Activity Descriptors Research Articles

Identifying Electrocatalytic Activity Sequence of Metal Phthalocyanines for the Hydrogen Peroxide Oxidation Reaction

The hydrogen peroxide oxidation reaction (HPOR) plays a vital role in the emerging H2-H2O2 cycle energy storage system, in which the rational design of HPOR electrocatalyst is essential for achieving high system efficiency. Herein, we establish the HPOR activity trends using structurally well-defined metal phthalocyanines (MPc) as model catalysts via a combined experimental and computational approach. The measured activity sequence follows the order of CoPc > FePc > MnPc > ZnPc > H2Pc > NiPc > CuPc based on their site-normalized exchange current (i 0-s). Theoretical calculations indicate that the binding free energy of hydroperoxyl intermediate, HOO*, on MPc (ΔG HOO*) is the activity descriptor for HPOR. A volcano-type activity trend is observed by correlating the logarithm of i 0-s (logi 0-s) with the ΔG HOO* values and agrees with the theoretical predictions. This HPOR activity trend provides insights into the design of highly active electrocatalysts for HPOR and related energy applications.

Role of Electrolyte pH on Water Oxidation for Iridium Oxides.

Understanding the effect of noncovalent interactions of intermediates at the polarized catalyst-electrolyte interface on water oxidation kinetics is key for designing more active and stable electrocatalysts. Here, we combine operando optical spectroscopy, X-ray absorption spectroscopy (XAS), and surface-enhanced infrared absorption spectroscopy (SEIRAS) to probe the effect of noncovalent interactions on the oxygen evolution reaction (OER) activity of IrOx in acidic and alkaline electrolytes. Our results suggest that the active species for the OER (Ir4.x+-*O) binds much stronger in alkaline compared with acid at low coverage, while the repulsive interactions between these species are higher in alkaline electrolytes. These differences are attributed to the larger fraction of water within the cation hydration shell at the interface in alkaline electrolytes compared to acidic electrolytes, which can stabilize oxygenated intermediates and facilitate long-range interactions between them. Quantitative analysis of the state energetics shows that although the *O intermediates bind more strongly than optimal in alkaline electrolytes, the larger repulsive interaction between them results in a significant weakening of *O binding with increasing coverage, leading to similar energetics of active states in acid and alkaline at OER-relevant potentials. By directly probing the electrochemical interface with complementary spectroscopic techniques, our work goes beyond conventional computational descriptors of the OER activity to explain the experimentally observed OER kinetics of IrOx in acidic and alkaline electrolytes.

Cooperative Effects Drive Water Oxidation Catalysis in Cobalt Electrocatalysts through the Destabilization of Intermediates.

A barrier to understanding the factors driving catalysis in the oxygen evolution reaction (OER) is understanding multiple overlapping redox transitions in the OER catalysts. The complexity of these transitions obscure the relationship between the coverage of adsorbates and OER kinetics, leading to an experimental challenge in measuring activity descriptors, such as binding energies, as well as adsorbate interactions, which may destabilize intermediates and modulate their binding energies. Herein, we utilize a newly designed optical spectroelectrochemistry system to measure these phenomena in order to contrast the behavior of two electrocatalysts, cobalt oxyhydroxide (CoOOH) and cobalt-iron hexacyanoferrate (cobalt-iron Prussian blue, CoFe-PB). Three distinct optical spectra are observed in each catalyst, corresponding to three separate redox transitions, the last of which we show to be active for the OER using time-resolved spectroscopy and electrochemical mass spectroscopy. By combining predictions from density functional theory with parameters obtained from electroadsorption isotherms, we demonstrate that a destabilization of catalytic intermediates occurs with increasing coverage. In CoOOH, a strong (∼0.34 eV/monolayer) destabilization of a strongly bound catalytic intermediate is observed, leading to a potential offset between the accumulation of the intermediate and measurable O2 evolution. We contrast these data to CoFe-PB, where catalytic intermediate generation and O2 evolution onset coincide due to weaker binding and destabilization (∼0.19 eV/monolayer). By considering a correlation between activation energy and binding strength, we suggest that such adsorbate driven destabilization may account for a significant fraction of the observed OER catalytic activity in both materials. Finally, we disentangle the effects of adsorbate interactions on state coverages and kinetics to show how adsorbate interactions determine the observed Tafel slopes. Crucially, the case of CoFe-PB shows that, even where interactions are weaker, adsorption remains non-Nernstian, which strongly influences the observed Tafel slope.

