Carbon Dioxide Photoreduction on the Bi2S3/MoS2 Catalyst

Role of Facets and Morphologies of Different Bismuth-Based Materials for CO2 Reduction to Fuels

Carbon dioxide (CO2) emission has been a global concern over the past few decades due to the increase in the demand of energy, a major source of which is fossil fuels. To mitigate the emission issues, as well as to find a solution for the energy needs, an ample load of research has been carried out over the past few years in CO2 reduction by catalysis. Bismuth, being an active catalyst both photocatalytically and electrocatalytically, is an interesting material that can be formed into oxides, sulphides, oxyhalides, etc. Numerous works have been published based on bismuth-based materials as active catalysts for the reduction of CO2. However, a proper understanding of the behavior of the active facets and the dependence of morphology of the different bismuth-based catalysts is an interesting notion. In this review, various bismuth-based materials will be discussed regarding their activity and charge transfer properties, based on the active facets present in them. With regard to the available literature, a summarization, including photocatalysis, electrocatalysis as well as photoelectrocatalysis, will be detailed, considering various materials with different facets and morphologies. Product selectivity, varying on morphological difference, will also be realized photoelectrochemically.

Ultrasensitive and reversible NO2 gas sensor based on SnS2/TiO2 heterostructures for room temperature applications

Nitrogen dioxide (NO2) is one of the toxic gases produced by chemical industries, power plants, and vehicles. In this work, we demonstrate an inexpensive sensing platform for NO2 detection at room temperature (RT-32 °C) based on a charge transfer mechanism. Three-dimensional hierarchical SnS2 and SnS2/mesoporous TiO2 nanocomposites were synthesized via the solvothermal method. SnS2/20 wt% mesoporous TiO2 nanocomposites sample showed 245.4% enhanced response compared to pristine SnS2. The fabricated device exhibits excellent selectivity among all other interfering gases with one-month stability. The rapid response and enhanced response achieved were obtained for the minimum concentration of 2 ppm NO2. The formation of heterojunction between SnS2 and mesoporous TiO2 has a synergetic effect, providing more active sites and porous structures for the detection of NO2 gas molecules.

MoS2-Based Nanocomposites for Photocatalytic Hydrogen Evolution and Carbon Dioxide Reduction

Photocatalysis is a facile and sustainable approach for energy conversion and environmental remediation by generating solar fuels from water splitting. Due to their two-dimensional (2D) layered structure and excellent physicochemical properties, molybdenum disulfide (MoS₂) has been effectively utilized in photocatalytic H₂ evolution reaction (HER) and CO₂ reduction. The photocatalytic efficiency of MoS₂ greatly depends on the active edge sites present in their layered structure. Modifications like reducing the layer numbers, creating defective structures, and adopting different morphologies produce more unsaturated S atoms as active edge sites. Hence, MoS₂ acts as a cocatalyst in nanocomposites/heterojunctions to facilitate the photogenerated electron transfer. This review highlights the role of MoS₂ as a cocatalyst for nanocomposites in H₂ evolution reaction and CO₂ reduction. The H₂ evolution activity has been described comprehensively as binary (with metal oxide, carbonaceous materials, metal sulfides, and metal-organic frameworks) and ternary composites of MoS₂. Photocatalytic CO₂ reduction is a more complex and challenging process that demands an efficient light-responsive semiconductor catalyst to tackle the thermodynamic and kinetic factors. Photocatalytic reduction of CO₂ using MoS₂ is an emerging topic and would be a cost-effective substitute for noble catalysts. Herein, we also exclusively envisioned the possibility of layered MoS₂ and its composites in this area. This review is expected to furnish an understanding of the diverse roles of MoS₂ in solar fuel generation, thus endorsing an interest in utilizing this unique layered structure to create nanostructures for future energy applications.

