Polyethylene glycol assisted one-pot hydrothermal synthesis of NiWO4/WO3 heterojunction for direct Methanol fuel cells

A novel p-n Mn0.2Cd0.8S/NiWO4 heterojunction for highly efficient photocatalytic H2 production

Constructing a p-n heterojunction has been regarded as an effective way to restrain charge recombination and boost photocatalytic H2 production activity. Herein, a novel Mn0.2Cd0.8S/NiWO4 composite was fabricated by a hydrothermal process and which exhibited enhanced H2 production activity and excellent photostability. Particularly, the composite with 30 wt% of NiWO4 achieved the optimal H2 production rate of 17.76 mmol g-1 h-1, which was 2.9 times higher than that of Mn0.2Cd0.8S. The increased H2 production property was mainly due to the p-n heterojunction between Mn0.2Cd0.8S and NiWO4, which provided an efficient path for charge transfer and inhibited the photocorrosion of Mn0.2Cd0.8S. This work can offer technical support for the design and development of p-n heterojunctions that can be applied for photocatalytic H2 production.

High quality electrocatalyst by Pd-Pt alloys nanoparticles uniformly distributed on polyaniline/carbon nanotubes for effective methanol oxidation

In the present work, Pd-Pt nanoparticle/polyaniline/carbon nanotube (NP/PANI/CNT) composites, synthesized through the uniform distribution of Pd-Pt NPs, whose single size was controlled to 2-4 nm by citric acid, on a PANI/CNT compound, served as the electrode catalysts for effective methanol oxidation. The structural characteristics were identified by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy, and revealed that the Pt₆₅Pd₃₅ NP/PANI/CNT composite displayed superior electrocatalytic oxidation performance and vitality in various Pd-Pt NPs. The results indicated that as an excellent anode catalyst the complex would have application prospects for effective methanol oxidation.

Synthesis of Graphene Oxide Interspersed in Hexagonal WO3 Nanorods for High-Efficiency Visible-Light Driven Photocatalysis and NH3 Gas Sensing

WO₃ nanorods and GO (at 1 wt% loading) doped WO₃ were synthesized using a template free deposition-hydrothermal route and thoroughly characterized by various techniques including XRD, FTIR, Raman, TEM-SAED, PL, UV-Vis, XPS, and N₂ adsorption. The nano-materials performance was investigated toward photocatalytic degradation of methylene blue dye (20 ppm) under visible light illumination (160 W, λ> 420) and gas sensing ability for ammonia gas (10–100 ppm) at 200°C. HRTEM investigation of the 1%GO.WO₃ composite revealed WO₃ nanorods of a major d-spacing value of 0.16 nm indexed to the crystal plane (221). That relevant plane was absent in pure WO₃ establishing the intercalation with GO. The MB degradation activity was considerably enhanced over the 1%GO.WO₃ catalyst with a rate constant of 0.0154 min⁻¹ exceeding that of WO₃ by 15 times. The reaction mechanism was justified dependent on electrons, holes and •OH reactive species as determined via scavenger examination tests and characterization techniques. The drop in both band gap (2.49 eV) and PL intensity was the main reason responsible for enhancing the photo-degradation activity of the 1%GO.WO₃ catalyst. The later catalyst initiated the two electron O₂ reduction forming H₂O₂, that contributed in the photoactivity improvement via forming •OH moieties. The hexagonal structure of 1%GO.WO₃ showed a better gas sensing performance for ammonia gas at 100 ppm (R_a-R_g/R_g = 17.6) exceeding that of pure WO₃ nanorods (1.27). The superiority of the gas-sensing property of the 1%GO.WO₃ catalyst was mainly ascribed to the high dispersity of GO onto WO₃ surfaces by which different carbon species served as mediators to hinder the recombination rate of photo-generated electron-hole pairs and therefore facilitated the electron transition. The dominancy of the lattice plane (221) in 1%GO.WO₃ formed between GO and WO₃ improved the electron transport in the gas-sensing process.

Accelerated charge transfer via a nickel tungstate modulated cadmium sulfide p–n heterojunction for photocatalytic hydrogen evolution

Improving the efficiency of charge separation is an important aspect in photocatalysis.