Li-S batteries with quick-charging capabilities might find this development to be advantageous.
Exploring the catalytic activity of the oxygen evolution reaction (OER) in a series of 2D graphene-based systems, incorporating TMO3 or TMO4 functional units, involves the use of high-throughput DFT calculations. The screening of 3d/4d/5d transition metals (TM) atoms led to the identification of twelve TMO3@G or TMO4@G systems, each demonstrating an exceptionally low overpotential of between 0.33 and 0.59 volts. The active sites were provided by V/Nb/Ta atoms in the VB group and Ru/Co/Rh/Ir atoms in the VIII group. Through mechanism analysis, it is evident that the distribution of outer electrons in TM atoms substantially affects the overpotential value, doing so via manipulation of the GO* value as a descriptive parameter. Furthermore, in addition to the overall scenario of OER on the clean surfaces of systems containing Rh/Ir metal centers, the self-optimizing procedure for TM sites was implemented, resulting in substantial OER catalytic activity for most of these single-atom catalyst (SAC) systems. The remarkable performance of graphene-based SAC systems in the OER is further elucidated by these significant findings on their catalytic activity and mechanism. Through this work, the design and implementation of non-precious, highly efficient OER catalysts will be accelerated in the near future.
Developing high-performance bifunctional electrocatalysts for oxygen evolution reaction and heavy metal ion (HMI) detection is a considerable and challenging task. Through a hydrothermal method followed by carbonization, a novel bifunctional catalyst, a nitrogen and sulfur co-doped porous carbon sphere, was fabricated for both HMI detection and oxygen evolution reactions. This material utilized starch as a carbon source and thiourea as the nitrogen and sulfur precursor. The synergistic impact of pore structure, active sites, and nitrogen and sulfur functional groups conferred upon C-S075-HT-C800 excellent HMI detection performance and oxygen evolution reaction activity. The C-S075-HT-C800 sensor, under optimized conditions, exhibited detection limits (LODs) of 390 nM for Cd2+, 386 nM for Pb2+, and 491 nM for Hg2+, each when measured separately, and associated sensitivities of 1312 A/M, 1950 A/M, and 2119 A/M, respectively. In river water samples, the sensor achieved substantial recoveries of the target elements: Cd2+, Hg2+, and Pb2+. Within the basic electrolyte, the oxygen evolution reaction using the C-S075-HT-C800 electrocatalyst yielded a 701 mV/decade Tafel slope and a 277 mV low overpotential at a current density of 10 mA per square centimeter. This investigation presents a novel and straightforward approach to the design and fabrication of bifunctional carbon-based electrocatalysts.
Organic functionalization of graphene's framework enhanced lithium storage capabilities, but the introduction of electron-withdrawing and electron-donating groups lacked a consistent, universal approach. The principal work involved the design and synthesis of graphene derivatives; interference-causing functional groups were explicitly avoided. Accordingly, a unique synthetic methodology was developed, employing a graphite reduction step followed by an electrophilic reaction. The comparable functionalization levels on graphene sheets were achieved by the facile attachment of electron-withdrawing groups, including bromine (Br) and trifluoroacetyl (TFAc), and their electron-donating counterparts, namely butyl (Bu) and 4-methoxyphenyl (4-MeOPh). By enriching the electron density of the carbon skeleton, particularly with Bu units, which are electron-donating modules, the lithium-storage capacity, rate capability, and cyclability were substantially improved. At 0.5°C and 2°C, the respective values for mA h g⁻¹ were 512 and 286; furthermore, 88% capacity retention was observed after 500 cycles at 1C.
Li-rich Mn-based layered oxides, or LLOs, have emerged as a highly promising cathode material for next-generation lithium-ion batteries, owing to their high energy density, significant specific capacity, and environmentally benign nature. The cycling of these materials leads to undesirable characteristics, including capacity degradation, low initial coulombic efficiency, voltage decay, and poor rate performance, owing to the irreversible oxygen release and accompanying structural damage. DX3-213B in vitro Employing triphenyl phosphate (TPP), we demonstrate a straightforward surface treatment technique for LLOs, producing an integrated surface structure that includes oxygen vacancies, Li3PO4, and carbon. Treated LLOs, when utilized in LIBs, displayed a substantial boost in initial coulombic efficiency (ICE) of 836%, along with an enhanced capacity retention of 842% at 1C after 200 cycles. A likely explanation for the improved performance of the treated LLOs is the synergistic effect of the integrated surface components. The presence of oxygen vacancies and Li3PO4 is critical in suppressing oxygen evolution and facilitating lithium ion movement. Simultaneously, the carbon layer inhibits unwanted interfacial reactions and decreases the dissolution of transition metals. Moreover, electrochemical impedance spectroscopy (EIS) and the galvanostatic intermittent titration technique (GITT) demonstrate an improved kinetic characteristic of the processed LLOs cathode, and ex situ X-ray diffraction analysis reveals a reduced structural alteration of TPP-treated LLOs throughout the battery reaction. The creation of high-energy cathode materials in LIBs is facilitated by the effective strategy, detailed in this study, for constructing an integrated surface structure on LLOs.