Electrocatalytic Mechanism and Sabatier Principle in C2N-Supported Atomically Dispersed Catalysts for the Sulfur Reduction Reaction in Lithium-Sulfur Batteries.

The sluggish kinetics of the sulfur reduction reaction (SRR) impedes the practical application of lithium-sulfur batteries (LSBs). Electrocatalysts are necessary to expedite the conversion of polysulfides. Here, we systematically investigate the chemical mechanisms and size dependence of catalytic activities toward the SRR from Li2S4 to Li2S on single-, double-, and triple-atom catalysts supported on C2N (Mn@C2N, where M is a 3d transitional metal and n = 1-3) as model systems by using first-principles calculations and a comprehensive electrocatalytic model. Our results reveal that the adsorption strength of the LiS• intermediate is identified as an optimal descriptor for catalytic activity. M1@C2N exhibits superior stability and exceptional activity compared to those of the other two catalyst types. Cu1@C2N exhibits the lowest overpotential of 0.426 V. Li embedding or a prelithiation strategy verifies the therein Sabatier principle. This work emphasizes the precise control of the active site structure and microenvironment in catalytic SRR and offers guidance for the design of electrocatalysts for metal-sulfur batteries.

Cooperative Effect of Cations and Catalyst Structure in Tuning Alkaline Hydrogen Evolution on Pt Electrodes.

The kinetics of hydrogen evolution reaction (HER) in alkaline media, a reaction central to alkaline water electrolyzers, is not accurately captured by traditional adsorption-based activity descriptors. As a result, the exact mechanism and the main driving force for the water reduction or HER rate remain hotly debated. Here, we perform extensive kinetic measurements on the pH- and cation-dependent HER rate on Pt single-crystal electrodes in alkaline conditions. We find that cations interacting with Pt step sites control the HER activity, while they interact only weakly with Pt(111) and Pt(100) terraces and, therefore, cations do not affect HER kinetics on terrace sites. This is reflected by divergent activity trends as a function of pH as well as cation concentration on stepped Pt surfaces vs Pt surfaces that do not feature steps, such as Pt(111). We show that HER activity can be optimized by rationally tuning these step-cation interactions via selective adatom deposition at the steps and by choosing an optimal electrolyte composition. Our work shows that the catalyst and the electrolyte must be tailored in conjunction to achieve the highest possible HER activity.

Thermodynamic and Kinetic Activity Descriptors for the Catalytic Hydrogenation of Ketones.

Activity descriptors are a powerful tool for the design of catalysts that can efficiently utilize H2 with minimal energy losses. In this study, we develop the use of hydricity and H- self-exchange rates as thermodynamic and kinetic descriptors for the hydrogenation of ketones by molecular catalysts. Two complexes with known hydricity, HRh(dmpe)2 and HCo(dmpe)2, were investigated for the catalytic hydrogenation of ketones under mild conditions (1.5 atm and 25 °C). The rhodium catalyst proved to be an efficient catalyst for a wide range of ketones, whereas the cobalt catalyst could only hydrogenate electron-deficient ketones. Using a combination of experiment and electronic structure theory, thermodynamic hydricity values were established for 46 alkoxide/ketone pairs in both acetonitrile and tetrahydrofuran solvents. Through comparison of the hydricities of the catalysts and substrates, it was determined that catalysis was observed only for catalyst/ketone pairs with an exergonic H- transfer step. Mechanistic studies revealed that H- transfer was the rate-limiting step for catalysis, allowing for the experimental and computation construction of linear free-energy relationships (LFERs) for H- transfer. Further analysis revealed that the LFERs could be reproduced using Marcus theory, in which the H- self-exchange rates for the HRh/Rh+ and ketone/alkoxide pairs were used to predict the experimentally measured catalytic barriers within 2 kcal mol-1. These studies significantly expand the scope of catalytic reactions that can be analyzed with a thermodynamic hydricity descriptor and firmly establish Marcus theory as a valid approach to develop kinetic descriptors for designing catalysts for H- transfer reactions.

