Synergistic Mechanism of 0D Internal and Surface Defects Regulation Coupled with Pyroelectric Effects for Optimizing the Photoelectrocatalytic Properties of CdS

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Synergistic Mechanism of 0D Internal and Surface Defects Regulation Coupled with Pyroelectric Effects for Optimizing the Photoelectrocatalytic Properties of CdS

This paper constructed internal and surface defects to modulate the crystal structure of CdS, and investigated the synergistic impact of 0D (0-dimensional) internal and surface defects regulation coupled with pyroelectric effects for optimizing the photoelectrocatalytic properties.


Abstract

Rational defect regulation is an effective way to enhance the performance of photoelectrocatalytic (PEC) water splitting. In this paper, we firstly constructed internal and surface defects to modulate the crystal structure of CdS, and investigated the synergistic impact of 0D (0-dimensional) internal and surface defects regulation coupled with pyroelectric effects for optimizing the photoelectrocatalytic properties of CdS. It was found that the synergistic impact had a significant enhancement effect on the carrier separation and transfer, and the current density reached 3.93 mA/cm2 at 1.23 V vs. RHE increased by 16.38 times, meanwhile, the stability of the photoelectrodes was greatly promoted. The advantages and intrinsic relationships are also described: the formation of 0D dual-type of defects alters the atomic arrangement in the crystal, optimizes the energy band structure, reduces carrier recombination, and increases carrier density. What's more, the introduction of defects induces electron redistribution and changes the state of dipoles inside the crystal, thus increasing built-in electric field and generating more thermally generated carriers to optimize the pyroelectric effect. This work demonstrates the feasibility of defect modulation for optimizing pyroelectric performance and photocatalytic performance and bringing new light to PEC water splitting.

High‐Resolution X‐ray Absorption and Emission Spectroscopy for Detailed Analysis of New CO2 Methanation Catalysts

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High-Resolution X-ray Absorption and Emission Spectroscopy for Detailed Analysis of New CO2 Methanation Catalysts

A methodical approach to investigate Ni@C CO2 methanation catalysts obtained by thermal decomposition of nickel MOFs using hard X-rays is established and applied. The procedure involves high-energy-resolution X-ray absorption near-edge structure spectroscopy and X-ray emission spectroscopy in combination with ab initio FEFF calculations.


Abstract

A new approach for the characterization of CO2 methanation catalysts prepared by thermal decomposition of a nickel MOF by hard X-ray photon-in/photon-out spectroscopy in form of high energy resolution fluorescence detected X-ray absorption near edge structure spectroscopy (HERFD-XANES) and valence-to-core X-ray emission (VtC-XES) is presented. In contrast to conventional X-ray absorption spectroscopy, the increased resolution of both methods allows a more precise phase determination of the final catalyst, which is influenced by the conditions during MOF decomposition.

Ammonium and Tartrate Salts as Alternatives to Neutral Aqueous Electrolytes for Supercapacitors

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Ammonium and Tartrate Salts as Alternatives to Neutral Aqueous Electrolytes for Supercapacitors

Supercapacitors are interesting energy storage devices in terms of power density and lifetime. Organic electrolytes are frequently applied in commercial supercapacitor devices. However, their water-based counterparts are much more sustainable, cost-effective and safer. Therefore, aqueous energy storage devices are interesting alternatives. Here, aqueous Ammonium and tartrate-based electrolytes are introduced as possible candidates for applications in aqueous supercapacitors.


Abstract

Supercapacitors are promising energy storage devices in terms of power density and lifetime. Organic electrolytes are frequently applied in commercial supercapacitor devices. However, their water-based counterparts are much safer, more sustainable and cost-effective. In this study we therefore present, for the first time, aqueous tartrate-based electrolytes (sodium tartrate / ammonium tartrate) for supercapacitor applications, and relate them to well-known inorganic aqueous electrolytes like Na2SO4. Additionally, the influence of the cation on the electrochemical performance of supercapacitors is investigated using sodium and ammonium cations for comparison. We demonstrate the electrochemical performance and physicochemical properties of ammonium tartrate / sulfate and sodium tartrate / sulfate. An improvement of the conductivity in the range of 40–60 % was achieved by the exchange of sodium cation with ammonium cation. Carbon electrodes in newly introduced aqueous tartrate-based electrolytes deliver high specific capacitances up to 117 Fg−1. Furthermore, electrical double layer capacitors (EDLCs) containing 1 M ammonium tartrate display a high energy density at 0.1 Ag−1 and at 10 Ag−1 (9.88 Whkg−1 and 1.14 Whkg−1, respectively). Floating tests show excellent long-term performance. Tartrate-based EDLCs retain >80 % of their initial capacitance at 1.6 V cell voltage (120 h floating time). In the case of ammonium tartrate electrolyte, a novel metal-free and non-toxic concept for an eco-friendly supercapacitor device is proposed.

