The thermoelectric figure-of-merit (ZT) for GeTe powder is able to be raised from ∼0.8 to 1.37 at high temperature near ∼500 °C by tuning the Ge vacancy level through a reversible in situ route.
An optimized two-step melt-quenching synthesis method is proposed for GeTe to show a highly reproducible high ZT ∼ 2.35 at 800 K (in Ge0.9Sb0.1Te) through simultaneous carrier concentration and microstructural control.
Tuning
the electronic structure of perovskite oxides via aliovalent
substitution is a promising strategy to attain inexpensive and efficient
electrocatalysts for energy conversion and storage devices. Herein,
following the d-band center positions and using a simple sol–gel
method followed by a pyrolysis step, LaNi1–x
Co0.5x
Fe0.5x
O3 (LNFCO-x; x = 0.0, 0.4, 0.5, and 0.6) electrocatalysts are designed and synthesized
for oxygen redox reactions in 1 M KOH. Among them, LNFCO-0.5 has exhibited
the lowest overpotential and the highest charge transfer kinetics
in oxygen redox reactions. Overall, a 90 mV lower overpotential was
observed in oxygen redox activity of LNFCO-0.5 compared to that of
pristine LaNiO3. The mass activity of LNFCO-0.5 in the
oxygen reduction reaction (at 0.7 V vs RHE) and oxygen evolution reaction
(1.60 V vs RHE) was calculated to be 2.5 and 2.13 times higher than
that of LaNiO3, respectively. The bifunctionality index
(potential difference between the oxygen evolution at a current density
of 10 mA cm–2 and the oxygen reduction at a current
density of −1 mA cm–2) of LNFCO-0.5 was found
to be 0.98. The substitution of Fe and Co for the Ni-site shifted
the d-band center close to the Fermi level, which can increase the
binding strength of the *OH intermediate in the rate-determining step.
Also, the surface was enriched with Fe3+Δ, Co3+, and partially oxidized Ni3+ states, which is
susceptible to tune the eg-orbital filling for superior
oxygen redox activity.
The crystal structure and magnetic, electronic, and thermal properties of a NdSbTe single crystal were examined by X-ray diffraction, magnetic and specific heat C p (T) measurements, and density functional theory (DFT) calculations. NdSbTe undergoes an antiferromagnetic ordering at T N ≈ 2.9 K, which is obviously shown from χ(T) and C p (T). With increasing H, a spinflop transition is induced along the c axis, and subsequently AFM disappeared at H ≤ 0.4 T and H ≤ 2.5 T along H||c and H||ab, respectively. This remarkable observation shows that the ordered Nd 3+ moments lie in the c axis and that there is the existence of an anisotropy scenario. The estimated magnetic anisotropy with χ ||c (0.63)/χ ||ab (0.036) is 17.5 at temperature 1.8 K. An analysis of specific heat capacity reveals the significant contribution of crystal field effects at high temperature. We carried out DFT calculations to predict the magnetic ground state and the electronic properties of NdSbTe. Our calculations revealed that the magnetic ground state is AFM with spins aligned ferromagnetically along the b axis and antiferromagnetically along the c axis. The calculated electronic band of NdSbTe exhibits a Dirac semimetal material nature.
Developing a non-precious metal electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is desirable for low-cost energy conversion devices. Herein, we designed and developed a new class...
Making semiconductor radiation detectors that work at
room temperature
relies heavily on the deposition and pixelation of electrodes. Electrode
patterning of perovskite solar cells widely implements laser scribing
techniques, which is a convenient, scalable, and inexpensive technique.
However, this method has not found its application in radiation detector
patterning yet, and the question whether laser scribing can achieve
high-quality patterns with minimum damage to a detector crystal and
low interpixel cross-talk remains largely unanswered. To prove that
laser scribing is a practical method for electrode patterning on perovskite
CsPbBr3 detectors, we use the material to create a variety
of patterns. A very low lateral leakage current (60 nA at 10 V) and
high mobility-lifetime product (9.7(3) × 10–4 cm2/V) were observed between the pixel and the guard
ring in tests of single-pixel devices with a separation of 200 or
100 μm between the central electrode and the guard ring. The
122 and 136 keV photopeaks in 57Co gamma-ray spectra were
very well resolved with an energy resolution of up to 6.1% at 122
keV. A further reduction in gap size to 50 μm is conceivable,
but more process optimization is needed.
Atomically dispersed iron sites on nitrogen‐doped carbon (Fe‐NC) are the most active Pt‐group‐metal‐free catalysts for oxygen reduction reaction (ORR). However, due to oxidative corrosion and the Fenton reaction, Fe‐NC catalysts are insufficiently active and stable. Herein, w e demonstrated that the axial Cl‐modified Fe‐NC (Cl‐Fe‐NC) electrocatalyst is active and stable for the ORR in acidic conditions with high H2O2 tolerance. The Cl‐Fe‐NC exhibits excellent ORR activity, with a high half‐wave potential (E1/2) of 0.82 V versus a reversible hydrogen electrode (RHE), comparable to Pt/C (E1/2 = 0.85 V versus RHE) and better than Fe‐NC (E1/2 = 0.79 V versus RHE). X‐ray absorption spectroscopy analysis confirms that chlorine is axially integrated into the FeN4. More interestingly, compared to Fe‐NC, the Fenton reaction is markedly suppressed in Cl‐Fe‐NC. In situ electrochemical impedance spectroscopy reveals that Cl‐Fe‐NC provides efficient electron transfer and faster reaction kinetics than Fe‐NC. Density functional theory calculations reveal that incorporating Cl into FeN4 can drive the electron density delocalization of the FeN4 site, leading to a moderate adsorption free energy of OH* (∆GOH*), d‐band center, and a high onset potential, and promotes the direct four‐electron‐transfer ORR with weak H2O2 binding ability compared to Cl‐free FeN4, indicating superior intrinsic ORR activity.
Solvent-dependent magnetism in Cu-based metal–organic frameworks (MOFs) is reported. The spin-flop magnetic behaviour occurs at different dehydrated states of the MOF. The oxygens of guest and coordinated water molecules are...
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