Multistage data quantification (MSDQ) is a three-step process that enables full-scale surface extrapolation. MSDQ facilitates optimal region selection and ensures unbiased surface characterization. The extracted extrinsic properties of anode surfaces influence the catalytic activity during the oxygen evolution reaction. Hence, MSDQ provides deeper understanding of the surface morphology, thereby providing insights into processes and their parameters involved during anode fabrication.

Abstract

In this study, we developed a statistical framework, named multistage data quantification (MSDQ), to evaluate representative surface characteristics such as surface roughness, surface area, and homogeneity score of cobalt oxide-based anodes, and contributing to a deeper insight into the quality of the anode surface. Atomic force microscopy (AFM) was employed to capture the surface morphology of two anodes that have a comparable loading of cobalt oxide but exhibit distinct morphological features. Application of MSDQ exposed notable disparities in surface characteristics across these anodes, underlining the critical importance of MSDQ in precise surface characterization. Specifically, surface roughness, surface area and homogeneity score effectively elucidated the disparities in electrocatalytic activity for the oxygen evolution reaction (OER), as quantified through scanning droplet cell (SDC) measurements. By conducting a systematic comparative analysis, the respective contributions of the extrinsic surface characteristics of the anodes to the intrinsic electrocatalytic material property could be differentiated and quantified. Applications of our findings range from benchmarking of anodes to optimization of anode manufacturing processes.

The planar heteroatom doping and the axial coordination engineering are two effective strategies for breaking the symmetry of nitrogen-coordinated single-atom catalysts. This concept describes how these two types of coordination engineering enable high-efficiency activation of peroxymonosulfate as well as highly selective formation of high-valent metal-oxo species at asymmetrically coordinated single-atom sites.

Abstract

Tuning the electronic distribution of the single-atom sites in single-atom catalysts (SACs) is crucial for unlocking their catalytic potential. The four-nitrogen-coordinated transitional metal (M−N₄) configuration has been widely investigated in peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs), but restricted by the sluggish electron transfer from PMS to generate the high-valent metal-oxo (HVMO), reactive species with high redox potentials and long half-lives, for the degradation of organic pollutants in water due to its symmetric structure. Recently, the SACs with asymmetric coordination configurations are found to break the symmetric electronic distribution of M−N₄, which facilitates the O−H and O−O bond breaking in PMS, thus promoting HVMO formation. Asymmetric coordination has emerged as a novel and effective strategy for single-atom coordination modulation. In this paper, two strategies for breaking the symmetry of nitrogen-coordinated SACs by planar heteroatom doping and axial optimization engineering are outlined, and the reaction mechanisms on the formation of HVMO species over asymmetrically coordinated SACs via PMS activation are highlighted. Finally, we prospect the development of asymmetrically coordinated SACs in water purification.

Here, we have successfully synthesized highly efficient porous organic polymers (TTP-1 and PAN-T) via one-pot poly-condensation method. Silver nanoparticles grafted POP (Ag@TTP-1 and Ag@PAN-T) exhibits exceptional catalytic performances in the N-formylation and N-methylation of amines by incorporating atmospheric CO₂, which is considered as a sustainable and green approach for the formation of new C−N bond and referred as an effective reusable heterogenous catalyst.

Abstract

Chemical fixation of CO₂ for the synthesis of valuable chemicals is very demanding in the context of green and sustainable chemistry. Herein, we report highly efficient silver-loaded porous organic polymer catalysts for the exclusive N-formylation and N-methylation of amines under ambient reaction conditions using CO₂ as a green C1 source. By adjusting the solvent and temperature of the reaction, the successful production of formamides and methylamines could be accomplished with high levels of selectivity and efficiency. POP-based materials Ag@TTP-1 and Ag@PAN-T are utilized as low-cost catalysts for both the N-methylation and N-formylation of primary and secondary amines and the product yields up to 98 % could be achieved. Ag@TTP-1 demonstrated superior catalytic efficiency compared to Ag@PAN-T in the N-methylation and N-formylation reactions. This result suggests that the grafting of Ag nanoparticles onto POP surface with a high surface area plays a crucial role in these CO₂ fixation reactions. The above-mentioned catalysts (Ag@TTP-1 and Ag@PAN-T) are characterized through powder XRD, FT IR spectroscopy, FE-SEM, TEM, thermogravimetric techniques, N₂ sorption and XPS analysis. Ag-nanocatalysts demonstrated heterogeneous nature and high recycling efficiency for several cycles in this CO₂ fixation reaction.