Amino Acid Residues Controlling Domain Interaction and Interdomain Electron Transfer in Cellobiose Dehydrogenase

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Amino Acid Residues Controlling Domain Interaction and Interdomain Electron Transfer in Cellobiose Dehydrogenase

Cellobiose dehydrogenase serves as an auxiliary enzyme donating electrons to lytic polysaccharide monooxygenase in biomass depolymerization, as well as a biorecognition element in biosensors due to its electron transfer capability. The involvement of two amino acids in the interdomain electron transfer process is investigated in depth with stopped-flow spectrophotometry, small-angle X-ray scattering, multistate modeling, and molecular dynamics simulations.


Abstract

The function of cellobiose dehydrogenase (CDH) in biosensors, biofuel cells, and as a physiological redox partner of lytic polysaccharide monooxygenase (LPMO) is based on its role as an electron donor. Before donating electrons to LPMO or electrodes, an interdomain electron transfer from the catalytic FAD-containing dehydrogenase domain to the electron shuttling cytochrome domain of CDH is required. This study investigates the role of two crucial amino acids located at the dehydrogenase domain on domain interaction and interdomain electron transfer by structure-based engineering. The electron transfer kinetics of wild-type Myriococcum thermophilum CDH and its variants M309A, R698S, and M309A/R698S were analyzed by stopped-flow spectrophotometry and structural effects were studied by small-angle X-ray scattering. The data show that R698 is essential to pull the cytochrome domain close to the dehydrogenase domain and orient the heme propionate group towards the FAD, while M309 is an integral part of the electron transfer pathway – its mutation reducing the interdomain electron transfer 10-fold. Structural models and molecular dynamics simulations pinpoint the action of these two residues on the domain interaction and interdomain electron transfer.

Merging Radical Brook Rearrangement and 1,5‐Hydrogen Atom Transfer: Facile Synthesis of Ketone‐Containing ɑ‐Fluoroalkyl Alcohols

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Herein, we report a cascade process that is initiated by radical Brook rearrangement and promoted by 1,5-hydrogen atom transfer. A series of α-fluoroalkyl alkyl secondary alcohols were synthesized with unactivated terminal olefins and α-fluoroalkyl-α-silyl methanols. The strategy features mild reaction conditions and broad substrate scope. The diversified down-stream transformations demonstrated the synthetic potential of the reaction.

Upcycling of Polypropylene Wastes via Catalytically C‐H Modification with Polar Olefins

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While polypropylene (PP) is one of the most widely used polyolefin materials, its post-functionalization has been a continuously researched topic in the polymer field since it could significantly improve physical and chemical properties by introducing polar groups, beneficial for development of the next generation of polyolefin materials. In this work, we describe the development of a visible-light promoted, environmentally friendly iron-catalyzed strategy and establishing of the reaction scope for C−H alkylated modification of polypropylene. Under our conditions, various polypropylenes could be functionalized with diverse polar alkenes with good levels of functionalization (LOF). The properties of the resulting polymers were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and tensile testing. Polypropylene wastes could also be upcycled. While the incorporation of the polyglycol groups enhanced hydrophilicity, the installation of the ester groups increased the miscibility with other polymers by acting as a compatibilizer for polystyrene and polyethylene.

Single‐Site Ni‐Grafted TiO2 with Diverse Coordination Environments for Visible‐Light Hydrogen Production

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Solar hydrogen production at a high efficiency holds the significant importance in the age of energy crisis, while the micro-environment manipulation of active sites on photocatalysts plays a profound role in enhancing the catalytic performance. In this work, a series of well-defined single-site Ni-grafted TiO2 photocatalysts with unique and specific coordination environments, 2,2'-bipyridine-Ni-O-TiO2 (T-Ni Bpy) and 2-Phenylpyridine-Ni-O-TiO2 (T-Ni Phpy), were constructed with the methods of surface organometallic chemistry combined with surface ligand exchange for visible-light-induced photocatalytic hydrogen evolution reaction (HER). A prominent rate of 33.82 μmol•g-1•h-1 and a turnover frequency of 0.451 h-1 for Ni are achieved over the optimal catalyst T-Ni Bpy for HER, 260-fold higher than those of Ni-O-TiO2. Fewer electrons trapped oxygen vacancies and a larger portion of long-lived photogenerated electrons (> 3 ns, ~ 52.9%), which were demonstrated by the electron paramagnetic resonance and femtosecond transient IR absorption, are corresponding to the photocatalytic HER activity over the T-Ni Bpy. The number of long-lived free electrons injected from the Ni photoabsorber to the conduction band of TiO2 is one of the determining factors for achieving the excellent HER activity.

