One-pot synthesis of bismuth yttrium tungstate nanosheet decorated 3D-BiOBr nanoflower heterostructure with enhanced visible light photocatalytic activity

A visible light driven BiOBr/Bi_xY_1-xWO₆ nanocomposite photocatalyst of various compositions are prepared by the addition of different amounts of KBr (0.5, 1.0, 1.5, 2.0 mmol) in Bi_xY_1-xWO₆ by a one-pot hydrothermal method. Furthermore, the photocatalytic properties of the as-prepared materials are analyzed by the decomposition of methylene blue under visible light illumination. In particular, the BiOBr/Bi_xY_1-xWO₆ nanocomposite prepared by taking 1.5 mmol of KBr present a superior photocatalytic ability (78.3%) with the rate constant value 0.016 min^-1, a low bandgap (E_g = 2.51 eV) as well as photoluminescence emission intensity than other photocatalysts prepared in this study. The radical scavenging studies revealed that OH and h⁺ performed an imperative role in the decomposition of methylene blue. Furthermore, the optimized photocatalyst is stable even after four cycles, which exposes the excellent photostability and reusability properties of the photocatalyst. In addition, a plausible mechanism of decomposition of methylene blue under visible light irradiation is also proposed.

Heterostructure Ni3S4-MoS2 with interfacial electron redistribution used for enhancing hydrogen evolution

Developing highly effective and inexpensive electrocatalysts for hydrogen evolution reaction (HER), particularly in a water-alkaline electrolyzer, are crucial to large-scale industrialization. The earth-abundant molybdenum disulfide (MoS₂) is an ideal electrocatalyst in acidic media but suffers from a high overpotential in alkaline solution. Herein, nanospherical heterostructure Ni₃S₄-MoS₂ was obtained via a one-pot synthesis method, in which Ni₃S₄ was uniformly integrated with MoS₂ ultrathin nanosheets. There were abundant heterojunctions in the as-synthesized catalyst, which were verified by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The structure features with interfacial electron redistribution was proved by XPS and density functional theory (DFT) calculations, which offered several advantages to promote the HER activity of MoS₂, including increased specific surface area, exposed abundant active edge sites and improved electron transfer. Ni₃S₄-MoS₂ exhibited a low overpotential of 116 mV at 10 mA cm^-2 in an alkaline solution with a corresponding Tafel slope of 81 mV dec^-1 and long-term stability of over 20 h. DFT simulations indicated that the synergistic effects in the system with the chemisorption of H on the (002) plane of MoS₂ and OH on the (311) plane of Ni₃S₄ accelerated the rate-determining water dissociation steps of HER. This study provides a valuable route for the design and synthesis of inexpensive and efficient HER electrocatalyst, heterostructure Ni₃S₄-MoS₂.

Interface engineering of a hierarchical ZnxCd1-xS architecture with favorable kinetics for high-performance solar water splitting

Manipulating the charge carrier transport in photoactive materials is a big challenge toward high efficiency solar water splitting. Herein, we designed a hierarchical ZnxCd1-xS architecture for tuning the interfacial charge transfer kinetics. The in situ growth of ZnxCd1-xS nanoflakes on ZnO backbones provided low interfacial resistance for charge separation. With this special configuration, the optimized Zn0.33Cd0.67S photoanode achieved significantly enhanced performance with a photocurrent density of 10.67 mA cm-2 at 1.23 V versus RHE under AM1.5G solar light irradiation, which is about 14.1 and 2.5 times higher than that of the pristine ZnO and CdS nanoparticle decorated ZnO photoanodes, respectively. After coating a thin SiO2 layer, the photostability of the hierarchical Zn0.33Cd0.67S photoanode is greatly enhanced with 92.33% of the initial value retained under 3600 s continuous light illumination. The prominent PEC activity of the hierarchical ZnxCd1-xS nanorod arrays can be ascribed to an enhanced charge transfer rate aroused by the binder-free interfacial heterojunction, and the improved reaction kinetics at the electrode-electrolyte interface, which is evidenced by electrochemically active surface area measurements and intensity modulated photocurrent spectroscopy analysis. This interfacial heterojunction strategy provides a promising pathway to prepare high performance photoelectrodes.

Explanation for the conductivity difference of half-Heusler transparent conductors via ionization energy

To further understand the less-studied half-Heusler transparent conductors, we have considered four 18-electron ABX compounds (TaIrGe, TaIrSn, ZrIrSb, and TiIrSb) to focus on their carrier effective masses and ionization energies. The novelty of this work lies in two aspects: (i) we discover that hole-killer defects are more likely to form in TaIrGe than in ZrIrSb, which leads to a lower concentration of the holes in TaIrGe. This is the fundamental reason for the conductivity of TaIrGe being much lower than that of ZrIrSb; (ii) we propose that the hole effective mass near the sub-valence band maximum (Sub-VBM) could be used to forecast the potential transport performance of the materials. The obtained results show that the transport performance of TaIrGe & TaIrSn is potentially more promising than that of TiIrSb and ZrIrSb. Besides, this work firstly studies the mechanical properties of the considered ABX compounds, offering strong evidence that TaIrGe, TaIrSn, ZrIrSb, and TiIrSb could be potentially flexible and ductile TCMs.