Molecular force probe ligands apply a controlled force of extension or compression to the ligand scaffold of an intact transition metal bisphosphine complex. Using these ligands, we have quantified the effect of force on the rates of elementary reactions, namely oxidative addition and reductive elimination, and on the selectivities of catalytic transformations including the palladium-catalyzed Heck coupling and rhodium-catalyzed hydroformylation.

Abstract

The reactivity and selectivity of a transition metal catalyst is intimately related to its ligand-sphere geometry, and, in many cases, the ideal ligand geometry for one step of a catalytic cycle is poorly matched to the ideal ligand geometry for another. For this reason, methods for reversibly modulating ligand geometry on the time scale of catalytic turnover or monomer enchainment are highly desirable. Mechanical force represents a heretofore untapped approach to modulate catalyst geometry and/or reactivity, with the potential to do so on the timescale of catalytic turnover or monomer enchainment. Macroscopic mechanical forces are large, directional and localized to an extent that differentiates them from other forms of energy input such as heat or light. In this Concept, we describe our efforts to address the fundamental challenges associated with force-modulated transition metal catalysis by employing molecular force probe ligands comprising a stiff stilbene photoswitch tethered to rotationally flexible biaryl bisphosphine ligand. Our efforts to date include the modulation of catalytic activity through force-mediated ligand perturbations, quantification of the force-coupled ligand effects on the energetics of elementary organometallic transformations, and evaluation of the mechanisms of force transduction in these systems.

This study explores derivatives of H₃[PMo₁₂O₄₀], a polyoxometalate (POM), as potential redox mediators in electro-organic transformations using biobased glyceraldehyde (GLAD). The focus is on double substitution of the Mo framework with redox-active transition metals (V, Ni, Co, Mn). Electrochemical characterisation, HPLC, UV-Vis, and ³¹P-NMR spectroscopy unveil different reaction pathways as well as electronic and structural changes of the POMs.

Abstract

Polyoxometalates (POMs) are known for their unique redox properties, making them interesting candidates as redox mediators in electro-organic transformations. We investigated derivatives of H₃[PMo₁₂O₄₀], a classical Keggin-type POM, as a potential redox mediator in the indirect electrolysis of biobased glyceraldehyde (GLAD), focusing on the effects of double substitution of the Mo framework metal by redox active transition metals (Mo replaced by V, Ni, Co, Mn). By combining electrochemical techniques with HPLC, UV-Vis spectroscopy, and ³¹P-NMR spectroscopy, a comprehensive overview of the reaction pathways, as well as the electronic and structural changes of the POM during the reaction were revealed. This work not only contributes to the fundamental understanding of POMs as redox mediators, but also paves the way for innovative development of sustainable and environmentally friendly electro-organic transformations.

The Quaternary material NCMFe was prepared by the co-precipitation method, and the properties of the material were improved by exploring the amount of Cr doping. The cycle and rate properties of the modified battery were greatly improved.

Abstract

A series of cathode materials, Li[Ni_0.6Co_0.12Mn_0.2Fe_0.08]_1-xCr_xO₂ (x=0, 0.02, 0.04, 0.06), are synthesized via the co-precipitation method. Structural characterization shows that Cr³⁺ ions are successfully incorporated into the material structure and evenly dispersed on the surface of crystal particles with other metal elements. The Cr-doped material shows a well-defined hexagonal layered structure with less cation mixing, and the increase in interionic and interlayer distances is beneficial for the transport of lithium ions. Compared to the pure NCMFe phase, the cyclic and rate performances of the Cr-doped quaternary materials have been significantly improved. Among them, the 4Cr material exhibits the best electrochemical performance. The capacity retention rate after 50 charge-discharge cycles at 0.1 C was increased from 74.83 % to 87.32 %. The rate performance has also increased from 87.6 % to 92.69 %. The Cr-doped cathode can reduce the charge transfer resistance and enhance the stability of the layered structure, which results in outstanding electrochemical performance of the Cr-doped cathode. CV and EIS tests were conducted on materials with various Cr doping levels, further confirming that Cr doping can reduce the degree of polarization in electrode materials, enhance charge and discharge reversibility, and reduce the charge transfer resistance of materials.

