Reaction Kinetics Research Articles

Facile Synthesis of Rhodium-Based Nanocrystals in a Metastable Phase and Evaluation of Their Thermal and Catalytic Properties.

Controlling the polymorphism of metal nanocrystals is a promising strategy for enhancing properties and discovering new phenomena. However, previous studies on Rh nanocrystals have focused on their thermodynamically stable face-centered-cubic (fcc) phase. Herein, a facile synthesis of Rh-based nanocrystals featuring the metastable hexagonal close-packed (hcp) phase is reported by using Ru seeds in their native hcp phase to template the deposition of Rh atoms. The success of such phase-controlled synthesis relies on the templating effect promoted by the small lattice mismatch between Ru and Rh and the slow dropwise titration of the precursor at an elevated temperature, ensuring the layer-by-layer growth mode and thus the formation of a conformal hcp-Rh shell. Faster injection rate of Rh(III) precursor leads to the formation of a rough Rh shell in the conventional fcc phase due to accelerated reaction kinetics. Considering both thermodynamic and kinetic aspects of this system, the hcp-Rh phase is favored when the low surface energy from smooth overlayers balances the high bulk energy of the metastable phase, achieved through tight control of reaction rates and deposition patterns. These Ruhcp@Rhhcp core-shell nanocrystals demonstrate thermal stability up to 400°C, while exhibiting higher catalytic activity toward ethanol oxidation reaction compared to Ruhcp@Rhfcc counterparts.

Optimizing Aqueous Zinc-Sulfur Battery Performance via Regulating Acetonitrile Co-Solvents and Carbon Nanotube Carriers.

Rechargeable aqueous zinc-sulfur batteries (AZSBs) are gaining attention due to their high energy density, ultra-stable discharge platform, and safety. However, poor liquid/solid reaction processes at the anode and cathode reduce reaction kinetics, and the severe dissolution of polysulfides causes shuttle effects during discharge/charge cycles, hindering practical applications. Improving performance requires optimizing both the cathode and electrolyte. Herein, we design an organic-inorganic hybrid electrolyte (zinc trifluoromethanesulfonate and trace iodine monomer dissolved in an acetonitrile/water co-solvent (AN-X)) and a partially exfoliated multi-walled carbon nanotube (PECNT) hosted sulfur (S@PECNTs) cathode for AZSBs. The sulfur is highly dispersed along the PECNTs with appropriate wettability at the electrode/electrolyte interface using AN-3 as the electrolyte. Meanwhile, this electrolyte inhibits hydrogen evolution at negative potentials and promotes uniform Zn ion stripping/plating. Expressively, the AN-3-based AZSB exhibits a high discharge capacity of 1370 mAh g-1 with excellent Coulombic efficiency (79.9%), outstanding rate capability, and cycling performance. These improvements are attributed to the synergistic effect between the S@PECNTs and the AN-3 electrolyte, which reduces Rct to enhance reaction kinetics and blocks the dissolution and shuttle effect of polysulfides, ensuring a reversible reaction between zinc and sulfur.

Investigation on the Necessity of Low Rates Activation toward Lithium‐Sulfur Batteries

AbstractLow rate activation process is always used in conventional transition metal oxide cathode and fully activates active substances/electrolyte to achieve stable electrochemical performance. However, the related working mechanism in lithium‐sulfur (Li‐ battery is unclear due to the multiple complex chemical reaction steps including the redox of sulfur and the dissolution of polysulfides intermediate. Hence, the influencing mechanism of activation process on Li‐S battery is explored by adopting different current densities of 0.05, 0.2, and 1 C in initial three cycles before long‐term cycling tests at 0.2 C (denoted by 0.05, 0.2, and 1‐battery). 0.05‐battery presents the highest initial capacity in activation process, while 0.2‐battery presents superior electrochemical performances after 150 cycles. The similar trend can be found in more long‐term cycling rates such as 0.02, 0.1, 0.5, and 1 C. Potentiostatically Li2S precipitation test demonstrates that rapid generation of Li2S is achieved at higher current density, and S8‐Li2Sn‐Li2S conversion is accelerated according to Tafel plots. However, interfacial electrochemical and physical characterizations suggest that serious lithium dendrite growth will be induced under high current density. Therefore, considering the reaction kinetics and interfacial properties, low rate activation process is unnecessary when cycling current lower than 1 C for Li‐S battery.

