The generation of hydrogen from water using sunlight could potentially form the basis of a clean and renewable source of energy. Various water-splitting methods have been investigated previously, but the use of photocatalysts to split water into stoichiometric amounts of H2 and O2 (overall water splitting) without the use of external bias or sacrificial reagents is of particular interest because of its simplicity and potential low cost of operation. However, despite progress in the past decade, semiconductor water-splitting photocatalysts (such as (Ga1-xZnx)(N1-xOx)) do not exhibit good activity beyond 440 nm (refs 1,2,9) and water-splitting devices that can harvest visible light typically have a low solar-to-hydrogen efficiency of around 0.1%. Here we show that cobalt(II) oxide (CoO) nanoparticles can carry out overall water splitting with a solar-to-hydrogen efficiency of around 5%. The photocatalysts were synthesized from non-active CoO micropowders using two distinct methods (femtosecond laser ablation and mechanical ball milling), and the CoO nanoparticles that result can decompose pure water under visible-light irradiation without any co-catalysts or sacrificial reagents. Using electrochemical impedance spectroscopy, we show that the high photocatalytic activity of the nanoparticles arises from a significant shift in the position of the band edge of the material.
Batteries with lithium metal anodes
are promising because of lithium’s
high energy density. However, the growth of Li dendrites on the surface
of the Li electrode in a liquid electrolyte during cycling reduces
the safety and cycle performance of batteries, hindering their commercial
application. In this work, we observe for the first time a smooth
and dendrite-free Li deposition with a vertically grown, self-aligned,
and highly compact columnar structure formed during cycling in a mixed
carbonate–ether electrolyte. The stable microsized (∼10
μm in diameter and ∼20 μm in length) Li deposits
are aligned in arrays on the surface of the Li electrode. The columnar
Li deposits still exhibit a dendrite-free morphology and a compact
structure after 200 cycles at a current density of 1 mA/cm2 and a 1.5 mAh/cm2 cycling capacity in a mixed carbonate–ether
electrolyte. This work shows an optimiztic outlook for Li batteries
with liquid electrolytes.
Lithium complexes containing bidentate dianionic trityl/aryloxide ligands, Li2[ROC](Et2O)n ([ROC]2– = [κ2‐O,C‐OC6H2‐2‐C(3,5‐R2C6H3)2‐4,6‐tBu2]2–; 2a (R = H, n = 1) and 2b (R = Me, n = 0)) were synthesized through double metalation of ortho‐benzhydryl phenols with nBuLi. Similarly, sodium compound Na2[HOC](THF)2.5 (3a) was obtained when phenol H2[HOC] (1a) was treated with two equiv. of nBuLi/NaOtBu. The lithium compounds were employed for the preparation of other metal complexes supported by [ROC]2– ligands, i.e. {Zn[ROC](THF)}2 (R = H (4a) or Me (4b)), Sn[HOC]2 (5a) and Cp*Ir[MeOC] (6b, Cp* = η5‐C5Me5), by salt metathesis reactions with metal halides. The solid‐state structures of all metal complexes were established by X‐ray crystallography. The nuclearity of these metal complexes and the coordination fashion of the [ROC]2– ligands were found to be highly dependent on the identity of metal centers. Additionally, compound 2a was found to be facilely oxidized, as revealed by both electrochemical and reactivity study.
The search of novel quasi‐1D materials is one of the important aspects in the field of material science. Toroidal moment, the order parameter of ferrotoroidic order, can be generated by a head‐to‐tail configuration of magnetic moment. It has been theoretically proposed that 1D dimerized and antiferromagnetic (AFM)‐like spin chain hosts ferrotoroidicity and has the toroidal moment composed of only two antiparallel spins. Here, the authors report a ferrotoroidic candidate of Ba6Cr2S10 with such a theoretical model of spin chain. The structure consists of unique dimerized face‐sharing CrS6 octahedral chains along the c axis. An AFM‐like ordering at ≈10 K breaks both space‐ and time‐reversal symmetries and the magnetic point group of mm′2′allows three ferroic orders in Ba6Cr2S10: (anti)ferromagnetic, ferroelectric, and ferrotoroidic orders. Their investigation reveals that Ba6Cr2S10 is a rare ferrotoroid ic candidate with quasi 1D spin chain, which can be considered as a starting point for the further exploration of the physics and applications of ferrotoroidicity.
Distinctive superconducting behaviors between bulk and monolayer FeSe make it challenging to obtain a unified picture of all FeSe-based superconductors. We investigate the ultrafast quasiparticle (QP) dynamics of an intercalated superconductor (Li1 – x
Fe
x
)OHFe1 – y
Se, which is a bulk crystal but shares a similar electronic structure with single-layer FeSe on SrTiO3. We obtain the electron-phonon coupling (EPC) constant λ
A
1g
(0.22 ± 0.04), which well bridges that of bulk FeSe crystal and single-layer FeSe on SrTiO3. Significantly, we find that such a positive correlation between λ
A
1g
and superconducting T
c holds among all known FeSe-based superconductors, even in line with reported FeAs-based superconductors. Our observation indicates possible universal role of EPC in the superconductivity of all known categories of iron-based superconductors, which is a critical step towards achieving a unified superconducting mechanism for all iron-based superconductors.
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