The Front Cover shows a humanoid making pulses to the ropes attached to a beta (BEA) zeolite pore topology. The catalyst is used in the oligomerization of ethylene to higher olefins. In their Research Article, P. Castaño et al. discuss how using pulse reaction and adsorption together with steady-state conditions allows access to insights into the effect of Ni, acid sites, and pore topology during the reaction.More information can be found in the Research Article by P. Castaño et al.

Reactive-adsorptive and pulsed–continuous ethylene feeding on MFI, BEA zeolites, and Ni/zeolite catalysts reveal ethylene adsorption and oligomerization steps. The dynamics of these steps (initial and pseudo-steady state) and the impact of zeolite pore topology, Ni, and acid sites on the reaction-adsorption mechanisms are investigated.

Abstract

Herein, four catalysts, consisting of either MFI or BEA as the zeolite framework in the presence or absence of Ni, are compared to explore the individual and collective adsorptive and catalytic contributions of pore topology, Ni sites, and acid sites. Both continuous and pulsed chemisorption/reaction experiments are used to obtain a complete picture of the time-dependent adsorption-desorption behavior, reaction mechanisms, and deactivation steps. The methodology highlights the effect of acid sites, especially during the initial stages of reaction and in the BEA-based catalysts, which have higher acidity at a given Si/Al ratio. In addition, Ni accelerates the reaction and improves the selectivity towards intermediate oligomers. However, the tendency for the most active Ni and acid sites to saturate and deactivate more rapidly than the less active ones may lead to misinterpretation when using the continuous reactor alone. Hence, the dominant mechanisms over the different catalyst sites and reaction times are discussed based on the combined steady and dynamic experiments.

The Cover Feature shows the efforts of scientists to modify transition-metal containing MFI topologies to achieve the highest activity and N₂ selectivity for NH₃-SCR-DeNO _x and NH₃ oxidation. MFI-based catalysts are still used commercially for these processes and are of great interest for future study, in particular to better understand structure-activity relationships. In their Review, M. Jabłońska, M. E. Potter and A. M. Beale critically review and discuss the salient physico-chemical properties that influence the performance of these catalysts together with the strategies for the development of ZSM-5 based catalysts with enhanced catalytic lifetime, supported by the investigations of reaction mechanisms.More information can be found in the Review by M. Jabłońska, A. M. Beale et al.

Ru−O bonding interactions are enhanced via Ir regulation, stabilizing the solvation of RuO_x at high potentials, thus greatly improving the activity and stability towards OER.

Abstract

Highly active and stable oxygen evolution reaction (OER) catalysts are crucial for the large-scale application of proton exchange membrane water electrolyzers. However, the dynamic reconfiguration of the catalyst surface structure and active centers is still undefined, which greatly hinders the development and application of efficient OER catalysts. Herein, we report an Ir_0.3Ru_0.7O_x/C catalyst with a facile low-temperature synthesis route, which can reach 10 mA cm⁻² at an overpotential of 217 mV with a Tafel slope as low as 39.4 mV dec⁻¹, and yields a mass activity 61 times that of commercial IrO₂/C at an overpotential of 300 mV. The lattice oxygen structure of RuO_x is stabilized by the introduction of Ir species, thus greatly promoting the OER activity and durability. Further in situ Raman reveals that RuO_x emerges as the active species at high potentials, and Ru−O bonding interactions are enhanced with Ir regulation, stabilizing the solvation of Ru at high potentials and accelerating the nucleophilic attack of water molecules, leading to the improved OER performance. This work deepens the fundamental understanding of OER and offers an effective way to advance the utilization of Ru-based OER catalysts.