Recent Advances in Molybdenum Disulfide and Its Nanocomposites for Energy Applications: Challenges and Development

Energy storage and conversion are critical components of modern energy systems, enabling the integration of renewable energy sources and the optimization of energy use. These technologies play a key role in reducing greenhouse gas emissions and promoting sustainable development. Supercapacitors play a vital role in the development of energy storage systems due to their high power density, long life cycles, high stability, low manufacturing cost, fast charging-discharging capability and eco-friendly. Molybdenum disulfide (MoS₂) has emerged as a promising material for supercapacitor electrodes due to its high surface area, excellent electrical conductivity, and good stability. Its unique layered structure also allows for efficient ion transport and storage, making it a potential candidate for high-performance energy storage devices. Additionally, research efforts have focused on improving synthesis methods and developing novel device architectures to enhance the performance of MoS₂-based devices. This review article on MoS₂ and MoS₂-based nanocomposites provides a comprehensive overview of the recent advancements in the synthesis, properties, and applications of MoS₂ and its nanocomposites in the field of supercapacitors. This article also highlights the challenges and future directions in this rapidly growing field.

2D/1D MoS2 /TiO2 Heterostructure Photocatalyst with a Switchable CO2 Reduction Product

Regulating the transfer pathway of charge carriers in heterostructure photocatalysts is of great importance for selective CO₂ photoreduction. Herein, the charge transfer pathway and in turn the redox potential succeeded to regulate in 2D MoS₂ /1D TiO₂ heterostructure by varying the light wavelength range. Several in situ measurements and experiments confirm that charge transfer follows either an S-scheme mechanism under simulated solar irradiation or a heterojunction approach under visible light illumination, elucidating the switchable property of the MoS₂ /TiO₂ heterostructure. Replacing the simulated sunlight irradiation with the visible light illumination switches the photocatalytic CO₂ reduction product from CO to CH_4. ¹³ CO₂ isotope labeling confirms that CO₂ is the source of carbon for CH₄ and CO products. The photoelectrochemical H₂ generation further supports the switching property of MoS₂ /TiO₂ . Unlike previous studies, density functional theory calculations are used to investigate the band structure of Van der Waals MoS₂ /TiO₂ S scheme after contact, allowing to propose accurate charge transfer pathways, in which the theoretical results are well matched with the experimental results. This work opens the opportunity to develop photocatalysts with switchable charge transport and tunable redox potential for selective artificial photosynthesis.

Construction of a flower-like SnS2/SnO2 junction for efficient photocatalytic CO2 reduction

Photoreduction of CO2 to value-added chemicals and fuels is an attractive solution to alleviate environmental problems and energy crisis at the same time. However, engineering efficient photocatalysts with high activity and product selectivity is still challenging. Herein, we achieved three-dimensional (3D) spatial configuration design at micro-scale and heterogeneous interface construction at nano-scale on a SnS2/SnO2 composite, which featured hierarchical flower-like morphology consisted of nanosheets and type-II semiconductor structure. It behaved excellent selectivity and impressive photocatalytic CO2-to-CO performance with a yielding rate of 60.85 μmol g-1h-1, roughly 3 times higher than that of SnS2 and was in the front rank of this kind catalysts under 300 W Xe lamp illumination without using any sensitizers or noble metals. The enhanced catalytic capability could be attributed to the elaborately built structure with suitable energetic position that afforded effective separation and migration of photo-generated electron/hole pairs as well as enhanced light caption and absorption. Meanwhile, main reactive intermediates (e.g., CO2- and *COOH) were captured by in-situ Fourier transform infrared spectroscopy (FTIR), suggesting a fluent catalytic pathway on the SnS2/SnO2 platform. This work provides a new scheme to build advanced catalysts based on multiscale design and rational phase assembling.

