Hydrogenation Of Intermediates Research Articles

Constructing Lewis Acid-Base Pairs to Boost Electrocatalytic Hydrogenation of p-Nitrobenzoic Acid to Valuable p-Aminobenzoic Acid Using Water as the Hydrogen Source.

Electrocatalytic hydrogenation of toxic nitrobenzene to value-added aniline is of great significance in addressing the issues of energy crisis and environmental pollution. However, it is a considerable challenging and crucial to develop highly efficient and earth-abundant transition metal-based electrocatalysts with superior durability for the electro-hydrogenation of nitrobenzene due to the competitive hydrogen evolution reaction (HER). In this work, a facile approach is designed and introduced to constructing an integrated self-supported heterostructured Co1- xNix(OH)(CO3)/Al(OH)3 nanoarrays (CoNiCH/Al(OH)3) for the electrocatalytic reduction of nitrobenzoic acid (PNBA) to p-aminobenzoic acid (PABA) and its electrocatalytic mechanism for PNBA reduction is investigated. This unique Lewis acid-base pairs with abundant oxygen vacancies (OVs) can effectively regulate the adsorption energy of PNBA and active hydrogen intermediates, facilitate the proton-coupled electrocatalytic reduction process, leading to the high activity and selectivity for PNBA to PABA. The optimal CoNiCH/Al(OH)3-0.5 exhibits outstanding performance for the electrocatalytic hydrogenation of PNBA to PABA with a yield of 92%, selectivity of 95% and Faraday efficiency (FE) of 92% at -0.545V (vs reversible hydrogen electrode, RHE) under 0.1m phosphate buffered solution (PBS) neutral electrolyte. Besides, it can maintain a high electrocatalytic activity for at least eight electrocatalytic cycle-test.

A five‐fold twin structure copper for enhanced electrocatalytic nitrogen reduction to sustainable ammonia

AbstractUtilizing N₂ from the air and water for the electrocatalytic nitrogen reduction reaction shows promise for NH₃ synthesis under mild conditions. However, the chemical stability of N₂ and the thermodynamic limitations of NH₃ synthesis hinder its effectiveness. Herein, we integrated a specially designed Cu nanowire catalyst with a five‐fold twin structure (T‐CuNW) into an electrocatalytic system, combining electrocatalytic nitrogen reduction with nonthermal plasma‐assisted N₂ activation. This work achieved an NH₃ yield of 45 mg·mgcat.−1·h−1 and a Faradaic efficiency of over 95% at −0.5 V versus RHE after a 90‐h stability test. In situ characterization revealed that the T‐CuNW's twin structure plays a crucial role for the generation of a large quantity of Hads, essential for the hydrogenation of nitrate intermediates, particularly nitrite (NO₂−). This enhanced hydrogenation process significantly contributes to the high performance of the ammonia synthesis system.

MXene-supported 2D bimetallic chalcogenide electrocatalyst: Enhanced electrochemical seawater splitting

Hydrogen energy holds immense potential for revolutionizing modern energy technologies. Seawater electrolysis is a promising strategy for hydrogen production; however, the lack of effective electrodes limits its widespread application. Therefore, developing high-performance, cost-effective catalysts for water splitting is essential for sustainable energy conversion. In this context, we report a novel hybrid bimetallic selenide (CoMoSe2) and MXene (Ti3C2Tx) electrocatalyst, which exhibits remarkable catalytic performance for seawater electrolysis. The CoMoSe2@Ti3C2Tx electrocatalyst demonstrates outstanding catalytic capabilities, achieving overpotentials of 82 mV for hydrogen evolution reaction (HER) and 329 mV for oxygen evolution reaction (OER) at a current density of 10 mA cm⁻2 in alkaline conditions. The Tafel slope values are 124 mV dec⁻1 for hydrogen evolution and 69 mV dec⁻1 for oxygen evolution, outperforming their individual components. The enhanced bifunctional catalytic performance of the hybrid catalyst is attributed to the synergistic effect of Mo atoms within the CoSe2 crystal structure, which modifies the electronic structure and lowers the chemisorption energies of hydrogen and oxygen intermediates. The abundance of oxygen vacancies provides more reactive active sites and improves electrical conductivity. Additionally, the CoMoSe2@Ti3C2Tx composite has demonstrated remarkable bifunctional electrocatalytic performance for seawater splitting, achieving 10 mA cm⁻2 at overpotentials of 161 mV for HER and 354 mV for OER in alkaline seawater. The Volmer-Heyrovsky mechanism drives the remarkable long-term stability of the catalyst. This novel approach contributes to sustainable energy solutions by providing a fresh avenue for the development of effective catalysts to produce hydrogen from seawater.