Porous Carbon‐supported Catalysts for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are crucial for the efficient utilization of hydrogen. Currently, their efficiency is mainly limited by the slow kinetics of the cathode oxygen reduction reaction (ORR) and the poisoning effect between ionomers and catalytic sites, particularly with Pt‐based catalysts. Recent works suggest that the emerging porous carbon‐supported catalysts hold promise in mitigating these challenges by ensuring fast kinetics while alleviating the poisoning. This review examines porous carbon‐supported catalysts for PEMFC cathodes, covering synthesis methods, structure and performance evaluation, and future prospects, with an emphasis on the influence of porous carbon support on PEMFC performance. On one hand, the rational design of pore structure in carbon support can help optimize the location of the active sites and enhance mass transfer. On the other hand, diverse pore structures provide a platform for gaining a deeper understanding of the mechanisms behind micro‐scale mass transfer and reaction at the three‐phase boundaries. This review aims to inspire innovative strategies for the precise synthesis of porous carbon‐supported catalysts with various pore structures to further boost PEMFC performance.

Proton exchange membrane‐based electrocatalytic systems for hydrogen production

AbstractHydrogen energy from electrocatalysis driven by sustainable energy has emerged as a solution against the background of carbon neutrality. Proton exchange membrane (PEM)‐based electrocatalytic systems represent a promising technology for hydrogen production, which is equipped to combine efficiently with intermittent electricity from renewable energy sources. In this review, PEM‐based electrocatalytic systems for H2 production are summarized systematically from low to high operating temperature systems. When the operating temperature is below 130°C, the representative device is a PEM water electrolyzer; its core components and respective functions, research status, and design strategies of key materials especially in electrocatalysts are presented and discussed. However, strong acidity, highly oxidative operating conditions, and the sluggish kinetics of the anode reaction of PEM water electrolyzers have limited their further development and shifted our attention to higher operating temperature PEM systems. Increasing the temperature of PEM‐based electrocatalytic systems can cause an increase in current density, accelerate reaction kinetics and gas transport and reduce the ohmic value, activation losses, ΔGH*, and power consumption. Moreover, further increasing the operating temperature (120–300°C) of PEM‐based devices endows various hydrogen carriers (e.g., methanol, ethanol, and ammonia) with electrolysis, offering a new opportunity to produce hydrogen using PEM‐based electrocatalytic systems. Finally, several future directions and prospects for developing PEM‐based electrocatalytic systems for H2 production are proposed through devoting more efforts to the key components of devices and reduction of costs.

Enhancing Oxygen Reduction Kinetics and Proton Transfer of La0.6Sr0.4Co0.2Fe0.8O3−δ Cathode through Pr2Ni0.5Co0.5O4−δ Impregnation for Protonic Ceramic Fuel Cells

AbstractSluggish reaction kinetics in oxygen reduction reaction (ORR) is one of the most important challenges to the development of protonic ceramic fuel cells (PCFCs). La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) exhibits high mixed ionic–electronic conductivity in traditional solid oxide fuel cells, but their slow proton transfer and ORR kinetics impedes practical applications. Herein, composite Pr2Ni0.5Co0.5O4−δ (PNC) particles composed of a perovskite PrNi0.5Co0.5O3−δ phase and a PrO2 phase are impregnated into a LSCF cathode to enhance the ORR activity and proton transfer. The polarization tested in a symmetric cell with PNC‐impregnated LSCF cathode is 0.06 Ω cm2 at 700 °C. The fuel cell with this impregnated cathode shows maximum power densities of 1857 mW cm−2 at 700 °C. Moreover, the impregnated cathode exhibits a low degradation rate in the durability test. This work not only provides a novel and practical approach to improving the performance of current cathode materials for PCFCs but also highlights the potential for enhancing the commercial viability of PCFC technology.

