Li-S batteries with quick-charging capabilities might find this development to be advantageous.
High-throughput DFT calculations are used to assess the catalytic activity of the oxygen evolution reaction (OER) across a series of 2D graphene-based structures, specifically those containing TMO3 or TMO4 functional units. Twelve TMO3@G or TMO4@G systems were found to possess exceptionally low overpotentials, ranging from 0.33 to 0.59 V, following the screening of 3d/4d/5d transition metal (TM) atoms. The active sites are comprised of V/Nb/Ta atoms in the VB group and Ru/Co/Rh/Ir atoms in the VIII group. The mechanism of action analysis shows that the filling of outer electrons in TM atoms can be a determining factor for the overpotential value, impacting the GO* value as a key descriptor. Importantly, in addition to the widespread occurrence of OER on the pristine surfaces of systems containing Rh/Ir metal centers, the self-optimization of TM sites was undertaken, consequently leading to heightened OER catalytic performance across most of these single-atom catalyst (SAC) systems. An in-depth understanding of the OER catalytic activity and mechanism in excellent graphene-based SAC systems is facilitated by these compelling findings. The near future will witness the facilitation of non-precious, highly efficient OER catalyst design and implementation, thanks to this work.
The development of high-performance bifunctional electrocatalysts for oxygen evolution reactions and heavy metal ion (HMI) detection presents a considerable and demanding task. A novel bifunctional catalyst, composed of nitrogen and sulfur co-doped porous carbon spheres, was synthesized through a combined hydrothermal and carbonization process. This catalyst is designed for both HMI detection and oxygen evolution reactions, employing starch as a carbon source and thiourea as a nitrogen and sulfur source. C-S075-HT-C800 exhibited exceptional performance in detecting HMI and catalyzing oxygen evolution, synergistically enhanced by its pore structure, active sites, and nitrogen and sulfur functional groups. 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. High levels of Cd2+, Hg2+, and Pb2+ were successfully recovered from river water samples by the sensor. During the oxygen evolution reaction, the C-S075-HT-C800 electrocatalyst's performance, in basic electrolyte, displayed a low overpotential of 277 mV and a Tafel slope of 701 mV per decade, at a current density of 10 mA per cm2. A unique and uncomplicated approach to the design and construction of bifunctional carbon-based electrocatalysts is presented in this study.
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. Designing and synthesizing graphene derivatives, excluding any interference-causing functional groups, constituted the project's core. Using graphite reduction followed by an electrophilic reaction, a distinctive synthetic methodology was formulated. Graphene sheets readily incorporated both electron-donating groups (butyl (Bu) and 4-methoxyphenyl (4-MeOPh)) and electron-withdrawing groups (bromine (Br) and trifluoroacetyl (TFAc)), resulting in similar functionalization degrees. Electron-donating modules, notably Bu units, augmented the electron density of the carbon skeleton, leading to a substantial boost in lithium-storage capacity, rate capability, and cyclability performance. At 0.5°C and 2°C, the values were 512 and 286 mA h g⁻¹, respectively; and the capacity retention at 1C after 500 cycles reached 88%.
Future lithium-ion batteries (LIBs) are likely to benefit from the high energy density, substantial specific capacity, and environmentally friendly attributes of Li-rich Mn-based layered oxides (LLOs), positioning them as a highly promising cathode material. These materials, unfortunately, exhibit limitations such as capacity degradation, low initial coulombic efficiency, voltage decay, and poor rate performance, stemming from irreversible oxygen release and structural degradation during the cycling process. Wortmannin cost A straightforward method of triphenyl phosphate (TPP) surface treatment is presented for the creation of an integrated surface structure on LLOs, which is characterized by the presence of oxygen vacancies, Li3PO4, and carbon. When incorporated into LIBs, the treated LLOs exhibited a marked improvement in initial coulombic efficiency (ICE) of 836% and a capacity retention of 842% at 1C following 200 cycles. The improved performance of the treated LLOs is demonstrably attributable to the combined effects of the components integrated within the surface. Oxygen vacancies and Li3PO4 are responsible for suppressing oxygen evolution and accelerating lithium ion transport. Furthermore, the carbon layer effectively inhibits detrimental interfacial side reactions and reduces 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. To engineer high-energy cathode materials in LIBs, this study proposes a proficient strategy for constructing an integrated surface structure on LLOs.
