Hydrogen generation of ammonia borane hydrolysis catalyzed by Fe22@Co58 core-shell structure

The ability of twisted nanographene for removal of Pb2+, Hg2+ and Cd2+ ions from wastewater: Computational study

CONTEXT

Heavy metal ion removal from wastewater has become a global concern due to its extensive negative effects on human health and the environment. The density functional theory is employed to investigate the possibility of removing Pb²⁺, Hg²⁺, and Cd²⁺ ions from wastewater using nano-graphene. Researchers have shown that NG can efficiently remove heavy metals from media. Additionally, it was shown that the adsorption of Pb²⁺, Hg²⁺, and Cd²⁺ ions might reduce the large pristine NG (HOMO-LUMO) gap.

METHODS

HSE06 may accurately represent NG electrical characteristics. The DFT-D3 method was also used to account for Van der Waals interactions in the present study. The results demonstrated that charge transfer and binding energy remained greater in cation-NG systems with greater electron transfer rates. Pb²⁺, Hg²⁺, and Cd²⁺ adsorption results indicated that E_gap was significantly reduced by 68%, 15%, and 21%, respectively. The Pb²⁺@NG complex exhibited the strongest oscillator strength. This may be explained by the enormous occupation number difference between the 2px orbital of the C atoms and the 6 s orbital of the Pb²⁺ cations. The greater E_bin value of Pb²⁺@NG is consistent with the increased predicted redshifts (199 nm). DFT (hybrid functional HSE06) studies that rely on time showed that the relevant complexes have "ligand-to-metal charge transfer" excitations. In general, it was found that Pb²⁺@NG had the greatest k value, binding energy, redshifts, and charge transfer rate among the complexes. The theoretical insights of this study may influence experimental efforts to identify NG-based compounds that are effective and efficient at removing pollutants from wastewater.

Synthesis of rGO supported Cu@FeCo catalyst and catalytic hydrolysis of ammonia borane

Highly dispersed Cu@FeCo/rGO catalysts have been prepared by two-step reduction method and used for hydrogen production from ammonia borane (NH₃BH₃, AB) hydrolysis at 298 K. The activity and reusability of synthesized composite catalyst were much more higher than Cu@FeCo for AB hydrolysis dehydrogenation at 298 K. Kinetic study manifested that AB hydrolysis dehydrogenation with Cu@FeCo/rGO catalysts was approaching to the first order at different catalyst concentrations. The hydrolysis reaction completed within four minutes, and its maximum hydrogen production rate reached to 7863.0 ml min^-1 g^-1 at 298 K.

Theoretical Study of Hydrogen Production from Ammonia Borane Catalyzed by Metal and Non-Metal Diatom-Doped Cobalt Phosphide

The decomposition of ammonia borane (NH3BH3) to produce hydrogen has developed a promising technology to alleviate the energy crisis. In this paper, metal and non-metal diatom-doped CoP as catalyst was applied to study hydrogen evolution from NH3BH3 by density functional theory (DFT) calculations. Herein, five catalysts were investigated in detail: pristine CoP, Ni- and N-doped CoP (CoPNi-N), Ga- and N-doped CoP (CoPGa-N), Ni- and S-doped CoP (CoPNi-S), and Zn- and S-doped CoP (CoPZn-S). Firstly, the stable adsorption structure and adsorption energy of NH3BH3 on each catalytic slab were obtained. Additionally, the charge density differences (CDD) between NH3BH3 and the five different catalysts were calculated, which revealed the interaction between the NH3BH3 and the catalytic slab. Then, four different reaction pathways were designed for the five catalysts to discuss the catalytic mechanism of hydrogen evolution. By calculating the activation energies of the control steps of the four reaction pathways, the optimal reaction pathways of each catalyst were found. For the five catalysts, the optimal reaction pathways and activation energies are different from each other. Compared with undoped CoP, it can be seen that CoPGa-N, CoPNi-S, and CoPZn-S can better contribute hydrogen evolution from NH3BH3. Finally, the band structures and density of states of the five catalysts were obtained, which manifests that CoPGa-N, CoPNi-S, and CoPZn-S have high-achieving catalytic activity and further verifies our conclusions. These results can provide theoretical references for the future study of highly active CoP catalytic materials.

Blue energy generation by the temperature-dependent properties in funnel-shaped soft nanochannels

Salinity energy generation (SEG) studies have only been done under isothermal conditions at ambient temperature. The production of salinity energy can be improved under non-isothermal conditions, albeit preserving the energy efficiency. In the current study, the effects of gradients of temperature and concentration on the salinity energy generation process were examined simultaneously. Based on the temperature-dependent properties resulting from both temperature and concentration gradients, a numerical study was carried out to determine the maximum efficiency of salinity energy generation in funnel-shaped soft nanochannels. It was presumed that a dense layer of negative charge, called a polyelectrolyte layer (PEL), is coated on the walls of the nanochannels. Co-current and counter-current modes were used to obtain temperature and concentration gradients. Under steady-state conditions, the Poisson-Nernst-Planck, Stokes-Brinkman, and energy equations were numerically solved using equivalent approaches. The results revealed that by increasing the temperature and concentration ratios in both co-current and counter-current modes of operation, the salinity energy generation increased appreciably. The salinity energy generation increased from 30 to 80 pW upon increasing the temperature ratio from 1 to 8 at a constant concentration ratio of 1000 in counter-current mode. As verified from this analysis, low-grade heat sources (<100 °C) provide considerable energy conversion in PEL grafted nanofluidic confinement when placed between electrolyte solutions of different temperatures.

