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The one-step electrochemical synthesis of H 2 O 2 is an on-site method that reduces dependence on the energy-intensive anthraquinone process. Oxidized carbon materials have proven to be promising catalysts due to their low cost and facile synthetic procedures. However, the nature of the active sites is still controversial, and direct experimental evidence is presently lacking. Here, we activate a carbon material with dangling edge sites and then decorate them with targeted functional groups. We show that quinone-enriched samples exhibit high selectivity and activity with a H 2 O 2 yield ratio of up to 97.8 % at 0.75 V vs. RHE. Using density functional theory calculations, we identify the activity trends of different possible quinone functional groups in the edge and basal plane of the carbon nanostructure and determine the most active motif. Our findings provide guidelines for designing carbon-based catalysts, which have simultaneous high selectivity and activity for H 2 O 2 synthesis. The identity of catalytic sites for H 2 O 2 generation in carbon-based materials remains controversial with limited experimental evidence to date. Here, the authors decorate various target functional groups on carbon materials and quinone-enriched samples exhibit the highest activity and selectivity.

Ammonia, one of the most important synthetic feedstocks, is mainly produced by the Haber–Bosch process at 400–500 °C and above 100 bar. The process cannot be performed under ambient conditions for kinetic reasons. Here, we demonstrate that ammonia can be synthesized at 45 °C and 1 bar via a mechanochemical method using an iron-based catalyst. With this process the ammonia final concentration reached 82.5 vol%, which is higher than state-of-the-art ammonia synthesis under high temperature and pressure (25 vol%, 450 °C, 200 bar). The mechanochemically induced high defect density and violent impact on the iron catalyst were responsible for the mild synthesis conditions. The ammonia was synthesized under ambient conditions via a mechanochemical method, reaching a final concentration of 82.5 vol%.

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency. Instead of only adjusting the electronic structure, here we utilize ferroelectric polarization to accelerate the oxygen evolution reaction as well. This is demonstrated on a multiferroic layered perovskite Bi 5 CoTi 3 O 15 with in-situ grown BiCoO 3 . Thanks to the superimposed effects of electronic regulation and ferroelectric polarization, the as-prepared multiferroic electrocatalysts are more efficient than the benchmark IrO 2 (with a final 320 mV overpotential at the current density of 10 mA cm −2 and a 34 mV dec −1 Tafel slope). This work not only demonstrates a low-cost and high-efficient OER electrocatalyst, but also provides a strategic design for multi-component electrocatalytic material systems by consideration of both spin and polarization degrees of freedom. While splitting water into fuel may provide a green, renewable method for energy storage, water oxidation is its bottleneck. Here, authors reported multiferroic electrocatalysts with improved oxygen evolution performances assisted by polarization.

Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction (HER) catalysis. The HER reaction rate is a trade-off between hydrogen adsorption and desorption on the catalyst surface. Herein, we report the rational balancing of hydrogen adsorption/desorption by orbital modulation using introduced environmental electronegative carbon/nitrogen (C/N) atoms. Theoretical calculations reveal that the empty d orbitals of iridium (Ir) sites can be reduced by interactions between the environmental electronegative C/N and Ir atoms. This balances the hydrogen adsorption/desorption around the Ir sites, accelerating the related HER process. Remarkably, by anchoring a small amount of Ir nanoparticles (7.16 wt%) in nitrogenated carbon matrixes, the resulting catalyst exhibits significantly enhanced HER performance. This includs the smallest reported overpotential at 10 mA cm −2 (4.5 mV), the highest mass activity at 10 mV (1.12 A mg Ir −1 ) and turnover frequency at 25 mV (4.21 H 2 s −1 ) by far, outperforming Ir nanoparticles and commercial Pt/C. Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction catalysis. Here, the authors demonstrate the rational balancing of hydrogen adsorption/desorption by orbital modulation for significantly enhanced hydrogen evolution performance.

Coherent excitation and control of lattice motion by electromagnetic radiation in optical frequency range has been reported through variety of indirect interaction mechanisms with phonon modes. However, coherent phonon excitation by direct interaction of electromagnetic radiation and nuclei has not been demonstrated experimentally in terahertz (THz) frequency range mainly due to the lack of THz emitters with broad bandwidth suitable for the purpose. We report the experimental observation of coherent phonon excitation and detection in GaAs using ultrafast THz-pump/optical-probe scheme. From the results of THz pump field dependence, pump/probe polarization dependence, and crystal orientation dependence, we attributed THz wave absorption and linear electro-optic effect to the excitation and detection mechanisms of coherent polar TO phonons. Furthermore, the carrier density dependence of the interaction of coherent phonons and free carriers is reported.