Fiber-like ZnO with highly dispersed Pt nanoparticles for enhanced photocatalytic CO2 reduction

Utilizing solar energy to convert carbon dioxide (CO₂) into chemical fuels could simultaneously mitigate the greenhouse effect and fossil fuel crisis. Herein, a heterogeneous photocatalyst of ZnO nanofiber deposited by Pt nanoparticles was successfully synthesized toward photocatalytic CO₂ reduction via radio-frequency thermal plasma and photo-deposition method. The Pt nanoparticles were introduced on the surface of ZnO nanofibers to broaden the light absorption and utilization, increase the additional reaction active sites and facilitate the separation of photo-generated electron/hole pairs. Combined with the natural advantages of short transfer path of charge carriers and self-support effecting in humid reaction environment for nanofibers, the Pt/ZnO hetero-junction nanocomposites displayed superior photocatalytic activity for CO₂ reduction with respect to bare ZnO nanofibers, affording a CO-production rate as high as 45.76 μmol g^-1 h^-1 under 300 W Xe lamp irradiation within a gas-solid reaction system. Furthermore, in-suit Fourier transform infrared (FTIR) spectra were applied to unveil the details during photocatalytic CO₂ reduction. This work presents a hetero-junction nanocomposite photocatalyst based on eco-friendly semiconductor and metal materials.

Carbon dioxide photoreduction in prebiotic environments

The reduction of carbon dioxide is one of the hottest topics due to the concern of global warming. Carbon dioxide reduction is also an essential step for life's origins as photoautotrophs arose soon after Earth formation. Both the topics are of high general interest, and possibly, there could be a fruitful cross-fertilization of the two fields. Herein, we selected and collected papers related to photoreduction of carbon dioxide using compounds easily available on the Earth and considered of prebiotic relevance. This work might be useful also to scientists interested in carbon dioxide photoreduction and/or to have an overview of the techniques available.

1D/2D constructed Bi2S3/Bi2O2CO3 direct Z-Scheme heterojunction: A versatile photocatalytic material for boosted photodegradation, photoreduction and photoelectrochemical detection of water-based contaminants

In this work, two-dimensional Bi₂O₂CO₃ disk is synthesized, followed by the growth of Bi₂S₃ over Bi₂O₂CO₃ via topotactic transformation by controlling the amount of thiourea under hydrothermal conditions. The synthesized composite catalyst is investigated for photocatalytic oxidation and reduction of tetracycline hydrochloride and hexavalent chromium under visible light irradiation. High interfacial contact between the Bi₂O₂CO₃ disk0 and Bi₂S₃ fiber is confirmed via high-resolution microscopic imaging. Enhanced light absorption and increased charge carrier separation is observed after the formation of the Bi₂S₃/Bi₂O₂CO₃ composite. The Bi₂S₃/Bi₂O₂CO₃ composite grown using 1 mmol of thiourea shows approximately 98% degradation of tetracycline hydrochloride after 120 min and 99% Cr(VI) reduction after 90 min of photochemical reaction under visible light irradiation. The charge separation is due to the formed internal electric field at the interface, which upon light irradiation follows a z-scheme charge transfer hindering the recombination at the Bi₂S₃ and Bi₂O₂CO₃ interface, thereby contributing efficiently to the photochemical process. In addition, the mechanism of the photochemical reaction for the degradation of pollutants is supported using quencher and probe experiments. Furthermore, photoelectrochemical detection of antibiotic in aqueous solution is conducted to understand the sensing feasibility of the synthesized system.

A Review on MoS2 Energy Applications: Recent Developments and Challenges

Molybdenum disulfide (MoS2) is a promising transition metal dichalcogenide (TMD) that has exceptional electronic, magnetic, optical, and mechanical properties. It can be semiconducting, superconducting, or an insulator according to its polymorph. Its bandgap structure changes from indirect to direct when moving towards its nanostructures, which opens a door to bandgap engineering for MoS2. Its supercapacitive and catalytic activity was recently noticed and studied, in order to include this material in a wide range of energy applications. In this work, we present MoS2 as a future material for energy storage and generation applications, especially solar cells, which are a cornerstone for a clean and abundant source of energy. Its role in water splitting reactions can be utilized for energy generation (hydrogen evolution) and water treatment at the same time. Although MoS2 seems to be a breakthrough in the energy field, it still faces some challenges regarding its structure stability, production scalability, and manufacturing costs.