Nanoporous nonprecious multi-metal alloys as multisite electrocatalysts for efficient overall water splitting

Developing robust nonprecious metal-based electrocatalysts toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for hydrogen production via electrochemical water splitting. Herein, the NiFeCoCuTi alloy is described as a multisite electrocatalyst for highly effective hydrogen and oxygen evolution in alkaline environments. This is achieved by utilizing heterogeneous atoms on the surface that exhibit distinct adsorption behaviors for hydrogen and hydroxyl, thereby accelerating the dissociation of water and mediating the adsorption of hydrogen intermediates required for molecule formation. The monolithic nanoporous multi-metal NiFeCoCuTi alloy electrode displays remarkable alkaline HER and OER electrocatalysis, exhibiting low overpotentials of 48.7 and 264.2 mV, respectively, to deliver a current density of 10 mA cm−2. Furthermore, it demonstrates exceptional stability for over 100 h in 1 M KOH electrolyte. The exceptional qualities of nanoporous NiFeCoCuTi alloy electrodes make them a highly desirable option for utilization as the cathode and anode material in water electrolysis, which produces hydrogen. They also imply that this is the optimal platform for the development of multisite electrocatalysts.

Constructing Dense CoRu-CoMoO4 Heterointerfaces with Electron Redistribution for Synergistically Boosted Alkaline Electrocatalytic Water Splitting.

Constructing metal alloys/metal oxides heterostructured electrocatalysts with abundant and strongly coupling interfaces is vital yet challenging for practical electrocatalytic water splitting. Herein, CoRu nanoalloys uniformly anchored on CoMoO4 nanosheet heterostructured electrocatalyst (CoRu-CoMoO4/NF) are synthesized via a self-templated strategy by simply annealing of Ru-etched CoMoO4/NF precursor in a reduction atmosphere. The dense and robustly coupled interface not only provides abundant active sites for water splitting but also strengthens the charge transfer efficiency. Furthermore, the theoretical calculations unveil that the strong electronic interaction at CoRu-CoMoO4 interface can induce an interfacial electron redistribution and reduce the energetic barriers for the hydrogen and oxygen intermediates, thereby accelerating the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. The resultant catalyst only requires the overpotentials of 49mV for HER and 209mV for OER at 10mAcm-2. Moreover, the constructed CoRu-CoMoO4||CoRu-CoMoO4 two-electrode cell achieves a cell voltage of 1.54V at 10mAcm-2, outperforming the benchmark Pt/C||IrO2. This work explores an avenue for the rational design of heterostructured electrocatalysts with abundant interfaces for practical water-splitting electrocatalysis.

Unconventional Hexagonal Close-Packed High-Entropy Alloy Surfaces Synergistically Accelerate Alkaline Hydrogen Evolution.

Accelerating the alkaline hydrogen evolution reaction (HER), which involves the slow cleavage of HO-H bonds and the adsorption/desorption of hydrogen (H*) and hydroxyl (OH*) intermediates, requires developing catalysts with optimal binding strengths for these intermediates. Here, the unconventional hexagonal close-packed (HCP) high-entropy alloy (HEA) atomic layers are prepared composed of five platinum-group metals to enhance the alkaline HER synergistically. The breakthrough is made by layer-by-layer heteroepitaxial deposition of subnanometer RuRhPdPtIr HEA layers on the HCP Ru seeds, despite the thermodynamic stability of Rh, Pd, Pt, and Ir in a face-centered cubic (FCC) structure except for Ru. The synchrotron X-ray absorption spectroscopy (XAS) confirms the atomic mixing and coordination environment of HCP RuRhPdPtIr HEA. Most importantly, they exhibit notable improvements in both electrocatalytic activity and durability for the HER in an alkaline environment, as compared to their FCC RuRhPdPtIr counterparts. Electrochemical measurements, operando XAS analysis, and density functional theory unveil that the binding strengths of H* and OH* intermediates on the active Pt and Ir sites can be weakened and strengthened to a moderate level, respectively, by mixing non-active Ru, Rh, and Pd atoms with Pt and Ir atoms within the HCP HEA with strong synergistic electronic effects.

