Iron Sulfide Materials: Catalysts for Electrochemical Hydrogen Evolution

Synthesis of Sb2S3 nanosphere layer by chemical bath deposition for the photocatalytic degradation of methylene blue dye

An antimony tri-sulfide Sb₂S₃ nanosphere photocatalyst was effectively deposited utilizing sodium thiosulfate and antimony chloride as the starting precursors in a chemical bath deposition process. This approach is appropriate for the large-area depositions of Sb₂S₃ at low deposition temperatures without the sulfurization process since it is based on the hydrolytic decomposition of starting compounds in aqueous solution. X-ray diffraction patterns and Raman spectroscopy analysis revealed the formation of amorphous Sb₂S₃ layers. The scanning electron microscopy images revealed that the deposited Sb₂S₃ has integrated small nanospheres into sub-microspheres with a significant surface area, resulting in increased photocatalytic activity. The optical direct bandgap of the Sb₂S₃ layer was estimated to be about 2.53 eV, making amorphous Sb₂S₃ appropriate for the photodegradation of organic pollutants in the presence of solar light. The possibility of using the prepared Sb₂S₃ layer in the photodegradation of methylene blue aqueous solutions was investigated. The degradation of methylene blue dye was performed to evaluate the photocatalytic property of Sb₂S₃ under visible light. The amorphous Sb₂S₃ exhibited photocatalytic activity for the decolorization of methylene blue solution under visible light. The mechanism for the photocatalytic degradation of methylene blue has been proposed. Our results suggest that the amorphous Sb₂S₃ nanospheres are valuable material for addressing environmental remediation issues.

Metal Catalysis Acting on Nitriles in Early Earth Hydrothermal Systems

Hydrothermal systems are areas in which heated fluids and organic molecules rush through basaltic material rich in metals and minerals. By studying malononitrile and acetonitrile, we examine the effects of metal and mineral nanoparticles on nitrile compounds in anoxic, hydrothermal conditions representing a prebiotic environment of early Earth. Polymerization, reduction, cyclization, and a phenomenon colloquially known as 'chemical gardening' (structure building via reprecipitation of metal compounds or complexing with organics) are all potential outcomes with the addition of metals and minerals. Reduction occurs with the addition of rhodium (Rh) or iron (II) sulfide (FeS), with positive identification of ethanol and ethylamine forming from acetonitrile reduction. We find that polymerization and insoluble product formation were associated with oxide minerals, metallic nickel (Ni), and metallic cobalt (Co) acting as catalysts. Oxide minerals strongly promoted polymerization into insoluble, tar-like products of nitriles. FeS, iron-nickel alloy (FeNi), and rhodium are unique cases that appear to act as reagents by actively participating in chemical gardening without returning to their initial state. Further, FeS tentatively had a phase change into the mineral parabutlerite. This research aims to identify metals and metal minerals that could best serve nitrile catalysis and reactions on early Earth.

Microwave-Assisted Fabrication of High Energy Density Binary Metal Sulfides for Enhanced Performance in Battery Applications

Nanomaterials have found use in a number of relevant energy applications. In particular, nanoscale motifs of binary metal sulfides can function as conversion materials, similar to that of analogous metal oxides, nitrides, or phosphides, and are characterized by their high theoretical capacity and correspondingly low cost. This review focuses on structure-composition-property relationships of specific relevance to battery applications, emanating from systematic attempts to either (1) vary and alter the dimension of nanoscale architectures or (2) introduce conductive carbon-based entities, such as carbon nanotubes and graphene-derived species. In this study, we will primarily concern ourselves with probing metal sulfide nanostructures generated by a microwave-mediated synthetic approach, which we have explored extensively in recent years. This particular fabrication protocol represents a relatively facile, flexible, and effective means with which to simultaneously control both chemical composition and physical morphology within these systems to tailor them for energy storage applications.

