Band-Gap Tunable 2D Hexagonal (GaN)1-x(ZnO)x Solid-Solution Nanosheets for Photocatalytic Water Splitting

Study on the effects of strain and electrostatic doping on the magnetic anisotropy of GaN/VTe2van der waals heterostructure

Using a first-principles approach, this study delves into the effects of strain and electrostatic doping on the electronic and magnetic properties of the GaN/VTe2van der Waals (vdW) heterostructure. The results reveal that when the GaN/VTe2vdW heterostructure is doped with 0.1h/0.2hof electrostatic charge, its magnetization direction undergoes a remarkable reversal, shifting from out-of-plane orientation to in-plane direction. Therefore, we conduct a thorough investigation into the influence of electron orbitals on magnetic anisotropy energy. In addition, as the strain changes from -1% to 1%, the 100% spin polarization region of the GaN/VTe2vdW heterostructure becomes smaller. It is worth noting that at a doping concentration of 0.1h, the GaN/VTe2vdW heterostructure has a Curie temperature of 30 K above room temperature. This comprehensive study provides valuable insights and provides a reference for analyzing the electronic and magnetic properties of low-dimensional systems.

Surprising Effects of Ti and Al2O3 Coatings on Tribocatalytic Degradation of Organic Dyes by GaN Nanoparticles

GaN is more stable than most metal oxide semiconductors for the photocatalytic degradation of organic pollutants in harsh conditions, while its catalytic efficiency has been difficult to be substantially improved. In this study, the tribocatalytic degradation of organic dyes by GaN nanoparticles has been investigated. Stimulated through magnetic stirring using homemade Teflon magnetic rotary disks in glass beakers, the GaN nanoparticles were found to induce negligible degradation in rhodamine B (RhB) and methyl orange (MO) solutions. Surprisingly, the degradation was greatly enhanced in beakers with Ti and Al2O3 coatings on their bottoms: 99.2% and 99.8% of the 20 mg/L RhB solutions were degraded in 3 h for the Ti and Al2O3 coatings, respectively, and 56% and 60.2% of the 20 mg/L MO solutions were degraded in 24 h for the Ti and Al2O3 coatings, respectively. Moreover, the MO molecules were only broken into smaller organic molecules for the Ti coating, while they were completely degraded for the Al2O3 coating. These findings are important for the catalytic degradation of organic pollutants by GaN in harsh environments and for achieving a better understanding of tribocatalysis as well.

Applications of BiOX in the Photocatalytic Reactions

BiOX (X = Cl, Br, I) families are a kind of new type of photocatalysts, which have attracted the attention of more and more researchers. The suitable band gaps and their convenient tunability via the change of X elements enable BiOX to adapt to many photocatalytic reactions. In addition, because of their characteristics of the unique layered structure and indirect bandgap semiconductor, BiOX exhibits excellent separation efficiency of photogenerated electrons and holes. Therefore, BiOX could usually demonstrate fine activity in many photocatalytic reactions. In this review, we will present the various applications and modification strategies of BiOX in photocatalytic reactions. Finally, based on a good understanding of the above issues, we will propose the future directions and feasibilities of the reasonable design of modification strategies of BiOX to obtain better photocatalytic activity toward various photocatalytic applications.

Narrow-Band Solar-Blind Ultraviolet Detectors Based on AlSnO Films with Tunable Band Gap

Semiconductor materials with sufficiently wide band gaps are urgently desired for use in solar-blind ultraviolet detectors. In this work, the growth of AlSnO films was achieved through the magnetron sputtering technique. AlSnO films with band gaps in the range of 4.40-5.43 eV were obtained by varying the growth process, which demonstrates that the band gap of AlSnO is continuously tunable. What is more, based on the films prepared, narrow-band solar-blind ultraviolet detectors were fabricated with good solar-blind ultraviolet spectral selectivity, excellent detectivity, and narrow full widths at half-maximum in the response spectra, showing a great potential to be applied to solar-blind ultraviolet narrow-band detection. Therefore, based on the results above, this study focusing on the fabrication of detectors via band gap engineering can be a significant reference for researchers interested in solar-blind ultraviolet detection.