Enzyme catalytic efficiency prediction: employing convolutional neural networks and XGBoost

IntroductionIn the intricate realm of enzymology, the precise quantification of enzyme efficiency, epitomized by the turnover number (kcat), is a paramount yet elusive objective. Existing methodologies, though sophisticated, often grapple with the inherent stochasticity and multifaceted nature of enzymatic reactions. Thus, there arises a necessity to explore avant-garde computational paradigms.MethodsIn this context, we introduce “enzyme catalytic efficiency prediction (ECEP),” leveraging advanced deep learning techniques to enhance the previous implementation, TurNuP, for predicting the enzyme catalase kcat. Our approach significantly outperforms prior methodologies, incorporating new features derived from enzyme sequences and chemical reaction dynamics. Through ECEP, we unravel the intricate enzyme-substrate interactions, capturing the nuanced interplay of molecular determinants.ResultsPreliminary assessments, compared against established models like TurNuP and DLKcat, underscore the superior predictive capabilities of ECEP, marking a pivotal shift in silico enzymatic turnover number estimation. This study enriches the computational toolkit available to enzymologists and lays the groundwork for future explorations in the burgeoning field of bioinformatics. This paper suggested a multi-feature ensemble deep learning-based approach to predict enzyme kinetic parameters using an ensemble convolution neural network and XGBoost by calculating weighted-average of each feature-based model’s output to outperform traditional machine learning methods. The proposed “ECEP” model significantly outperformed existing methodologies, achieving a mean squared error (MSE) reduction of 0.35 from 0.81 to 0.46 and R-squared score from 0.44 to 0.54, thereby demonstrating its superior accuracy and effectiveness in enzyme catalytic efficiency prediction.DiscussionThis improvement underscores the model’s potential to enhance the field of bioinformatics, setting a new benchmark for performance.

Low-dimensional projection of reactivity classes in chemical reaction dynamics using supervised dimensionality reduction.

Transition state theory (TST) provides a framework to estimate the rate of chemical reactions. Despite its great success with many reaction systems, the underlying assumptions such as local equilibrium and nonrecrossing do not necessarily hold in all cases. Although dynamical systems theory can provide the mathematical foundation of reaction tubes existing in phase space that enables us to predict the fate of reactions free from the assumptions of TST, numerical demonstrations for large systems have been yet one of the challenges. Here, we propose a dimensionality reduction algorithm to demonstrate structures in phase space (called reactive islands) that predict reactivity in systems with many degrees of freedom. The core of this method is the application of supervised principal component analysis, where a coordinate transformation is performed to preserve the dynamical information on reactivity (i.e., to which potential basin the system moves from a region of interest) as much as possible. The reactive island structures are expected to be reflected in the transformed, low-dimensional phase space. As an illustrative example, the algorithm is scrutinized using a modified Hénon-Heiles Hamiltonian system extended to many degrees of freedom, which has three channels leading to three different products from one stable potential basin. It is shown that our algorithm can predict the reactivity in the transformed, low-dimensional coordinate system better than a naïve coordinate system and that the reactivity distribution in the transformed low-dimensional space is considered to reflect the underlying reactive islands.

