0.90 0.26 M ) are calculated, and they conform to the expectation for an SN Ia with a slow decline rate (i.e., Δm15(B) = 0.90 0.03 mag). However, the near infrared (NIR) brightness of this SN (i.e., MH = -17.33 0.30 mag) is at least 1.0 mag fainter than usual. Besides, spectroscopy classification reveals that SN 2013dy resides on the border of "core normal" and "shallow silicon" subclasses in the Branch et al. classification scheme, or on the border of the "normal velocity" SNe Ia and 91T/99aa-like events in the Wang et al. system. These suggest that SN 2013dy is a slow-declining SN Ia located on the transitional region of nominal spectroscopic subclasses and might not be a typical normal sample of SNe Ia.
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