While the selective oxidation of C-H bonds in aromatic hydrocarbons is an alluring goal, the development of efficient, heterogeneous catalysts based on non-noble metals remains a challenging prospect for this reaction. Using the co-precipitation method and the physical mixing method, two varieties of (FeCoNiCrMn)3O4 spinel high-entropy oxides were prepared: c-FeCoNiCrMn and m-FeCoNiCrMn. The catalysts developed, unlike the standard, environmentally detrimental Co/Mn/Br system, effectively facilitated the selective oxidation of the carbon-hydrogen bond in p-chlorotoluene to synthesize p-chlorobenzaldehyde, utilizing a green chemistry method. m-FeCoNiCrMn's larger particle size compared to c-FeCoNiCrMn's smaller particle size, ultimately leads to a lower specific surface area and thus reduced catalytic activity in the former material. Significantly, characterization results showcased that a substantial number of oxygen vacancies arose within the c-FeCoNiCrMn structure. This outcome not only facilitated the adsorption of p-chlorotoluene onto the catalyst surface, but also promoted the formation of the *ClPhCH2O intermediate and the desired p-chlorobenzaldehyde, as evidenced by Density Functional Theory (DFT) calculations. Moreover, assessments of scavenger activity and EPR (Electron paramagnetic resonance) spectroscopy revealed that hydroxyl radicals, products of hydrogen peroxide homolysis, were the key oxidative species in this reaction. The research illuminated the significance of oxygen vacancies within spinel high-entropy oxides, concurrently showcasing its potential in selectively oxidizing C-H bonds via an environmentally friendly process.
To engineer highly active methanol oxidation electrocatalysts possessing excellent CO poisoning resistance is still a considerable challenge. A simple method was used to fabricate distinctive PtFeIr jagged nanowires, with Ir situated in the shell and Pt/Fe at the core. The Pt64Fe20Ir16 jagged nanowire, with a mass activity of 213 A mgPt-1 and a specific activity of 425 mA cm-2, demonstrates a substantial performance advantage compared to PtFe jagged nanowires (163 A mgPt-1 and 375 mA cm-2) and Pt/C (0.38 A mgPt-1 and 0.76 mA cm-2). The origin of remarkable CO tolerance, in terms of key reaction intermediates in the non-CO pathway, is illuminated by in-situ FTIR spectroscopy and differential electrochemical mass spectrometry (DEMS). Density functional theory (DFT) simulations solidify the evidence that the addition of iridium to the surface induces a change in the reaction selectivity, transitioning from a carbon monoxide pathway to a non-carbon monoxide one. The presence of Ir, meanwhile, serves to fine-tune the surface electronic structure, thus reducing the strength of CO adhesion. Through this work, we aim to advance the understanding of the catalytic mechanism in methanol oxidation reactions, and offer beneficial insights into the structural design of more effective electrocatalysts.
Producing stable and efficient hydrogen from affordable alkaline water electrolysis using nonprecious metal catalysts is a crucial, yet challenging, endeavor. Rh-CoNi LDH/MXene composite materials were successfully prepared by in-situ growth of Rh-doped cobalt-nickel layered double hydroxide (CoNi LDH) nanosheet arrays with abundant oxygen vacancies (Ov) directly onto Ti3C2Tx MXene nanosheets. intramedullary tibial nail The Rh-CoNi LDH/MXene composite, synthesized, demonstrated exceptional long-term stability and a low overpotential of 746.04 mV at -10 mA cm⁻² for hydrogen evolution, attributable to its optimized electronic structure. Through experimental verification and density functional theory calculations, it was shown that the introduction of Rh dopants and Ov into CoNi LDH, alongside the optimized interface with MXene, affected the hydrogen adsorption energy positively. This optimization propelled hydrogen evolution kinetics, culminating in an accelerated alkaline hydrogen evolution reaction. This investigation details a promising technique for the design and synthesis of highly efficient electrocatalysts applicable to electrochemical energy conversion devices.
The high production costs of catalysts necessitate a focus on bifunctional catalyst design, a method capable of yielding the best results with the least amount of investment. The simultaneous oxidation of benzyl alcohol (BA) and the reduction of water is achieved through a one-step calcination procedure to produce a bifunctional Ni2P/NF catalyst. Nutrient addition bioassay The catalyst has proven through electrochemical testing to have a low catalytic voltage, long-term stability and high conversion rates.