Regulating Excess Electrons in Reducible Metal Oxides for Enhanced Oxygen Evolution Reaction Activity: A Mini-Review.

Identifying a universal activity descriptor for metal oxides, akin to the d-band center for transition metals, remains a significant challenge in catalyst design, largely due to the intricate electronic structures of metal oxides. This review highlights a major advancement in formulating the number of excess electrons (NEE) as an activity descriptor for oxygen evolution reaction (OER) on reducible metal oxide surfaces. We elaborate on the quantitative relationship between NEE and the adsorption properties of OER intermediates, and unveil the decisive role of the octet rule on the OER performance of these oxides. This insight provides a robust theoretical basis for designing effective OER catalysts. Moreover, we discuss critical experimental evidence supporting this theory and summarize recent advances in employing NEE as a guiding principle for developing highly efficient OER catalysts experimentally.

Fundamental Understanding of Hydrogen Evolution Reaction on Zinc Anode Surface: A First-Principles Study

HighlightsThe reaction mechanisms of hydrogen evolution reaction (HER) on various crystal surfaces of zinc anode have been systematically investigated by first-principle calculations.Both the thermodynamic and kinetic aspects of HER have been studied to reveal the relative HER activity of several crystal surface of zinc anode.The generalized coordination number of surface Zn atoms are proposed as a key descriptor of HER activity of Zn anode.

Appraisal of National Institute for Health and Care Research activity in primary care in England: cross-sectional study.

The National Institute for Health and Care Research (NIHR) was set up to enhance clinical and health research activity in a variety of National Health Service (NHS) healthcare settings, including primary care. To appraise how overall General Practitioner (GP) practice performance, location, and staffing levels may interact with NIHR Portfolio activity in primary care in England. Cross-sectional summary of GP practice research activity and practice descriptors; complete data from 6,171 GP practices was collated from NIHR (using data for 2013-2023 for Portfolio studies), Public Health England, Care Quality Commission, and NHS Digital sources, respectively. In primary care, 1 million patients have been recruited into NIHR Portfolio studies in the last decade. The top 10% of practices-measured by different studies recruited to-contributed over 50% of that accrual. When the top decile of GP practices is compared to the 20% least active GP practices, research activity is significantly and individually linked with larger GP practices. Furthermore, it is significantly yet modestly associated with GP practice performance (positive patient feedback, Care Quality Commission rating), lower locality deprivation levels, and lower patient to GP ratios. Research activity in GP practices is-as seen previously with hospitals-significantly linked with better GP practice performance and patient feedback. Practice list size and staffing levels in particular interact with the aforementioned. This should be taken into account when determining strategies to increase patient and GP practice participation in NIHR Portfolio research studies.

Hetero-epitaxial grown Pt@Au core-shell bimetallic nanoparticles on reduced graphene oxide (RGO) as electrocatalyst for oxygen reduction reaction in alkaline media