A facile chemical synthesis of nanoflake NiS2 layers and their photocatalytic activity

A single-phase and crystalline NiS₂ nanoflake layer was produced by a facile and novel approach consisting of a two-step growth process. First, a Ni(OH)₂ layer was synthesized by a chemical bath deposition approach using a nickel precursor and ammonia as the starting solution. In a second step, the obtained Ni(OH)₂ layer was transformed into a NiS₂ layer by a sulfurization process at 450 °C for 1 h. The XRD analysis showed a single-phase NiS₂ layer with no additional peaks related to any secondary phases. Raman and X-ray photoelectron spectroscopy further confirmed the formation of a single-phase NiS₂ layer. SEM revealed that the NiS₂ layer consisted of overlapping nanoflakes. The optical bandgap of the NiS₂ layer was evaluated with the Kubelka-Munk function from the diffuse reflectance spectrum (DRS) and was estimated to be around 1.19 eV, making NiS₂ suitable for the photodegradation of organic pollutants under solar light. The NiS₂ nanoflake layer showed photocatalytic activity for the degradation of phenol under solar irradiation at natural pH 6. The NiS₂ nanoflake layer exhibited good solar light photocatalytic activity in the photodegradation of phenol as a model organic pollutant.

Accelerated optimization of pure metal and ligand compositions for light-driven hydrogen production

Data-driven optimization of hydrogen production.

Synthetic Organic Design for Solar Fuel Systems

From the understanding of biological processes and metalloenzymes to the development of inorganic catalysts, electro- and photocatalytic systems for fuel generation have evolved considerably during the last decades. Recently, organic and hybrid organic systems have emerged to challenge the classical inorganic structures through their enormous chemical diversity and modularity that led earlier to their success in organic (opto)electronics. This Minireview describes recent advances in the design of synthetic organic architectures and promising strategies toward (solar) fuel synthesis, highlighting progress on materials from organic ligands and chromophores to conjugated polymers and covalent organic frameworks.

Nano-synthesis of solid acid catalysts from waste-iron-filling for biodiesel production using high free fatty acid waste cooking oil

Waste-iron-filling (WIF) served as a precursor to synthesize α-[Formula: see text] through the co-precipitation process. The α-[Formula: see text] was converted to solid acid catalysts of RBC500, RBC700, and RBC900 by calcination with temperatures of 500, 700 and 900 °C respectively and afterwards sulfonated. Among the various techniques employed to characterize the catalysts is Fourier transforms infrared spectrometer (FT-IR), X-ray diffraction (XRD and Scanning electron microscopy (SEM). Performance of the catalysts was also investigated for biodiesel production using waste cooking oil (WCO) of 6.1% free fatty acid. The XRD reveals that each of the catalysts composed of Al-[Formula: see text]. While the FT-IR confirmed acid loading by the presence of [Formula: see text] groups. The RBC500, RBC700, and RBC900 possessed suitable morphology with an average particle size of 259.6, 169.5 and 95.62 nm respectively. The RBC500, RBC700, and RBC900 achieved biodiesel yield of 87, 90 and 92% respectively, at the process conditions of 3 h reaction time, 12:1 MeOH: WCO molar ratio, 6 wt% catalyst loading and 80 °C temperature. The catalysts showed the effectiveness and relative stability for WCO trans-esterification over 3 cycles. The novelty, therefore, is the synthesis of nano-solid acid catalyst from WIF, which is cheaper and could serve as an alternative source for the ferric compound.

A multifunctional Ni-doped iron pyrite/reduced graphene oxide composite as an efficient counter electrode for DSSCs and as a non-enzymatic hydrogen peroxide electrochemical sensor

Nickel-doped FeS₂/rGO composites were synthesized as multifunctional materials via a facile hydrothermal method. The synthesized materials were characterized with XRD, FESEM, XPS, and TEM-SAED for structural, morphological and chemical studies. To study their electrochemical properties, all the synthesized composites were subjected to cyclic voltammetry tests. The optimum composite revealed high catalytic activity with high peak current density, limiting current, and efficiency of 7.60% for DSSC, which surpassed that of a platinum-based counter electrode (6.69%). The efficiency of the DSSC was significantly supported by interfacial studies and electron lifetime studies, and it exhibited lower charge transfer resistance and higher electron lifetime, respectively. Moreover, the fabricated DSSCs with high efficiency were subjected to transient photo-response studies and showed a stable current response with multiple photo-ON and OFF cycles for a period of 600 s. To broaden the application of the synthesized material, it was used as an electrochemical sensor for the efficient sensing of hydrogen peroxide (H₂O₂). The sensing electrode was modified with the optimum Ni-doped FeS₂/rGO composite, and voltammetric detection was carried out in the hydrogen peroxide concentration range of 4-100 μM. Thus, the synthesized material can be applied in DSSCs and as an electrochemical H₂O₂ sensor.