In Situ Synthesis of MoO 3 by Surface Oxidation of Mo 2 C (MXene) for Stable Near‐Surface Reactions in Aqueous Aluminum‐Ion Battery

Molybdenum trioxide (MoO3) is a promising positive electrode material for aqueous aluminum‐ion batteries due to its high theoretical capacity. However, MoO3 faces several challenges in an aqueous electrolyte, such as easy dissolution of reaction products, volume expansion, and low conductivity, which severely limit its application in aqueous batteries. In this work, we effectively increased the overall conductivity of the electrode by in‐situ growing MoO3 on the Mo2C MXene layer. MXene can effectively inhibit the dissolution and structural loss of MoO3 reaction products. Additionally, the coordination effect of Mo2C and MoO3 achieves a stable near‐surface reaction on the MXene laminates, resulting in the Mo2C/MoO3 composite exhibiting excellent aluminum storage properties (123.5 mAh/g after 200 cycles at 0.4 A/g). The energy storage mechanism of H+/Al3+ co‐insertion/extraction was elucidated through non‐in‐situ characterization, and the promotion effect of Mo2C on MoO3 reaction kinetics was verified by density functional theory calculations. This work provides new insights into improving the stability of AAIB cathodes and extends the application of Mo‐based MXene in aqueous batteries.

Nocturnal atmospheric synergistic oxidation reduces the formation of low-volatility organic compounds from biogenic emissions

Abstract. Volatile organic compounds (VOCs) are often subject to synergistic oxidation by different oxidants in the atmosphere. However, the exact synergistic-oxidation mechanism of atmospheric VOCs and its role in particle formation remain poorly understood. In particular, the reaction kinetics of the key reactive intermediates, organic peroxy radicals (RO2), during synergistic oxidation is rarely studied. Here, we conducted a combined experimental and kinetic modeling study of the nocturnal synergistic oxidation of α-pinene (the most abundant monoterpene) by O3 and NO3 radicals as well as its influences on the formation of highly oxygenated organic molecules (HOMs) and particles. We find that in the synergistic O3 + NO3 regime, where OH radicals are abundantly formed via decomposition of ozonolysis-derived Criegee intermediates, the production of CxHyOz HOMs is substantially suppressed compared to that in the O3-only regime, mainly because of the depletion of α-pinene RO2 derived from ozonolysis and OH oxidation by those arising from NO3 oxidation via cross reactions. Measurement–model comparisons further reveal that the cross-reaction rate constants of NO3-derived RO2 with O3-derived RO2 are on average 10–100 times larger than those of NO3-derived RO2 with OH-derived RO2. Despite a strong production of organic nitrates in the synergistic-oxidation regime, the substantial decrease in CxHyOz HOM formation leads to a significant reduction in ultralow- and extremely low-volatility organic compounds, which significantly inhibits the formation of new particles. This work provides valuable mechanistic and quantitative insights into the nocturnal synergistic-oxidation chemistry of biogenic emissions and will help to better understand the formation of low-volatility organic compounds and particles in the atmosphere.

Improving the Electrocatalytic Activity of a Core/Shell NiCo-ZIF@PBA Catalyst by Co-O-Fe Bridge Bonds for Water Oxidation.

In response to the limitations of slow reaction kinetics and elevated overpotentials in the OER, a novel core-shell structured electrocatalyst, termed NiCo-ZIF-67@Fe-Co-Ni-PBA or NiCo-ZIF@PBA, has been developed. This material demonstrates exceptional catalytic performance, exhibiting a minimal overpotential of approximately 188 mV at 10 mA cm-2, alongside a Tafel slope of 109 mV dec-1. Its robust stability in a 1 M KOH solution during the OER operations is noteworthy. Theoretical insights from DFT calculations reveal that a Co-O-Fe bridging configuration within NiCo-ZIF@PBA lowers the energy barrier for the reaction to 1.79 eV, a significant reduction from 2.67 eV observed with NiCo-ZIF-67. The improvement in electrochemical performance is primarily due to the emergence of Co3+ ions, which results from the efficient charge transfer occurring at the interface of the PBA and NiCo-ZIF core-shell structure. These findings suggest a promising strategy for designing advanced core-shell materials for electrocatalytic applications.