Identification of active sites is one of the main obstacles to rational design of catalysts for diverse applications. Fundamental insight into the identification of the structure of active sites and structural contributions for catalytic performance are still lacking. Recently, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) provide important tools to disclose the electronic, geometric and catalytic natures of active sites. Herein, we demonstrate the structural identification of Zn-N 2 active sites with both experimental/theoretical X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Further DFT calculations reveal that the oxygen species activation on Zn-N 2 active sites is significantly enhanced, which can accelerate the reduction of oxygen with high selectivity, according well with the experimental results. This work highlights the identification and investigation of Zn-N 2 active sites, providing a regular principle to obtain deep insight into the nature of catalysts for various catalytic applications. Identification of active sites is one of the main obstacles to rational design of catalysts for scientific and industrial applications. Here, the authors demonstrate the synthesis and structural identification of Zn based active sites, as well as the related structural activation for oxygen species.

Ferromagnetic insulators are required for many new magnetic devices, such as dissipationless quantum-spintronic devices, magnetic tunneling junctions, etc. Ferromagnetic insulators with a high Curie temperature and a high-symmetry structure are critical integration with common single-crystalline oxide films or substrates. So far, the commonly used ferromagnetic insulators mostly possess low-symmetry structures associated with a poor growth quality and widespread properties. The few known high-symmetry materials either have extremely low Curie temperatures (≤16 K), or require chemical doping of an otherwise antiferromagnetic matrix. Here we present compelling evidence that the LaCoO₃ single-crystalline thin film under tensile strain is a rare undoped perovskite ferromagnetic insulator with a remarkably high T C of up to 90 K. Both experiments and first-principles calculations demonstrate tensile-strain–induced ferromagnetism which does not exist in bulk LaCoO₃. The ferromagnetism is strongest within a nearly stoichiometric structure, disappearing when the Co2+ defect concentration reaches about 10%. Significant impact of the research includes demonstration of a strain-induced high-temperature ferromagnetic insulator, successful elevation of the transition over the liquid-nitrogen temperature, and high potential for integration into large-area device fabrication processes.

The ligand engineering of inorganic lead halide perovskite quantum dots (PQDs) is an indispensable strategy to boost their photoluminescence stability, which is pivotal for optoelectronics applications. CsPbX3 (X = Cl, Br, I) PQDs exhibit exceptional optical properties, including high color purity and tunable bandgaps. Despite their promising characteristics, environmental sensitivity poses a challenge to their stability. This article reviews the solution-based synthesis methods with ligand engineering. It introduces the impact of factors like humidity, temperature, and light exposure on PQD’s instability, as well as in situ and post-synthesis ligand engineering strategies. The use of various ligands, including X- and L-type ligands, is reviewed for their effectiveness in enhancing stability and luminescence performance. Finally, the significant potential of ligand engineering for the broader application of PQDs in optoelectronic devices is also discussed.

With the CoO2 slabs consisting of Co4O4 cubane structure, layered NaxCoO2 are considered promising candidates for oxygen evolution reaction (OER) in alkaline media given their earth‐abundant and structural advantages. However, due to the strong adsorption of intermediates on the large basal planes, NaxCoO2 cannot meet the activity demands. Here, a novel one‐pot synthesis strategy is proposed to realize the high solubility of iron in NaxCoO2 in an air atmosphere. The optimist Na0.6Co0.9Fe0.1O2 exhibits enhanced OER activity compared to their pristine and other reported Fe‐doped NaxCoO2 counterparts. Such an enhancement is mainly ascribed to the abundant active sites on the activated basal planes and the participation of oxidized oxygen as active sites independently, which breaks the scaling relationship limit in the OER process. This work is expected to contribute to the understanding of the modification mechanism of Fe‐doped cobalt‐based oxides and the exploitation of layer‐structured oxides for energy application. The incorporation of Fe into CoO2 slabs significantly improve the oxygen evolution reaction (OER) activity of layered Na0.6CoO2. The enhancement is mainly ascribed to the enriched active sites on the activated basal planes and the participation of oxidized oxygen as active sites independently, which breaks the scaling relationship limit in the OER process.

Antiferromagnets have attracted considerable interest in the field of spintronics due to their attractive characteristics such as ultrafast spin dynamics and robustness against external magnetic field perturbations. Sr2IrO4 is a rare example of antiferromagnetic semiconductor oxide and has been extensively studied in anisotropic magnetoresistance-based spintronics. However, the anisotropic magnetoresistance of Sr2IrO4 films is usually very small. Herein, we have prepared a (Sr2IrO4)4/(La2/3Sr1/3MnO3)5 superlattice which shows an enhanced anisotropic magnetoresistance compared to Sr2IrO4 film or La2/3Sr1/3MnO3/Sr2IrO4 heterostructure and an obvious nonvolatile memory effect that is comparable to Sr2IrO4 single crystals. Through magnetic measurements, the increased coercivity and the exchange bias at low temperatures reveal the interfacial magnetic coupling between Sr2IrO4 and La2/3Sr1/3MnO3. Additionally, the remarkable anisotropic magnetoresistance and clear hysteresis of anisotropic magnetoresistance with distinct fourfold symmetry can be controlled by temperature and magnetic field. These findings demonstrate that the superlattices of heavy transition metal oxide Sr2IrO4 are excellent platforms for antiferromagnetic spintronics.