Carbon‐Based Metal‐Free Catalysts for Electrocatalysis beyond the ORR

Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon‐based metal‐free catalysts have also been demonstrated to be promising alternatives to noble‐metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal–air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon‐based metal‐free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal‐free electrocatalysis.     

New diagnostic of the most populated conformer of tetrahydrofuran in the gas phase

The most populated conformer of tetrahydrofuran (C(4)H(8)O) has been diagnosed as the Cs conformer in the present study, jointly using experimental electron momentum spectroscopy (EMS) and quantum mechanics. Our B3LYP/6-311++G** model indicates that the C1 conformation, which is one of the three possible conformations of tetrahydrofuran produced by pseudorotation in the gas phase, is a transition state due to its imaginary frequencies, in agreement with the prediction from a recent ab initio MP2/aug-cc-pVTZ study (J. Chem. Phys. 2005, 122, 204303). The study has identified the fingerprint of the highest occupied molecular orbital (HOMO) of the C(s) (12a') conformer as the most populated conformer. The identification of the C(s) structure, therefore, leads to the orbital-based assignment of the ionization binding energy spectra of tetrahydrofuran for the first time, on the basis of the outer valence Green function OVGF/6-31G* model and the density functional theory (DFT) SAOP/ET-PVQZ model. The present study explores an innovative approach to study molecular stabilities. It also indicates that energetic properties are not always the most appropriate means to study conformer-rich biological systems.     

Controlled green synthesis of Au–Pt bimetallic nanoparticles using chlorogenic acid

Research on Chemical Intermediates - Well-dispersed Au–Pt alloyed bimetallic nanoparticles are synthesized using chlorogenic acid as the only reducing agent and stabilizer to reduce Au/Pt...     

Facile synthesis of hollow palladium/copper alloyed nanocubes for formic acid oxidation

Hollow PdCu alloyed nanocubes were successfully synthesized by a novel one-pot template-free strategy through tuning the surface energy difference of the crystal planes by alloying. Compared with the solid nanoparticles, the hollow nanocubes exhibit superior electrocatalytic activity and stability for formic acid oxidation.     

Mechanical stability and transport properties of the Sn-promoted SrCo0.8Fe0.2O3−δ ceramic membrane

In this article, the phase compositions, thermal, mechanical and transport properties of both the SrCo_0.8Fe_0.2O_3−δ (SCF) and the SrCo_0.8Fe_0.1Sn_0.1O_3−δ (SSCF) ceramic membranes were investigated systematically. As compared with the SCF membrane, the SSCF one had a more promoted thermal shock resistance, which related to its small thermal expansion coefficient between them and an enhanced composite structure for it. For the SCF membrane, a permeation rate of 1.9 × 10⁻⁶ mol cm⁻² s⁻¹ was obtained at 1000 °C and under the oxygen partial pressure gradient of P_O2 (h)/P_O2 (l) = 0.209 atm/0.012 atm; however, the permeation rate was 2.5 × 10⁻⁶ mol cm⁻² s⁻¹ for the SSCF one in the same measuring condition. In addition, both peak values of total electrical conductivity (σ_e) for SSCF sample appeared with increasing temperature. The second peak value of σ_e for SSCF one was regarded as the contribution from its minor phase, which appeared with the mixed conducting behavior resulting from partly Co-dissolving into its lattice.     

一种广义插值法

本文考虑一种广义插值问题，插值条件为小区间上的积分值，以弥补现有的插值方法在L2空间不再适用的不足，除了多项式插值外，还讨论了两种一次样条插值方法。     

Electrical and electrochemical properties of SrBiMTiO<Subscript>6</Subscript> (M = Fe,Mn, Cr) as potential cathodes for solid oxide fuel cells

A series of perovskite oxides SrBiMTiO₆ (M = Fe, Mn, Cr) have been synthesized and characterized towards application as cathode materials for solid oxide fuel cells (SOFCs). X-ray diffraction (XRD) patterns reveal that all samples are stabilized in \( \mathrm{Pm}\ \overline{3}\mathrm{m} \) space group. Electrical conductivity, AC impedance characteristics, and thermal and chemical stability have been studied in order to assess their possible use as SOFC cathode materials. In comparison with other low electrical conductivity cathodes of SOFC, our results suggest that SrBiMnTiO₆, which has the highest electrical conductivity (4.02 S cm^?1) and moderate polarization resistance (0.104 Ω cm²) at 850 °C, is the most promising candidate among the three perovskite oxides for further study and optimization as a SOFC cathode material.     

Synthesis and characterization of Pd catalysts supported on carbon microspheres for formic acid oxidation

A facile preparation of Pd catalyst using carbon microspheres as support was introduced in this paper. The carbon microspheres were prepared with a simple method from dextrose via hydrothermal process and used as catalysts support for formic acid electrooxidation. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that the as-prepared face-centered cubic crystal Pd nanoparticles were well-dispersed on the surface of the carbon microspheres, and the mean diameter of the nanoparticles was 8.8 nm. The effect of the support on the catalyst performance for formic acid electrooxidation was studied. The as-prepared catalyst showed the enhanced electrochemical surface active area and the higher electrocatalytic activity towards formic acid oxidation compared with Pd/CNTs and Pd/XC-72 catalysts prepared at room temperature. Electrochemical analysis suggested that the carbon microspheres might be good candidates to be used as the supports of catalyst for formic acid electrochemical oxidation.     

Three‐Dimensional Macroporous NiCo2O4 Sheets as a Non‐Noble Catalyst for Efficient Oxygen Reduction Reactions

A facile and low‐cost strategy is developed to prepare three‐dimensional (3D) macroporous NiCo₂O₄ sheets, which can be used as a highly efficient non‐noble metal electrocatalyst for the oxygen reduction reaction (ORR) in alkaline conditions. The as‐obtained sheets have a thickness of about 150 nm and feature a typical 3D macroporous structure with pore volumes of up to 0.23 cm³ g^?1, which could decrease the mass transport resistance and allow easier access of the reactants to the active surface sites. The as‐prepared macroporous NiCo₂O₄ sheets exhibit high electrocatalytic activity for ORR with a four‐electron pathway, good long‐term stability and high tolerance against methanol. The unique 3D macroporous structure and intrinsic properties may be responsible for their high performance.