High Loading of Transition Metal Single Atoms on Chalcogenide Catalysts

Transition metal doped chalcogenides are one of the most important classes of catalysts that have been attracting increasing attention for petrochemical and energy related chemical transformations due to their unique physiochemical properties. For practical applications, achieving maximum atom utilization by homogeneous dispersion of metals on the surface of chalcogenides is essential. Herein, we report a detailed study of a deposition method using thiourea coordinated transition metal complexes. This method allows the preparation of a library of a wide range of single atoms including both noble and non-noble transition metals (Fe, Co, Ni, Cu, Pt, Pd, Ru) with a metal loading as high as 10 wt % on various ultrathin 2D chalcogenides (MoS₂, MoSe₂, WS₂ and WSe₂). As demonstrated by the state-of-the-art characterization, the doped single transition metal atoms interact strongly with surface anions and anion vacancies in the exfoliated 2D materials, leading to high metal dispersion in the absence of agglomeration. Taking Fe on MoS₂ as a benchmark, it has been found that Fe is atomically dispersed until 10 wt %, and beyond this loading, formation of coplanar Fe clusters is evident. Atomic Fe, with a high electron density at its conduction band, exhibits a superior intrinsic activity and stability in CO₂ hydrogenation to CO per Fe compared to corresponding surface Fe clusters and other Fe catalysts reported for reverse water-gas-shift reactions.

Powering the next industrial revolution: transitioning from nonrenewable energy to solar fuels via CO2 reduction

Solar energy has been used for decades for the direct production of electricity in various industries and devices; however, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuel combustion. The common feedstocks for producing such solar fuels are carbon dioxide and water, yet only the photoconversion of carbon dioxide presents the opportunity to generate liquid fuels capable of integrating into our existing infrastructure, while simultaneously removing atmospheric greenhouse gas pollution. This review presents recent advances in photochemical solar fuel production technology. Although efforts in this field have created an incredible number of methods to convert carbon dioxide into gaseous and liquid fuels, these can generally be classified under one of four categories based on how incident sunlight is utilised: solar concentration for thermoconversion (Category 1), transformation toward electroconversion (Category 2), natural photosynthesis for bioconversion (Category 3), and artificial photosynthesis for direct photoconversion (Category 4). Select examples of developments within each of these categories is presented, showing the state-of-the-art in the use of carbon dioxide as a suitable feedstock for solar fuel production.

Solar energy has been used for decades for the direct production of electricity in various industries and devices. However, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuels.

Enhanced Photocatalytic Activity of BiVO4/Bi2S3/SnS2 Heterojunction under Visible Light

Heterojunction photocatalysts have attracted a significant amount of attention due to their advantages over a single photocatalyst and, particularly, their superior spatial charge separation. Herein, the BiVO4/Bi2S3/SnS2 heterojunction was synthesized via solvothermal synthesis with different ratios of BiVO4 to SnS2. The photodegradation rate of the 0.03 BiVO4/SnS2 sample for rhodamine B removal is 2.3 times or 2.9 times greater than that of a single SnS2 or BiVO4, respectively. The chemical bond between photocatalysts is confirmed by X-ray photoelectron spectroscopy (XPS), and the synchronized shift observed in binding energies strongly indicates the electron screening effect at the heterojunction. A Z-scheme model is proposed to explain charge transfer pathway in the system, in which the formation of Bi2S3 plays a crucial role in the enhanced photocatalytic performance of the heterojunction.

Transition Metal Dichalcogenides for the Application of Pollution Reduction: A Review

The material characteristics and properties of transition metal dichalcogenide (TMDCs) have gained research interest in various fields, such as electronics, catalytic, and energy storage. In particular, many researchers have been focusing on the applications of TMDCs in dealing with environmental pollution. TMDCs provide a unique opportunity to develop higher-value applications related to environmental matters. This work highlights the applications of TMDCs contributing to pollution reduction in (i) gas sensing technology, (ii) gas adsorption and removal, (iii) wastewater treatment, (iv) fuel cleaning, and (v) carbon dioxide valorization and conversion. Overall, the applications of TMDCs have successfully demonstrated the advantages of contributing to environmental conversation due to their special properties. The challenges and bottlenecks of implementing TMDCs in the actual industry are also highlighted. More efforts need to be devoted to overcoming the hurdles to maximize the potential of TMDCs implementation in the industry.