Qiuyan Hao

The development of stable and efficient electrocatalysts for oxygen evolution reaction is of great significance for electro-catalytic water splitting. Bimetallic layered double hydroxides (LDHs) are promising OER catalysts, in which NiCu LDH has excellent stability compared with the most robust NiFe LDH, but the OER activity is not satisfactory. Here, we designed a NiCu LDH heterostructure electrocatalyst (Cu/NiCu LDH) modified by Cu nanoparticles which has excellent activity and stability. The Cu/NiCu LDH electrocatalyst only needs a low over-potential of 206 mV and a low Tafel slope of 86.9 mV dec⁻¹ at a current density of 10 mA cm⁻² and maintains for 70 h at a high current density of 100 mA cm^–2 in 1M KOH. X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic interaction between Cu nanoparticles and NiCu LDH. Density functional theory (DFT) calculations show that the electronic coupling between Cu nanoparticles and NiCu LDH can effectively improve the intrinsic OER activity by optimizing the conductivity and the adsorption energy of oxygen-containing intermediates.

Heazlewoodite, Ni ₃ S ₂ , is one of the most promising bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media due to its metallic conductivity and low cost.

The development of earth-abundant and low-cost electrocatalysts with high performance toward the oxygen evolution reaction (OER) plays a key role in water splitting. Here, a novel OER electrocatalyst of Ni–Fe–OH/Ni₃S₂ nanoparticles on Ni foam (Ni–Fe–OH/Ni₃S₂/NF) was synthesized by a facile, ultrafast two-step method within 2 minutes. The obtained Ni–Fe–OH/Ni₃S₂/NF catalyst presents an excellent OER performance, only requiring a low overpotential of 268 mV to reach a current density of 10 mA cm⁻² and a small Tafel slope of 54 mV dec⁻¹ in 1 M KOH, which was sustained for 12 h at a current density of 175 mA cm⁻² almost without any degradation. The superior OER performance of the Ni–Fe–OH/Ni₃S₂/NF catalyst is attributed to the increased active sites, the accelerated electron transfer between the electrode and electrolyte, and the synergistic effect between amorphous Ni–Fe–OH and Ni₃S₂. This work opens up a new avenue for preparing highly efficient heterostructure electrocatalysts toward the OER.

A simple method is developed for the preparation of MoSe₂/MoO₂ composite with a flower-like structure for high-performance lithium-ion batteries (LIBs). MoSe₂ could lead to fast and facile movement of Li⁺ due to its larger interlayer spacing. Meanwhile, MoO₂ could protect the lamellar structure of MoSe₂ from being destroyed in the charging/discharging processes to maintain the required active surface to electrolytes. In addition, the flower-like structure of the composite could effectively alleviate the volume expansion during charging/discharging. As LIBs are anode material, MoSe₂/MoO₂ composite demonstrates an excellent specific discharge capacity of 1042 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹, which is attributed to the synergistic effects of MoSe₂ and MoO₂ in the composite.

In this paper, the synthesis of the three-dimensional (3D) composite of spherical reduced graphene oxide (RGO) with uniformly distributed CeO₂ particles is reported. This synthesis is done via a facile and large-scalable spray-drying process, and the CeO₂/RGO materials are hydrothermally compounded with sulfur. The morphology, composition, structure, and electrochemical properties of the 3D S/CeO₂/RGO composite are studied using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), Raman spectra and X-ray photoelectron spectroscopy (XPS), etc. The electrochemical performance of the composites as electrodes for lithium–sulfur batteries is evaluated. The S/CeO₂/RGO composites deliver a high initial capacity of 1054 mAh g⁻¹, and retain a reversible capacity of 792 mAh g⁻¹ after 200 cycles at 0.1 C. Profiting from the combined effect of CeO₂ and RGO, the CeO₂/RGO materials effectively inhibit the dissolution of polysulfides, and the coating of spherical RGO improves the structural stability as well as conductivity.