The core-shell structured Pt@Aubimetallic nanoparticles (NPs) were decorated on the reduced graphene oxide (RGO) surface by a heteroepitaxial growth method. The morphological details of Pt@Au/RGO core/shell bimetallic NPs were assessed by high-resolution transmission electron microscopy (HR-TEM), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). Electron microscopy results revealed that Pt@Au particles of 3.4 nm were firmly attached to RGO sheets. The electrochemical response of Pt@Au/RGO nanostructured electrocatalyst was measured through cyclic voltammetry (CV) at room temperature in 0.1 M KOH solution. Oxygen reduction reaction (ORR) efficacies of Pt@Au/RGO were evaluated by linear sweep voltammetry (LSV) by rotating catalyst-coated glassy carbon (GC) electrode at different rotation speeds in oxygen saturated 0.1 M KOH solution. The electrochemical activity descriptors (half-wave potential, onset potential, limiting current density) were assessed from ORR polarisation curves. The results revealed that Pt@Au/RGO bimetallic NPs showed enhanced higher catalytic activity towards ORR compared to commercial Pt/C catalyst as well as similarly synthesised Pt/RGO and Au/RGO. The enhanced catalytic activity of Pt@Au/RGO electrocatalyst might result from the core/shell structure with a tiny Pt core and a thin Au shell, as well as the synergistic effects of Au and Pt.

Biomimetic Control over Bimetallic Nanoparticle Structure and Activity via Peptide Capping Ligand Sequence.

The controlled design of bimetallic nanoparticles (BNPs) is a key goal in tailoring their catalytic properties. Recently, biomimetic pathways demonstrated potent control over the distribution of different metals within BNPs, but a direct understanding of the peptide effect on the compositional distribution at the interparticle and intraparticle levels remains lacking. We synthesized two sets of PtAu systems with two peptides and correlated their structure, composition, and distributions with the catalytic activity. Structural and compositional analyses were performed by a combined machine learning-assisted refinement of X-ray absorption spectra and Z-contrast measurements by scanning transmission electron microscopy. The difference in the catalytic activities between nanoparticles synthesized with different peptides was attributed to the details of interparticle distribution of Pt and Au across these markedly heterogeneous systems, comprising Pt-rich, Au-rich, and Au core/Pt shell nanoparticles. The total amount of Pt in the shells of the BNPs was proposed to be the key catalytic activity descriptor. This approach can be extended to other systems of metals and peptides to facilitate the targeted design of catalysts with the desired activity.

First-principle calculations study of oxygen reduction electrocatalyst: Single transition metal supported on a brand-new graphitic carbon nitride (g-C7N3) substrate

Single-atom catalysts (SACs) possess promising potential as materials to catalyze oxygen reduction reaction (ORR) on account of high atomic utilization efficiency, tunable electronic structure, and exceptional catalytic performance. The ORR activities of graphite carbonitride (g-C7N3) supported 3d, 4d, and 5d transition metals are investigated. Eleven kinds of TM-C7N3 structures have been found to have good stability by computing formation energy and dissolution potential. Furthermore, density of states analysis shows a strong interaction of the metal atom and the coordination N atoms, which gives satisfactory stability of TM-C7N3. Among eleven TM-C7N3, the binding energy of reaction species on Rh-C7N3, Ni-C7N3, and Pt-C7N3 are closer to those of Pt(111), showing that they have good ORR activity. In addition, good linear relationships exist between the adsorption free energy of *OH (∆G*OH) and that of *OOH and *O, implying that ∆G*OH can be put forward as a trustworthy activity descriptor. Promisingly, the ηORR values of Rh-C7N3, Ni-C7N3, and Pt-C7N3 are 0.32, 0.38, and 0.44 V, respectively, even lower than the overpotential value of Pt(111). This suggests that these three catalysts demonstrate superior catalytic activity compared to Pt(111).