Nitrogen-Doped Graphene Uniformly Loaded with Large Interlayer Spacing MoS2 Nanoflowers for Enhanced Lithium–Sulfur Battery Performance

Lithium–sulfur (Li-S) batteries offer a high theoretical energy density but suffer from poor cycling stability and polysulfide shuttling, which limits their practical application. To address these challenges, we developed a PANI-modified MoS2-NG composite, where MoS2 nanoflowers were uniformly grown on graphene oxide (GO) through PANI modification, resulting in an increased interlayer spacing of MoS2. This expanded spacing exposed more active sites, enhancing polysulfide adsorption and catalytic conversion. The composite was used to prepare MoS2-NG/PP separators for Li-S batteries, which achieved a high specific capacity of 714 mAh g−1 at a 3 C rate and maintained a low capacity decay rate of 0.085% per cycle after 500 cycles at 0.5 C. The larger MoS2 interlayer spacing was key to improving redox reaction kinetics and suppressing the shuttle effect, making the MoS2-NG composite a promising material for enhancing the performance and stability of Li-S batteries.

Pd-Co Supported on Anodized Aluminium for VOCs Abatement: Reaction Mechanism, Kinetics and Applicability as Monolithic Catalyst

It has been found out that Pd-Co-based catalyst, supported on anodized aluminum, possesses very high activity in combustion reactions of C1–C6 alkanes and toluene. The catalyst characterization has been made by N2-pysisorption, XRD, SEM, XPS, FTIR, TEM, and EPR methods. In view of the great interest, methane combustion was investigated in detail. It is ascertained that the complete oxidation of methane proceeds by dissociative adsorption on PdO and formation of hydroxyl and methyl groups, the former being highly reactive, and it undergoes further reaction to oxygen-containing intermediates, whereupon HCHO is one of them. The presence of Co2+ cations promotes greatly oxygen adsorption. The dissociative adsorption is favored on neighboring Co2+ cations, leading to the formation of bridging peroxides. Further, the oxygen dissociates on the nearest Pd2+ cations. According to the results from the experimental data, instrumental methods, and the observed kinetics and DFT model calculations, it can be concluded that the reaction pathway over Pd+Co/anodic alumina support (AAS) catalyst proceeds most probably through Mars–van Krevelen. The obtained data on the kinetics were used for simulation of the methane combustion in a full-scale adiabatic reactor.

Strategically Modified Ligand Incorporating Mixed Phosphonate and Carboxylate Groups to Enhance Performance in All‐Iron Redox Flow Batteries

AbstractIron redox flow batteries (Fe‐RFBs) hold significant promise for achieving cost‐effectiveness and utilizing abundant materials for stationary energy storage applications. Here, a design of a novel Fe complex utilizing a nitrogenous phosphonate/carboxylate mixed ligand, N,N‐Bis(phosphonomethyl)glycine (BMPG), is presented to achieve high performance Fe anolyte. Compared to its all‐phosphonate form, nitrilotri(methylphosphonic acid) (NTMPA), the new complex Fe(BPMG)2 demonstrates a negatively shifted redox potential, resulting in ≈0.07 V (≈10%) increase in battery output voltage. Full battery testing paired with ferrocyanide catholyte demonstrates stable cycling (capacity degradation <0.0001%/cycle) over 730 consecutive charge/discharge cycles with Coulombic Efficiency of 100% at a current density of 20 mA cm−2 under near neutral pH (≈8). Of particular interest, density functional theory (DFT) studies and operando Raman measurements provide strong evidence supporting a molecular structure in BPMG, which reveals the mixed phosphonate/carboxylate groups in BPMG maintain the octahedral coordination of the Fe ion center with phosphonates exclusively, while leaving the carboxylate unbound for both Fe(II) and Fe(III) complexes. This structural similarity between BPMG‐based Fe(II) and Fe(III) complexes effectively mitigates the slow redox reaction kinetics observed in Fe(NTMPA)2 anolyte, where significant ligand reorientation occurs between Fe(II) and Fe(III) complexes.

Multifunctional Strategies of Advanced Electrocatalysts for Efficient Urea Synthesis.