Oxidizing aromatic hydrocarbons with selectivity at their C-H bonds is both an intriguing and difficult chemical endeavor, and the design of efficient heterogeneous catalysts based on non-noble metals is crucial for this reaction. A co-precipitation method and a physical mixing method were used to synthesize two different spinel (FeCoNiCrMn)3O4 high-entropy oxides, c-FeCoNiCrMn and m-FeCoNiCrMn. The catalysts produced, unlike the established, environmentally deleterious Co/Mn/Br system, selectively oxidized the CH bond in p-chlorotoluene, forming p-chlorobenzaldehyde, all within a green chemical framework. 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. Foremost, characterization results illustrated the creation of plentiful oxygen vacancies on the c-FeCoNiCrMn. The observed result underpinned the adsorption of p-chlorotoluene on the catalyst's surface and encouraged the formation of the *ClPhCH2O intermediate, as well as the desired p-chlorobenzaldehyde, as confirmed through Density Functional Theory (DFT) analysis. Beyond the established facts, scavenger tests and EPR (Electron paramagnetic resonance) results reinforced the notion that hydroxyl radicals, originating from the homolysis of hydrogen peroxide, were the principal oxidative species in this reaction. This study uncovered the function of oxygen vacancies within high-entropy spinel oxides, and also exhibited its remarkable utility in selective C-H bond oxidation, in an eco-friendly manner.
Producing methanol oxidation electrocatalysts exhibiting high activity and strong anti-CO poisoning properties remains a major obstacle. The preparation of unique PtFeIr jagged nanowires involved a straightforward strategy, placing iridium in the outer shell and platinum/iron in the inner core. The jagged Pt64Fe20Ir16 nanowire exhibits an optimal mass activity of 213 A mgPt-1 and a specific activity of 425 mA cm-2, demonstrating a significant advantage over the PtFe jagged nanowire (163 A mgPt-1 and 375 mA cm-2) and Pt/C (0.38 A mgPt-1 and 0.76 mA cm-2). FTIR spectroscopy in situ, coupled with DEMS, sheds light on the extraordinary CO tolerance's root cause, examining key non-CO pathway reaction intermediates. Density functional theory (DFT) calculations underscore the impact of iridium incorporation on the surface, illustrating a change in selectivity that redirects the reaction mechanism from a CO pathway to a different non-CO pathway. Concurrently, Ir's presence results in an optimized surface electronic structure, leading to reduced CO adsorption strength. This investigation is anticipated to promote a more comprehensive understanding of the catalytic mechanism in methanol oxidation and shed light on the structural design of improved electrocatalysts.
Developing catalysts from nonprecious metals for the production of hydrogen from cost-effective alkaline water electrolysis, ensuring both stability and efficiency, is a crucial but challenging undertaking. Nanosheet arrays of Rh-doped cobalt-nickel layered double hydroxide (CoNi LDH), enriched with oxygen vacancies (Ov), were successfully grown in-situ onto Ti3C2Tx MXene nanosheets, leading to the formation of Rh-CoNi LDH/MXene. Wortmannin cost Due to its optimized electronic structure, the synthesized Rh-CoNi LDH/MXene composite exhibited remarkable long-term stability and a low overpotential of 746.04 mV at -10 mA cm⁻² in hydrogen evolution reactions. Density functional theory calculations, coupled with experimental results, demonstrated that the inclusion of Rh dopants and Ov within CoNi LDH, along with the interfacial coupling between Rh-CoNi LDH and MXene, all contributed to a reduction in hydrogen adsorption energy, thus enhancing hydrogen evolution kinetics and ultimately accelerating the alkaline hydrogen evolution reaction (HER). A promising strategy is presented for the development and synthesis of highly efficient electrocatalysts for 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. Wortmannin cost This catalyst, based on electrochemical testing results, exhibits characteristics such as a low catalytic voltage, exceptional long-term stability, and a significant conversion rate.