Organometallic N‐acylhydrazones of 5‐nitrofuran and 5‐nitrothiophene based: Synthesis, electrochemical, antiparasitic evaluation, and computational study

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Organometallic N-acylhydrazones of 5-nitrofuran and 5-nitrothiophene based: Synthesis, electrochemical, antiparasitic evaluation, and computational study

We reported the synthesis, electrochemical, and antiparasitic properties and the structure–activity relationship (SAR) study of new organometallic N-acylhydrazones of general formula [R1-CH=N-NH-C(O)-(R2)] with (R1 = ferrocenyl or cyrhetrenyl; R2 = 5-nitrofuryl or 5-nitrothienyl).


In searching for new therapeutic agents for treating American trypanosomiasis and Human African trypanosomiasis, four nitroheterocyclic acylhydrazones of general formulae [R1-CH=N-NH-C(O)-(5-C4H2X)] (where R1 = ferrocenyl or cyrhetrenyl, and X = O or S) have been synthesized and characterized by spectroscopic techniques. Comparative studies of their stability by 1H-NMR and UV–Vis experiments were reported. Single-crystal X-ray diffraction confirmed the molecular structures of NF-1 and NT-2. Their X-ray crystal structures reveal that both adopt an E-configuration on the C=N moiety. Regarding the -NH-C(O)- bond, the structure of NF-1 confirmed a trans conformation, while NT-2 exhibited a cis-amide conformation. The cyclic voltammetry and electron spin resonance (ESR) experiments were conducted to study the electrochemical behavior of N-acylhydrazones. The antiparasitic activities of compounds against Trypanosoma cruzi (epimastigotes) and Trypanosoma brucei (trypomastigotes) revealed that cyrhetrenyl complexes were more effective than their ferrocenyl analogs. The cyrhetrenyl derivative NT-2 (EC50 = 2.25 μM) showed activity against T. brucei comparable to the standard drug nifurtimox (Nfx, EC50 = 3.56 μM). The ferrocenyl compound NT-1 (>200 μM) was at least two times less cytotoxic than the Nfx (88.7 μM) against the L6 rat skeletal myoblast cell line and exhibited a selectivity like Nfx toward T. brucei. Density functional theory (DFT) calculations were utilized as an approximation to explain the impact of organometallic and heterocyclic rings on antiparasitic activities. This study supported the experimental results, confirming that the cyrhetrenyl fragment in N-acylhydrazone derivatives plays a significant role in the antitrypanosomal activity, which can be attributed to an increase in positive charge on the metal.

AOMadillo: A program for fitting angular overlap model parameters

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Abstract

The angular overlap model (AOM) is an established parameterization scheme within ligand field theory (LFT). In principle, its application is fairly straightforward, but can be tedious and involve a trial-and-error approach to identify and judge the best set of parameters. With the availability of quantum chemical methods to predict d-d transitions in transition metal complexes, a rich source of computational spectroscopic data with unambiguous assignments to electronic states is available. Herein, we present AOMadillo, a software package that is designed to interface the output of ab initio LFT calculations from the ORCA suite of programs and performs a least-squares fit for a chosen AOM parameterization. Many steps of the AOM parameterization are automated, so that scans of geometric parameters and evaluations of sets of similar complexes are convenient. The fitting routine is highly configurable, allowing the efficient evaluation of different parameter sets.

2‐(o‐Tolyl) Pyridine as Ligand Improves the Efficiency in Ketone Directed ortho‐Arylation

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2-(o-Tolyl) Pyridine as Ligand Improves the Efficiency in Ketone Directed ortho-Arylation

In this work, we explore how adding a catalytic amount of an NC-type ligand improves ketone-directed ortho C−H arylation, whereas a full equivalent shuts down the transformation. Increased catalytic activity stems from the formation of a cyclometallated complex containing the NC-type ligand to provide an intermediate which accelerates the ortho-arylation of the ketone substrate.


Abstract

Herein, we report a ruthenium-catalyzed ketone directed ortho-arylation wherein the addition of a bidentate NC-type ligand, most effectively 2-(o-tolyl) pyridine, significantly enhances the C−H arylation reaction. Various aryl-alkyl ketones, including cyclic, aliphatic, and heterocyclic ones, are competent substrates, and arylboronic acid esters were used as aryl sources. However, substitution with OMe and CF3 in the aromatic ring of the ketone substrates is not tolerated, while such residues on the benzoic ester are possible. Notably, this study provides valuable insights into ketone-directed ortho arylation in the presence of 2-(o-tolyl) pyridine and adds additional options for catalyst and ligand optimization in ruthenium-catalyzed C−H functionalization.