An antibacterial lead identification of novel 1,3,4-oxadiazole derivatives based on molecular computer aided design approaches

Merging Density Functional Theory (DFT) with the Quantitative Structure-Activity Relationship (2D/3D-QSAR) modeling represents a promising avenue for exploring antibacterial activity and discovering potential drugs effective against both gram-positive and gram-negative microorganisms. In this study, we employed this integrated approach to investigate a newly synthesized and promising class of 1,3,4-oxadiazole derivatives renowned for their high performance as antibacterial agents. To ensure an accurate characterization and thorough description of the targeted biological activity, we systematically evaluated various DFT functionals to precisely predict the geometrical and electronic descriptors of the investigated compounds. These descriptors were crucial for developing and validating the proposed 2D/3D-QSAR models. Our results reveal that the introduction of a donor group enhances the antibacterial activity of the derivatives. The analysis of molecular descriptors underscores the positive impact of this modification on the compounds' efficacy against bacteria. Additionally, our experimental compounds exhibit favorable characteristics concerning oral bioavailability, a crucial aspect in drug development. The identification of robust correlations between antibacterial activity and specific descriptors was achieved by conducting an extensive analysis that encompassed multiple linear regression (MLR), Random Forest (RF), and Artificial Neural Networks (ANN). Subsequently, a partial least squares (PLS) model was employed to construct 3D-QSAR models based on the Comparative Molecular Field Analysis (CoMFA) and Comparative Similarity Indices Analysis (CoMSIA) descriptors. Validation of the output models was performed using leave-one-out and bootstrapping strategies. The resultant 2D/3D-QSAR models demonstrated a high correlation between experimental and predicted activity values. Leveraging these models, the developed MLR model, expressed as pMIC = -12.704 + 0.260 logP – 6.104 10-03 SAG – 51.385 qN33, serves as a valuable tool for predicting antibacterial activity. we indicate that the machine learning methods, Artificial Neural Networks (ANN) and Random Forest (RF), outperform traditional models in accurately predicting antibacterial activity. We designed ten novel molecules, subjecting them to molecular docking and molecular dynamics simulations to predict their optimal postures when docked in the target and gain insights into the formed interactions. Additionally, Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) analysis was applied to discern the potential behavior of these novel compounds in the human body. As a result, the newly suggested chemical, X4, X10, exhibited robust inhibitory potential against gram-negative microbes.

The Relevance of the Interfacial Water Reactivity for Electrochemical CO Reduction on Copper Single Crystals.

The electrochemical reduction of CO2 is an important electrolysis reaction that enables the conversion of a waste gas to fuels or value-added chemicals. To make this reaction viable, a profound understanding of central intermediate steps, such as the CO electroreduction, is required. On Cu, the CO reduction reaction (CORR) is intimately linked to the hydrogen evolution reaction (HER) that proceeds via the reduction of water in alkaline or neutral electrolytes. Here, we demonstrate that the interaction of water or more specifically the water reduction kinetics on differently smooth Cu(100) and Cu(111) surfaces during the CORR in alkaline media significantly governs the CORR. On Cu(111), faster HER kinetics and the highest CORR activity are observed, even though HER and CORR onsets are more negative. While on Cu(100) small Cu ad-island clusters form in the cathodic potential range only when CO is present, structural changes appear on a larger length scale on Cu(111) both under CORR conditions and when no CO is present. These differences in the reconstruction characteristics may be attributed to the dominance of either the CORR and its intermediates or the HER on the different Cu surfaces. Therefore, the interfacial water reactivity is considered an essential activity descriptor for the CORR on Cu in alkaline media.

Electrodegradation of nitrogenous pollutants in sewage: from reaction fundamentals to energy valorization applications.

The excessive accumulation of nitrogen pollutants (mainly nitrate, nitrite, ammonia nitrogen, hydrazine, and urea) in water bodies seriously disrupts the natural nitrogen cycle and poses a significant threat to human life and health. Electrolysis is considered a promising method to degrade these nitrogenous pollutants in sewage, with the advantages of high efficiency, wide generality, easy operability, retrievability, and environmental friendliness. For particular energy devices, including metal-nitrate batteries, direct fuel cells, and hybrid water electrolyzers, the realization of energy valorization from sewage purification processes (e.g., valuable chemical generation, electricity output, and hydrogen production) becomes feasible. Despite the progress in the research on pollutant electrodegradation, the development of electrocatalysts with high activity, stability, and selectivity for pollutant removal, coupled with corresponding energy devices, remains a challenge. This review comprehensively provides advanced insights into the electrodegradation processes of nitrogenous pollutants and relevant energy valorization strategies, focusing on the reaction mechanisms, activity descriptors, electrocatalyst design, and actuated electrodes and operation parameters of tailored energy conversion devices. A feasibility analysis of electrodegradation on real wastewater samples from the perspective of pollutant concentration, pollutant accumulation, and electrolyte effects is provided. Challenges and prospects for the future development of electrodegradation systems are also discussed in detail to bridge the gap between experimental trials and commercial applications.

