Efficient electrochemical hydrogen evolution activity of nanostructured Ag3PO4/MoS2 heterogeneous composite catalyst

Hydrogen (H2) generation by electrochemical water splitting is a key technique for sustainable energy applications. Two-dimensional (2D) transition-metal dichalcogenide (MoS2) and silver phosphate (Ag3PO4) possess excellent electrochemical hydrogen evolution reaction (HER) properties when they are combined together as a composite rather than individuals. Reports examining the HER activity by using Ag3PO4, especially, in combination with the 2D layered MoS2 are limited in literature. The weight fraction of MoS2 in Ag3PO4 is optimized for 1, 3, and 5 wt%. The Ag3PO4/1 wt % MoS2 combination exhibits enhanced HER activity with least overpotential of 235 mV among the other samples in the acidic medium. The synergistic effect of optimal nano-scale 2D layered MoS2 structure and Ag3PO4 is essential for creating higher electrochemical active surface area of 217 mF/cm2, and hence this leads to faster reaction kinetics in the HER. This work suggests the advantages of Ag3PO4/1 wt % MoS2 heterogeneous composite catalyst for electrochemical analysis and HER indicating lower resistivity and low Tafel slope value (179 mV/dec) among the prepared catalysts making it a promising candidate for its use in practical energy applications.

Assessment of Performance of Photocatalytic Nanostructured Materials with Varied Morphology Based on Reaction Conditions

Synthesis of nanomaterials with specific morphology is an essential aspect for the optimisation of its properties and applications. The application of nanomaterials is being discussed in a wide range of areas, one of which is directly relevant to the environment through photocatalysis. To produce an effective photocatalyst for environmental applications, morphology plays an important role as it affects the surface area, interfaces, crystal facets and active sites, which ultimately affects efficiency. The method of synthesis and synthesis temperature can be the basic considerations for the evaluation of a particular nanomaterial. In this study, we have considered the aspects of morphology with a basic understanding and analyzed them in terms of nanomaterial efficacy in photocatalysis. Different morphologies of specific nanomaterials such as titanium dioxide, zinc oxide, silver phosphate, cadmium sulphide and zinc titanate have been discussed to come to reasonable conclusions. Morphologies such as nanorods, nanoflower, nanospindles, nanosheets, nanospheres and nanoparticles were compared within and outside the domain of given nanomaterials. The different synthesis strategies adopted for a specific morphology have been compared with the photocatalytic performance. It has been observed that nanomaterials with similar band gaps show different performances, which can be linked with the reaction conditions and their nanomorphology as well. Materials with similar morphological structures show different photocatalytic performances. TiO₂ nanorods appear to have the best features of efficient photocatalyst, while the nanoflowers show very low efficiency. For CdS, the nanoflower is the best morphology for photocatalysis. It appears that high surface area is the key apart from the morphology, which controls the efficiency. The overall understanding by analyzing all the available information has enumerated a path to select an effective photocatalyst amongst the several nanomaterials available. Such an analysis and comparison is unique and has provided a handle to select the effective morphology of nanomaterials for photocatalytic applications.

Photocatalytic activity of Pr-modified TiO2 for the degradation of bisphenol A

Praseodymium doped TiO2 nanoparticles were successfully prepared by the sol–gel method and characterized by X-ray powder diffraction, N2 adsorption–desorption isotherm, and UV–vis spectroscopy. The effects of the dopant on the crystallite size, specific surface area, average pore diameter, pore volume, and bandgap energy were investigated. The photocatalytic activity of the catalysts was evaluated by bisphenol A degradation and mineralization, which is a representative endocrine disruptor. Furthermore, under visible light irradiation the Pr-modified TiO2 photocatalysts exhibited higher photocatalytic efficiency than unmodified TiO2. When praseodymium was loaded (1.0–5.0%) onto the surface of TiO2, the rates of degradation and mineralization were increased 3–5 times.

Photodegradation of ethyl paraben using simulated solar radiation and Ag3PO4 photocatalyst

In this work, the solar light-induced photocatalytic degradation of ethyl paraben (EP), a representative of the parabens family, was studied using silver orthophosphate, a relatively new photocatalytic material. The catalyst was synthesized by a precipitation method and had a primary crystallite size of ca 70nm, specific surface area of 1.4m²/g and a bandgap of 2.4eV. A factorial design methodology was implemented to evaluate the importance of EP concentration (500-1500μg/L), catalyst concentration (100-500mg/L), reaction time (4-30min), water matrix (pure water or 10mg/L humic acid) and initial solution pH (3-9) on EP removal. All individual effects but solution pH were statistically significant and so were the second-order interactions of EP concentration with reaction time or catalyst concentration. The water matrix effect was negative (all other effects were positive) signifying the role of humic acid as scavenger of the oxidant species. Liquid chromatography-time of flight mass spectrometry revealed the formation of methyl paraben, 4-hydroxybenzoic acid, benzoic acid and phenol as primary transformation by-products; these are formed through dealkylation and decarboxylation reactions initiated primarily by the photogenerated holes. Estrogenicity assays showed that methyl paraben was more estrogenic than EP; however, parabens are slightly estrogenic compared to 17β-estradiol.

Copper hydroxyl sulfate as a heterogeneous catalyst for the catalytic wet peroxide oxidation of phenol

Copper hydroxyl sulfates Cu₄(OH)₆SO₄-A and Cu₄(OH)₆SO₄-B were successfully synthesized by a simple hydrothermal method and applied as heterogeneous catalysts to degrade phenol wastewater in the presence of hydrogen peroxide (H₂O₂).

Self-assembled macro porous ZnS–graphene aerogels for photocatalytic degradation of contaminants in water

This work demonstrates the facile green synthesis of ZnS–graphene aerogels with superior photocatalytic performance.