Hybrid organic-inorganic perovskite materials have attracted extensive attention due to their impressive performance in photovoltaic devices. One-dimensional perovskite CH₃NH₃PbI₃ nanomaterials, possessing unique structural features such as large surface-to-volume ratio, anisotropic geometry and quantum confinement, may have excellent optoelectronic properties, which could be utilized to fabricate high-performance photodetectors. However, in comparison to CH₃NH₃PbI₃ thin films, reports on the fabrication of CH₃NH₃PbI₃ nanowires for optoelectrical application are rather limited. Herein, a two-step spin-coating process has been utilized to fabricate pure-phase and single-crystalline CH₃NH₃PbI₃ nanowires on a substrate without mesoporous TiO₂ or Al₂O₃. The size and density of CH₃NH₃PbI₃ nanowires can be easily controlled by changing the PbI₂ precursor concentration. The as-prepared CH₃NH₃PbI₃ nanowires are utilized to fabricate photodetectors, which exhibit a fairly high switching ratio of ~600, a responsivity of 55 mA/W, and a normalized detectivity of 0.5 × 10¹¹ jones under 532 nm light illumination (40 mW/cm²) at a very low bias voltage of 0.1 V. The as-prepared perovskite CH₃NH₃PbI₃ nanowires with excellent optoelectronic properties are regarded to be a potential candidate for high-performance photodetector application.

A fast and facile ambient pressure solution chemical process was applied to grow chalcopyrite CuInSe₂ nanoparticles by using common and inexpensive polylol ethylene glycol(EG), diethylene glycol(DEG) and triethylene glycol(TEG) as solvent, copper(II) chloride, indium(III) chloride and selenium powder as precursors, hydrazine hydrate and ethylenediamine as reducing agent and polyvinylpyrrolidone as capping agent. The products synthesized were characterized by XRD, TEM, HRTEM, EDS and UV-vis measurements based on different solvents EG, DEG and TEG, refluxing temperature and time as well as PVP adding amounts. The well-dispersed and single-phase CuInSe₂ nanoparticles synthesized with TEG solvent were used to prepare nanoparticles colloidal ink by ultrasonically dispersing in absolute alcohol solvent and then deposit CuInSe₂ thin films by layer-by-layer dip-coating nanoparticles ink. The deposited thin films were annealed in Ar atmosphere at 550°C for 30 min. Photovoltaic test devices with Mo-coated glass/CuInSe₂/CdS/i-ZnO/AZO configuration were fabricated using the ink-coated and annealed CuInSe₂ light-absorbing thin films, and the corresponding I-V characteristics were evaluated.

N-type InGaN/GaN multiple-quantum-wells (MQWs) were grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The crystal quality and optical properties of samples after rapid thermal annealing (RTA) at different temperatures in a range from 400 to 800°C are investigated by X-ray diffraction (XRD) and photoluminescence (PL) spectrum. The experimental results show that the peaks of InGaN, InN and In can be observed in all samples. And the results are induced by the phase separation and In-clusters. The luminescence peak of the samples annealed showed a red shift. It is caused by strain stress relaxation during the RTA process. Furthermore, some defects can be eliminated and the best annealing temperature is from 500°C to 700°C.

The changes of flow pattern defects (FPDs), one kind of grown-in defects in CZ-Si, in RTA annealed wafers were investigated in this paper. The wafers were rapid thermal annealed in N/sub 2/, N/sub 2//O/sub 2/ and Ar atmosphere respectively under RTA processes. A void was found on the apex of the parabola outline of FPDs by AFM and optical microscopy. It's shown that the hole on the tip of FPDs became shallower in depth and larger in width obviously when annealed above 1100/spl deg/C, esp. annealed in Ar atmosphere 1200/spl deg/C. Furthermore, it's also shown that the density of FPDs to reduce when annealed above 1100/spl deg/C, and most of FPDs in CZ-Si would disappear during RTA process in Ar atmosphere above 1200/spl deg/C.