Electrospinning Preparation of GaN:ZnO Solid Solution Nanorods with Visible-Light-Driven Photocatalytic Activity toward H2 Production

The development of a facile method for the synthesis of GaN:ZnO solid solution, an attractive material with a wurtzite-type structure, is vital to enhance its photocatalytic activity toward H2 evolution. Herein, GaN:ZnO solid solution nanorods with diameters of around 180 nm were fabricated by combining the electro-spun method with a sequentially calcinating process. Photocatalytic water-splitting activities of the as-obtained samples loaded with Rh2−yCryO3 co-catalyst were estimated by H2 evolution under visible-light irradiation. The as-prepared GaN:ZnO nanorods at a nitridation temperature of 850 °C showed the optimal performance. Careful characterization of the GaN:ZnO solid solution nanorods indicated that the nitridation temperature is an important parameter affecting the photocatalytic performance, which is related to the specific surface area and the absorbable visible-light wavelength range. Finally, the mechanism of the GaN:ZnO solid solution nanorods was also investigated. The proposed synthesis strategy paves a new way to realize excellent activity and recyclability of GaN:ZnO solid solution nanorod photocatalysts for hydrogen generation.

Nanotip Formation from Liquid Metals for Soft Electronic Junctions

Liquid metals and alloys with high-aspect-ratio nanodimensional features are highly sought-after for emerging electronic applications. However, high surface tension, water-like fluidity, and the existence of self-limiting oxides confer specific peculiarities to their characteristics. Here, we introduce a high accuracy nanometric three-dimensional pulling and stretching method to fabricate liquid-metal-based nanotips from room- or near-room-temperature gallium-based alloys. The pulling rate and step size were controlled with a resolution of up to 10 nm and yielded different nanotip morphologies and lengths as a function of the base liquid metal alloy composition and the pulling parameters. The obtained nanotips presented high aspect ratios over lengths of a few microns and apexes between 10 and 100 nm. The liquid metal alloys were found confined within nanotips with about 10 nm apexes when vertically pulled at 100 nm/s. An amorphous gallium oxide skin was shown to cover the surface of the nanotips, while the liquid core was composed of the initial liquid metal alloys. The electrical contact established at the nanotips was characterized under dynamic conditions. The liquid metal nanotips showed an Ohmic resistance when a continuous liquid metal channel was formed, and a controllable semiconductor state corresponding to a heterojunction formed at the junction between the liquid metal phase and the gallium oxide semiconductor skin. The variable threshold voltages of the heterojunction were controlled via stretching of the nanotips with a 10 nm step resolution. The liquid metal nanotips were also used for establishing soft electronic junctions. This novel method of liquid metal nanotip fabrication with Ohmic and semiconducting behaviors will lead to exciting avenues for developing electronic and sensing devices.

Nanostructure Engineering and Modulation of (Oxy)Nitrides for Application in Visible-Light-Driven Water Splitting

(Oxy)nitride-based nanophotocatalysts have been extensively investigated for solar-to-chemical conversion, and not only allow wide spectral utilization to achieve high theoretical energy conversion efficiency but also exhibit suitable conduction and valence band positions for robust reduction and oxidation of water. During the past decades, a few reviews on the research progress in designing and synthesizing new visible-light-responsive semiconductors for various applications in solar-to-chemical conversion have been published. However, those on the effects of their bulk and composite (surface/interface) nanostructures on basic processes as well as solar water splitting performances to produce hydrogen are still limited. In this review, a brief introduction on the relationship between the nanostructure photocatalytic properties is included. Three main processes of solar water splitting are involved, allowing the elucidation of the correlation with the nanostructural properties of the photocatalyst such as surface/interface, size, morphology, and bulk structure. Subsequently, the development of methodologies and strategies for modulating the bulk and composite structures to improve the efficiencies of the basic processes, particularly charge separation, is summarized in detail. Finally, the prospects of (oxy)nitride-based photocatalysts such as controlled synthesis, modulation of 1D/2D morphology, exposed facet regulation, heterostructure formation, theoretical simulation, and time- and space-resolved spectroscopy are discussed.

NH4F-Induced Morphology Control of CoP Nanostructures to Enhance the Hydrogen Evolution Reaction

Developing non-noble metal catalysts with superior catalytic activity and excellent durability is critically essential to promote electrochemical water splitting for hydrogen production. Morphology control as a promising and effective strategy is widely implemented to change the surface atomic coordination and thus enhance the intrinsic catalytic performance of current electrocatalysts. Herein, a series of cobalt phosphide (CoP) electrocatalysts with tunable morphologies of nanosheets, nanowires, nanorods, and nanoblocks have been prepared for the enhanced hydrogen evolution reaction (HER) by only adjusting the amount of ammonium fluoride (NH₄F) in the hydrothermal process. Benefiting from the large active area, high surface activity, and favorable ion and gas diffusion channels, the clustered CoP nanorods obtained at a concentration of 0.15 M NH₄F show the best HER performance with only an overpotential of 71 mV at a current density of 10 mA cm^-2 and a low Tafel slope of 60.75 mV dec^-1 in 1 M KOH. After 3000 CV cycles and 24 h durability tests, there is only a very slight degradation of performance owing to its outstanding stability and robust substrate adhesion.

