The effect of varying solvents for MoS2 treatment on its catalytic efficiencies for HER and ORR

High power density output and durability of microbial fuel cells enabled by dispersed cobalt nanoparticles on nitrogen-doped carbon as the cathode electrocatalyst

To endow microbial fuel cells (MFCs) with low cost, long-term stability and high-power output, a novel cobalt-based cathode electrocatalyst (Nano-Co@NC) is synthesized from a polygonal metal-organic framework ZIF-67. After calcining the resultant ZIF-67, the as-synthesized Nano-Co@NC is characteristic of cobalt nanoparticles (Nano-Co) embedded in nitrogen-doped carbon (NC) that inherits the morphology of ZIF-67 with a large surface area. The Nano-Co particles that are highly dispersed and firmly fixed on NC not only ensure electrocatalytic activity of Nano-Co@NC toward the oxygen reduction reaction on the cathode, but also inhibit the growth of non-electrogenic bacteria on the anode. Consequently, the MFC using Nano-Co@NC as the cathode electrocatalyst demonstrates excellent performance, delivering a comparable initial power density and exhibiting far better durability than that using Pt/C (20 wt%) as the cathode electrocatalyst. The low cost and the excellent performance of Nano-Co@NC make it promising for MFCs to be used in practice.

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.

Electric Field-Driven Interfacial Alloying for in Situ Fabrication of Nano-Mo2C on Carbon Fabric as Cathode toward Efficient Hydrogen Generation

A binderless composite cathode for efficient electrocatalytic hydrogen evolution reaction (HER), Mo₂C-decorated carbon cloth (denoted as CC/MC), is simply fabricated via a novel and unique strategy which involves a solid-solid phase interfacial electrochemical reaction between carbon fiber and bulk-MoS₂ in molten NaCl-KCl (700 °C). MoS₂, evenly coated on carbon cloth (CC), is electrochemically reduced in situ and readily reacts with the carbon fibers of CC current collector to form a Mo₂C nanoparticle layer. The experiment and calculation results show that the applied electric field results in a declining migration barrier of Mo vacancies in Mo₂C lattice, which promotes the diffusion of Mo atoms into carbon across the interfacial Mo₂C layer, thereby impelling the combination of Mo with C in depth. The electrochemical tests indicate that the optimized cathode (CC/MC-2) exhibits a small overpotential of 134.4 mV at 10 mA cm^-2 and stays stable for HER in acidic media. The catalytic capacity for N₂ reduction of CC/MC-2 is analyzed. In addition, a Ni-doped Mo₂C-modified carbon fabric electrode with enhanced HER activity (η₁₀ = 96.6 mV) can be prepared through a similar process.

MoSe2 Dispersed in Stabilizing Surfactant Media: Effect of the Surfactant Type and Concentration on Electron Transfer and Catalytic Properties

Layered transition metal dichalcogenides (TMDs) have gained attention from the scientific community because of their extended range of applications. Molybdenum diselenide (MoSe₂) has been proven to be an efficient catalyst for the hydrogen evolution reaction (HER), having implications in the research of new catalysts for clean energy production. One way to produce large quantities of these materials involves the use of surfactants for liquid exfoliation. Herein, we investigate the effects of cationic, anionic, and nonionic surfactants within a concentration range on the heterogeneous electron transfer rates, electrocatalytic efficiency toward the HER of MoSe₂, and on the stability of the dispersions. We found that surfactants can have a detrimental effect on the electrocatalytic properties of the material when used above a concentration threshold. In some cases, high surfactant levels also had a negative effect on the stability of the material. This report serves to gain an understanding on how the way TMDs are prepared, processed, and stabilized can have dramatic effects on their efficiency toward HER, one of their most popular applications, and how choosing the appropriate surfactant type and concentration is crucial to gain in stability without compromising the intrinsic properties of the material.

The effects of exfoliation, organic solvents and anodic activation on the catalytic hydrogen evolution reaction of tungsten disulfide

The rational design of transition metal dichalcogenide electrocatalysts for efficiently catalyzing the hydrogen evolution reaction (HER) is believed to lead to the generation of a renewable energy carrier. To this end, our work has made three main contributions. At first, we have demonstrated that exfoliation via ionic liquid assisted grinding combined with gradient centrifugation is an efficient method to exfoliate bulk WS₂ to nanosheets with a thickness of a few atomic layers and lateral size dimensions in the range of 100 nm to 2 nm. These WS₂ nanosheets decorated with scattered nanodots exhibited highly enhanced catalytic performance for HER with an onset potential of -130 mV vs. RHE, an overpotential of 337 mV at 10 mA cm^-2 and a Tafel slope of 80 mV dec^-1 in 0.5 M H₂SO₄. Secondly, we found a strong aging effect on the electrocatalytic performance of WS₂ stored in high boiling point organic solvents such as dimethylformamide (DMF). Importantly, the HER ability could be recovered by removing the organic (DMF) residues, which obstructed the electron transport, with acetone. Thirdly, we established that the HER performance of WS₂ nanosheets/nanodots could be significantly enhanced by activating the electrode surface at a positive voltage for a very short time (60 s), decreasing the kinetic overpotential by more than 80 mV at 10 mA cm^-2. The performance enhancement was found to arise primarily from the ability of a formed proton-intercalated amorphous tungsten trioxide (a-WO₃) to provide additional active sites and favourably modify the immediate chemical environment of the WS₂ catalyst, rendering it more favorable for local proton delivery and/or transport to the active edge site of WS₂. Our results provide new insights into the effects of organic solvents and electrochemical activation on the catalytic performance of two-dimensional WS₂ for HER.

Edges of graphene and carbon nanotubes with high catalytic performance for the oxygen reduction reaction

Graphene fragments prepared using a wet-grinding method show high catalytic performance for the oxygen reduction reaction.

Surfactant-exfoliated 2D molybdenum disulphide (2D-MoS2): the role of surfactant upon the hydrogen evolution reaction

The surfactant (sodium cholate) when used in the liquid exfoliation of 2D-MoS₂ has a detrimental effect upon its electrocatalytic activity compared to pristine 2D-MoS₂ (produced without a surfactant).