Hydrogen Evolution Reactivity of Pentagonal Carbon Rings and p-d Orbital Hybridization Effect with Ru.

Topological defects are inevitable existence in carbon-based frameworks, but their intrinsic electrocatalytic activity and mechanism remain under-explored. Herein, the hydrogen evolution reaction (HER) of pentagonal carbon-rings is probed by constructing pentagonal ring-rich carbon (PRC), with optimized electronic structures and higher HER activity relative to common hexagonal carbon (HC). Furthermore, to improve the reactivity, we couple Ru clusters with PRC (Ru@PRC) through p-d orbital hybridization between C and Ru atoms, which drives a shortcut transfer of electrons from Ru clusters to pentagonal rings. The electron-deficient Ru species leads to a notable negative shift in d-band centers of Ru and weakens their binding strength with hydrogen intermediates, thus enhancing the HER activity in different pH media. Especially, at a current density of 10 mA cm-2, PRC greatly reduces alkaline HER overpotentials from 540 to 380 mV. And Ru@PRC even exhibits low overpotentials of 28 and 275 mV to reach current densities of 10 and 1000 mA cm-2, respectively. Impressively, the mass activity and price activity of Ru@PRC are 7.83 and 15.7 times higher than that of Pt/C at the overpotential of 50 mV. Our data unveil the positive HER reactivity of pentagonal defects and good application prospects.

Hydrogen Evolution Reactivity of Pentagonal Carbon Rings and p‐d Orbital Hybridization Effect with Ru

AbstractTopological defects are inevitable existence in carbon‐based frameworks, but their intrinsic electrocatalytic activity and mechanism remain under‐explored. Herein, the hydrogen evolution reaction (HER) of pentagonal carbon‐rings is probed by constructing pentagonal ring‐rich carbon (PRC), with optimized electronic structures and higher HER activity relative to common hexagonal carbon (HC). Furthermore, to improve the reactivity, we couple Ru clusters with PRC (Ru@PRC) through p‐d orbital hybridization between C and Ru atoms, which drives a shortcut transfer of electrons from Ru clusters to pentagonal rings. The electron‐deficient Ru species leads to a notable negative shift in d‐band centers of Ru and weakens their binding strength with hydrogen intermediates, thus enhancing the HER activity in different pH media. Especially, at a current density of 10 mA cm−2, PRC greatly reduces alkaline HER overpotentials from 540 to 380 mV. And Ru@PRC even exhibits low overpotentials of 28 and 275 mV to reach current densities of 10 and 1000 mA cm−2, respectively. Impressively, the mass activity and price activity of Ru@PRC are 7.83 and 15.7 times higher than that of Pt/C at the overpotential of 50 mV. Our data unveil the positive HER reactivity of pentagonal defects and good application prospects.

Operando Stable Palladium Hydride Nanoclusters Anchored on Tungsten Carbides Mediate Reverse Hydrogen Spillover for Hydrogen Evolution