The electrochemical reduction of nitrogenous species (such as N2, NO, NO2 -, and NO3 -) for urea synthesis under ambient conditions has been extensively studied due to their potential to realize carbon/nitrogen neutrality and mitigate environmental pollution, as well as provide a means to store renewable electricity generated from intermittent sources such as wind and solar power. However, the sluggish reaction kinetics and the scarcity of active sites on electrocatalysts have significantly hindered the advancement of their practical applications. Multifunctional engineering of electrocatalysts has been rationally designed and investigated to adjust their electronic structures, increase the density of active sites, and optimize the binding energies to enhance electrocatalytic performance. Here, surface engineering, defect engineering, doping engineering, and heterostructure engineering strategies for efficient nitrogen electro-reduction are comprehensively summarized. The role of each element in engineered electrocatalysts is elucidated at the atomic level, revealing the intrinsic active site, and understanding the relationship between atomic structure and catalytic performance. This review highlights the state-of-the-art progress of electrocatalytic reactions of waste nitrogenous species into urea. Moreover, this review outlines the challenges and opportunities for urea synthesis and aims to facilitate further research into the development of advanced electrocatalysts for a sustainable future.

Interrogating the Role of Stack Pressure in Transport‐Reaction Interaction in the Solid‐State Battery Cathode

AbstractAs solid‐state batteries (SSBs) emerge as leading contenders for next‐generation energy storage, chemo‐mechanical challenges and instabilities at solid‐solid interfaces remain a critical bottleneck. Ensuring sufficient interfacial contact within composite cathode architectures often requires the application of high stack pressures, posing a significant hurdle in the development of viable, large‐scale SSBs. In this work, the impact of stack pressure is investigated on the performance of solid‐state composite cathodes comprised of single‐crystal LiNi0.5Mn0.3Co0.2O2 (SC‐NMC532) active material particles and a Li6PS5Cl (LPSCl) solid electrolyte phase. By unraveling the complex interplay between stack pressure and microstructure‐dependent mechanisms, the profound influence on interfacial resistances, cathode utilization dynamics, current constriction effects, and lithiation heterogeneities are revealed. Through a comprehensive examination of coupled reaction kinetics and transport interactions at the electrode and particle length scales, the implications of stack pressure at different C‐rates and microstructural arrangements are elucidated, thereby delineating the limiting mechanisms that are prevalent at low stack pressures. This work underscores the critical role of optimizing the cathode microstructure to mitigate the chemo‐mechanical challenges associated with SSB operation at low stack pressures, offering valuable insights and design guidelines for the development of high‐performance SSBs.

UIO-66-NH2 as Photo-Assisted Li-O2 Battery Cathode for High-Current Discharge.

Li-O2 batteries (LOBs) have garnered significant attention in recent years due to high theoretical specific capacity, however, the sluggish charge-discharge reaction kinetics and rapid failure under high current densities have hindered their further application. This work presents a photo-responsive catalyst (UIO-66-NH2) supported on carbon cloth, which could enhance the reaction kinetics of LOBs and improve the discharge capacity under high current densities. It demonstrates that under light, the overpotential decreases by 0.9 V, and the discharge capacity reaches an impressive 4.8 mAh cm-2 at a current density of 0.5 mA cm-2. This finding is expected to inspire the development of various novel MOF-based photoelectrodes for LOBs.

Glutaraldehyde Cross-Linking of Salt-Induced Fibrinogen Hydrogels.