Versatile precursor-dependent copper sulfide nanoparticles as a multifunctional catalyst for the photocatalytic removal of water pollutants and the synthesis of aromatic aldehydes and NH-triazoles

A series of copper sulfide (CS) nanoparticles (NPs) were synthesized just by varying the amount of the sulfur precursor and have been explored for the first time as a three-way heterogeneous catalyst in the photocatalytic oxidation of a number of aromatic alcohols, photocatalytic degradation and the reduction of water pollutants, and the facile synthesis of pharmaceutically important moiety 4-aryl-NH-1,2,3-triazoles. The green and novel protocol was successfully developed for the synthesis of covellite (CuS, Cu2+) and the covellite-villamaninite (CuS-CuS2) (copper in Cu2+, Cu1+) phases of copper sulfide, employing EDTA both as the chelating and capping agent via a simple precipitation method at room temperature using water as the solvent. A blue shift in the absorption spectra and band gap in the range of 2.02-2.07 eV prompted the investigation of the as-synthesized CS nanoparticles as the photocatalyst under visible light irradiation. In the absence of any oxidizing or reducing agent, covellite CuS nanoparticles showed the highest photocatalytic efficiency for the degradation of methylene blue (MB) and the reduction of carcinogenic and mutagenic Cr(vi) to non-toxic Cr(iii). Interestingly, the mixed phase of CS (CuS-CuS2), where Cu is present in both +1 and +2 oxidation states, was found to be the most efficient catalyst compared to CuS toward the visible light-mediated selective oxidation of various benzyl alcohols to their corresponding aldehydes. However, in the synthesis of substituted NH-1,2,3-triazoles, single-phase CS nanoparticles (i.e., CuS) provided the best catalytic result. This significant outcome certainly opens up the scope for realizing the present demand of low-cost multifunctional semiconductor nano-materials, which will have a huge impact on the economy and environment when they show more than two potential applications.

CuS/KTa0.75Nb0.25O3 nanocomposite utilizing solar and mechanical energy for catalytic N2 fixation

This work synthesized a novel CuS/KTa_0.75Nb_0.25O₃ (KTN) heterojunction composite and firstly applied it in photocatalytic and piezocatalytic reduction of N₂ to NH₃. XRD, Raman, XPS, SEM, and TEM analyses indicate that CuS nanoparticles closely adhered to the surface of KTN nanorods, which facilitates the migration of electrons between the two semiconductors. Mott-Schottky and valence band XPS analysis shows that KNbO₃ shows a higher conduction band than CuS, indicating that CuS mainly acts as electron trappers to capture the photogenerated electrons from KTN. Because of the great enhanced spatial separation of photogenerated charge carriers, the CuS/KTN presents much higher performance than pure KNT, which is further confirmed by ¹H NMR analysis of the reaction solution. An interesting finding is that synthesized CuS/KTN not only performs well under light irradiation but also can work in an ultrasonic bath, indicating its great potential in photo/piezocatalytic conversion of N₂ to NH₃. The optimal 10 %CuS/KTN shows an NH₃ production rate of 36.2 μmol L^-1 g^-1 h^-1 under ultrasonic vibration, which reaches 7.4 times that of KTN. The electrons generated by KTN through the piezoelectric effect can be captured by CuS, which endows the electrons a longer life to participate in the reaction, thereby improving the catalytic reaction performance.

Interface Engineering of a 2D-C3N4/NiFe-LDH Heterostructure for Highly Efficient Photocatalytic Hydrogen Evolution

Photocatalytic water splitting offers an economic and sustainable pathway for producing hydrogen as a zero-emission fuel, but it still suffers from low efficiencies limited by visible-light absorption capacity and charge separation kinetics. Herein, we report an interface-engineered 2D-C₃N₄/NiFe layered double hydroxide (CN/LDH) heterostructure that shows highly enhanced photocatalytic hydrogen evolution reaction (HER) rate with excellent long-term stability. The morphology and band gap structure of NiFe-LDH are precisely regulated by employing NH₄F as a structure-directing agent, which enables a fine interfacial tuning via coupling with 2D-C₃N₄. The formation of a type II interface in CN/LDH enlarges the active surface area and promotes the charge separation efficiency, leading to an HER rate of 3087 μmol g^-1 h^-1, which is 14 times higher than that of 2D-C₃N₄. This study highlights a rational interface engineering strategy for the formation of a heterostructure with a proper hole transport co-catalyst for designing effective water-splitting photocatalysts.

Zn-rich (GaN)1−x(ZnO)x: a biomedical friend?

The synthesis of (GaN)_1−x(ZnO)_x with the assistance of high-gravity using a green approach for the first time, with the application of delivering pCRISPR.