Boosting polysulfides immobilization and conversion through CoS2 catalytic sites loaded carbon fiber for robust lithium sulfur batteries

The practical applications of lithium sulfur battery is impeded by the lithium polysulfide shuttling and sluggish redox kinetics. To address the issues, herein, a multifunctional host is developed by the combination of nitrogen, phosphorus co-doped carbon fiber (NPCF) and CoS₂ towards boost the soluble polysulfides adsorption and transformation. Benefiting from the NPCF originated from biomass cattail fibers, a high conductive network is provided, and shuttle effect is reduced due to the strong chemical interaction between abundant heteroatom polar sites and lithium polysulfides. Moreover, the electrocatalytic CoS₂ on the carbon skeleton facilitate lithium polysulfides conversion and lithium sulfide deposition based on the density functional theory calculations and experiments. The efficient lithium polysulfides entrapment and subsequent electrocatalytic conversion improve dynamic stability during cycling, especially for rate capability. With these advantageous features, the electrode with NPCF/CoS₂ host can deliver a good rate capability (903 and 782 mAh g^-1 at 1C and 2C, respectively) and stable cycling performance with an ultra-low capacity decay of 0.014% per cycle at 1C. Notably, the cell can achieve a high areal capacity of 4.96 mA h cm^-2 under an elevated sulfur loading of 5.0 mg cm^-2. Overall, the improvement on the electrochemical performance ascertains the validity of the design strategy based on synergy engineering, which is a highly suitable approach for energy storage and conversion application.

Metal-organic framework grown in situ on chitosan microspheres as robust host of palladium for heterogeneous catalysis: Suzuki reaction and the p-nitrophenol reduction

In this study, the metal-organic framework ZIF-8 has been successfully planted on the surface of chitosan microspheres (CS/PDA@ZIF-8) using polydopamine as connecting material for the first time, which avoids the use of expensive, non-renewable, and non-biodegradable polystyrene microspheres commonly used as templates to prepare core-shell structures. Moreover, the metal-organic framework ZIF-8 was prepared specially by three different methods and all characterized by SEM, TEM, and BET, and the ZIF-8 shell prepared at room temperature presents a regular morphology, uniform size, large specific surface area (353.1 m²/g) than the shells prepared by the other methods including. The CS/PDA@ZIF-8₂₅@Pd with high catalytic activity and high stability was especially prepared by encapsulating Pd nanoparticles into the pores of CS/PDA@ZIF-8₂₅. Notably, the fabricated catalyst performed well in an array of reactions, for example the Kapp value of the p-nitrophenol reduction reaction reached 0.0426 s^-1, and the TOF of the Suzuki coupling reaction reached 128 h^-1. In addition, the ZIF-67, UiO-66, UiO-66-NH₂, HKUST-1, and NH₂-MIL-53(Al) were also grown on chitosan microcapsules successively to prepare the core-shell microspheres, which prove the universal applicability of this strategy. And beyond that, the introduction of chitosan microspheres endows the material with biodegradable properties and excellent recycling properties.

DFT investigation of BN, AlN, and SiC fullerene sensors for arsine gas detection and removal

 Quantum chemical density functional theory (DFT) calculations were performed to investigate the adsorption of arsine (AsH3) gaseous substance at the surface of representative models of boron nitride (B16N16), aluminum nitride (Al16N16), and silicon carbide (Si16C16) fullerene-like nanocages. The results indicated that the adsorption processes of AsH3 could be taken place by each of B16N16, Al16N16, and Si16C16 nanocages. Moreover, the electronic molecular orbital properties indicated that the electrical conductivity of nanocages were changed after the adsorption processes enabling them to be used for sensor applications. To analyze the strength of interacting models, the quantum theory of atoms in molecules (QTAIM) was employed. As a typical achievement of this work, it could be mentioned that the investigated Si16C16 fullerene-like nanocage could work as a suitable adsorbent for the AsH3 gaseous substance proposing gas-sensor role for the Si16C16 fullerene-like nanocage.

Catalytic nanoparticles and magnetic nanocatalysts in organic reactions: A mini review

Nanocatalysts, as a part of nanotechnology, have been seen very useful for various fileds of applications capturing a large contribution of the world market. Indeed, several unsolved issues of catalysts have been reconsidered by employing the new nanocatalysts including single core metal atoms and ions with surrounding holes. Moreover, it was expected that the future of catalytic reactions, especially those organic ones, will deal with the nanocatalyst applications. To this aim, the features of catalytic nanoparticles and magnetic nanocatalysts regarding evaluation of their advantages and applications in organic reactions were investigated in this work. Developments of catalytic nanoparticles and magnetic nanocatalysts were discussed in this work regarding the novel applications of such materials at the nanoscale for approaching advantageous features. Increased availability, activity, and stability are very important for applications of the catalysts in various organic reactions. Therefore, it is a must to discuss features of such nanocatalytic systems to provide more information about their advantages and even disadvantages of their applications.

Ag (111) surface for ambient electrolysis of nitrogen to ammonia

In this paper, the reaction process of N₂ convert to NH₃ catalyzed by Ag (111) surface was obtained through the construction of Ag (111) surface and computational simulation. The charge transfer in the reaction process and the change of N≡N bond length are described. Since the N₂ reduction reaction (NRR) usually occurs under alkaline solution conditions, we calculated and described the coexistence of OH* and N₂. At the same time, the co-adsorption structure of OH* and N₂ at different adsorption sites was studied.