Covalent cross-linking is a common strategy to improve the mechanical properties of biological polymers. The most prominent field of application of such materials is in medicine, for example, in the form of bioprinting, drug delivery, and wound sealants. One biological polymer of particular interest is the blood clotting protein fibrinogen. In the natural process, fibrinogen polymerizes to fibrous hydrogel fibrin. Although the material shows great potential, its costs are very high due to the required enzyme thrombin. Recently, we introduced several approaches to trigger a thrombin-free fibrillogenesis of fibrinogen to a fibrin-like material. Inspired by the natural pathway of blood clotting in which covalent cross-linking stabilizes the clot, this "pseudofibrin" is now developed even further by covalently cross-linking the fibers. In particular, the effect of inexpensive glutaraldehyde on fiber morphology, rheological properties, and irreversible gel dissolution is investigated. Additionally, new insights into the reaction kinetics between fibrinogen and glutaraldehyde are gained. It could be shown that the fibrous structure of pseudofibrin can be retained during cross-linking and that glutaraldehyde significantly improves rheological properties of the hydrogels. Even more important, cross-linking with glutaraldehyde can prevent dissolution of the gels at elevated temperatures.

Mass Transportation Facilitated Porous Fe/Co Dual‐Site Catalytic Cathodes for Ultrahigh‐Power‐Density Al–Air Fuel Cells

AbstractThe development of oxygen‐dependent fuel cells is frequently hindered by the high cost of cathode materials and the sluggish kinetics of the oxygen reduction reaction (ORR). It is thus crucial to explore low‐cost and high‐activity catalysts with accelerated mass transport. Here, a high‐throughput screening method is developed by integrating an explicit solvation model with machine learning potential‐based molecular dynamics simulations, which enables the efficient evaluation of a vast array of diverse diatomic combinations and ultimately identifying Fe–Co dual‐atomic sites as the optimal ORR electrocatalysts. The superior electrocatalytic performance of the diatomic Fe/Co sites loaded on 3D‐interconnected ordered macroporous carbon (FeCo‐3DMNC) is experimentally verified, achieving high ORR activity with half‐wave potentials of 0.806 V in acidic and 0.905 V in alkaline environments. Additionally, innovative hybrid acid/alkali aluminum–air fuel cells (hA/A‐AAFCs) incorporating FeCo‐3DMNC as the cathode catalyst demonstrate a notably high open‐circuit voltage of 2.72 V and a record‐breaking power density of 827 mW cm−2, significantly outperforming conventional alkaline aluminum–air fuel cells. This work marks a significant advancement by combining cutting‐edge computational screening with rigorous experimental validation to develop promising electrocatalysts, potentially paving the way for the advanced energy storage and conversion technologies.

Cu-Promoted ipso-Hydroxylation of sp2 Bonds with Concomitant Aromatic 1,2-Rearrangement Involving a Cu-oxyl-hydroxo Species.

Herein, we report the first example of Cu-promoted β ipso-hydroxylation of substituted benzophenones using a bidentate directing group (DG) and H2O2 as an oxidant. In addition to the new C-O bond formed, the ipso-oxidation induces a very unusual 1,2-rearrangement of the iminyl group to the vicinal γ position. This transformation is highly dependent on the substrate utilized (favored for 4-methoxy-substituted benzophenones) and on the DG used (2-picolylamine leads to selective γ-C-H functionalization, while β ipso-oxidation requires 2-(2-aminoethyl)pyridine). An analysis of the oxidation of substrate-ligands derived from 2-(2-aminoethyl)pyridine and unsymmetrical 4-MeO-substituted benzophenones indicates high regioselectivity (up to 89:11 for the MeO-substituted arene ring and up to 92:8 for β ipso- vs γ-C-H hydroxylation). Mechanistic studies (which include spectroscopic characterization of reaction intermediates, kinetics, and calculations) suggest the formation of a mononuclear CuIIOOH species before the rate-determining step (rds) of the reaction. DFT calculations suggest that the γ-C-H hydroxylation pathway involves a one-step concerted O-O cleavage and electrophilic aromatic attack. Conversely, β ipso-hydroxylation occurs in a stepwise fashion, in which O-O bond cleavage produces a CuIII(O·)(OH) before electrophilic aromatic attack. Calculations also shed light on the mechanism of the 1,2-rearrangement step, which involves strain release from a spiro 5-membered to a 6-membered Cu chelate.