Hydrogen oxidation electrocatalysts for anion-exchange membrane fuel cells: activity descriptors, stability regulation, and perspectives

The general principles in terms of reactivity and stability to design efficient electrocatalysts for the alkaline hydrogen oxidation reaction are reviewed. The performance of catalysts in anion-exchange membrane fuel cells is further discussed.

P–d Orbital coupling in silicon-based dual-atom catalysts for enhanced CO2 reduction: insight into electron regulation of active center and coordination atoms

The CO2RR performance of Si-based DACs was studied, identifying several DACs with enhanced activity for CO2 conversion. The Si atom's pz band, influenced by d-electrons, TM atom radius, and coordination, is the key descriptor for catalytic activity.

Изучение возможности применения фульвовой кислоты для флотационного извлечения ванадия на основе расчёта молекулярных дескрипторов

The relevance of the work lies in the need to process acidic productive solutions containing the valuable component vanadium in the form of vanadyl cations. The object of study in this work is fulvic acid (FulvAc), and the subject is the possibility of its use as a flotation reagent-collector of vanadyl cations. The purpose of the work is to study the possibility of flotation extraction of vanadium from acidic productive solutions. To achieve the goal, the following tasks are set: selection of a selectively acting collecting reagent in relation to a valuable component based on the "structure-property / activity-property" principle; carrying out molecular calculations, including structural, physicochemical and quantum chemical parameters of a new reagent of natural origin - fulvic acids; application of a software package for modeling and visualization of "substrate-reagent" systems; studying the mechanism of interaction between FulvAc molecules and the substrate [VO(H2O)4]2+; implementation of laboratory flotation testing of the collecting reagent. The following special research methods are used in the work: chemical modeling and analysis using The Cambridge Crystallographic Data Center (CCDC) and Avogadro software systems. Calculations of molecular descriptors of flotation activity of a new organic reagent FulvAc in relation to the extractable valuable component vanadium (metal substrate), which quantitatively allow to evaluate the possibility of using FulvAc for flotation extraction of vanadium substrate from solutions based on the principle of "structure-property/activity-property", are presented. The calculation of molecular descriptors carried out in this work has showed that FulvAc due to phenolic, hydroxyl, carbonyl and carboxyl groups are able to form chelate complexes with vanadium cations, oxygen heteroatoms cause chemisorption centers. Vanadium in acidic productive solutions is in the form of vanadyl cations (VO)2+ and aquavanadylcations [VO(H2O)4]2+, which show the properties of complexing agents. Modeling of flotosystems "substrate-reagent" formation with the use of The Cambridge Crystallographic Data Center software is carried out. The possibility of formation of stable substrate-reagent flotation system "(VO)2+ / [VO(H2O)4]2+– FulvAc" by charge-controlled mechanism has been proved.

Theoretical insights into layered IrO2 for the oxygen evolution reaction.

Here we present the density functional theory-based exploration of layered IrO2 polymorphs for the oxygen evolution reaction, as well as a data-driven geometric descriptor for catalytic activity. The layer edges are identified as promising active site motifs with not only low theoretical overpotential but also intriguing structural flexibility and to break the universal energetic scaling through torsional distortion.

Site specific descriptors for oxygen evolution reaction activity on single atom catalysts using QMML

Descriptors are properties or parameters of a material that are used to explain any catalytic activity both computationally and experimentally.