AbstractProton exchange membrane (PEM) electrolysis holds great promise for green hydrogen production, but suffering from high loading of platinum‐group metals (PGM) for large‐scale deployment. Anchoring PGM‐based materials on supports can not only improve the atomic utilization of active sites but also enhance the intrinsic activity. However, in practical PEM electrolysis, it is still challenging to mediate hydrogen adsorption/desorption pathways with high coverage of hydrogen intermediates over catalyst surface. Here, operando generated stable palladium (Pd) hydride nanoclusters anchored on tungsten carbide (WCx) supports were constructed for hydrogen evolution in PEM electrolysis. Under PEM operando conditions, hydrogen intercalation induces formation of Pd hydrides (PdHx) featuring weakened hydrogen binding energy (HBE), thus triggering reverse hydrogen spillover from WCx (strong HBE) supports to PdHx sites, which have been evidenced by operando characterizations, electrochemical results and theoretical studies. This PdHx‐WCx material can be directly utilized as cathode electrocatalysts in PEM electrolysis with ultralow Pd loading of 0.022 mg cm−2, delivering the current density of 1 A cm−2 at the cell voltage of ~1.66 V and continuously running for 200 hours without obvious degradation. This innovative strategy via tuning the operando characteristics to mediate reverse hydrogen spillover provide new insights for designing high‐performance supported PGM‐based electrocatalysts.

MXene quantum dots-Co(OH)2 heterojunction stimulated Co2+δ sites for boosted alkaline hydrogen evolution

Persevering structural stability of the active species after phase reconfiguration poses a key challenge for various sustainable catalytic systems. In this study, we construct a robust β-Co(OH)2 electrocatalyst via self-adaptive coordination of MXene quantum dots (MQDs) during phase transition from the Co2(OH)3Cl precursor to β-Co(OH)2 (MQDs/β-Co(OH)2/Co foam). The heterojunction induced the excellent electron transfer, causing the lattice strain of β-Co(OH)2, and the accumulated electrons at the MQDs end regulated the electronic density of Co sites (Co2+δ), reversing the structural instability of β-Co(OH)2 within the applied reduction potential range. Furthermore, density functional theory calculation confirms the role of well-matched heterogeneous interfaces in HER. The result shows the high-valance Co2+δ sites promote adsorption and dissociation of H2O, increasing proton supply and accelerating reaction rate. Concurrently, MQDs facilitate the adsorption of hydrogen intermediates and H2 generation. Our architected catalyst exhibited exceptional alkaline hydrogen evolution reactions (HERs) performance (91 mV@10 mA cm−2) and superior stability outperforms most reported β-Co(OH) 2-based catalysts. Our work demonstrates the efficacy of MQDs as co-catalysts in enhancing the activity and structural stability of catalysts.

Built-in electric field-driven electron transfer behavior at Ru-RuP2 heterointerface fosters efficient and CO-resilient alkaline hydrogen oxidation

Exploiting a cost-effective electrocatalyst for hydrogen oxidation reaction (HOR) with high-performance and CO poisoning resistance is essential for the widespread application of alkaline anion exchange membrane fuel cells (AEMFCs). Herein, we craft a unique Ru-RuP2 heterostructure within hollow mesoporous carbon sphere (Ru-RuP2@C) using phosphide-controlled phase-transition approach. Benefiting from the interfacial electron transfer from RuP2 to Ru, the Ru-RuP2@C electrocatalyst exhibits impressive HOR performance with a mass activity of 2.87 mA μgRu−1. Notably, Ru-RuP2@C demonstrates strong tolerance to 1000 ppm CO, a capability lacking in PtRu/C and Pt/C. When serves as an anode catalyst for AEMFC, it achieves a peak power density of 521 mW cm−2, comparable to Pt/C. Experimental and theoretical analyses reveal that the built-in electric field, resulting from work function differences, creates an asymmetric charge distribution that modulates the d-band center of Ru-RuP2@C. This optimizes the adsorption strength of hydrogen and hydroxide intermediates, thereby accelerating HOR catalytic kinetics.

New Insights for High-Throughput CO2 Hydrogenation to High-Quality Fuel.

In the case of CO2 thermal-catalytic hydrogenation, highly selective olefin generation and subsequent olefin secondary reactions to fuel hydrocarbons in an ultra-short residence time is a huge challenge, especially under industrially feasible conditions. Here, we report a pioneering synthetic process that achieves selective production of high-volume commercial gasoline with the assistance of fast response mechanism. In situ experiments and DFT calculations demonstrate that the designed NaFeGaZr presents exceptional carbiding prowess, and swiftly forms carbides even at extremely brief gas residence times, facilitating olefin production. The created successive hollow zeolite HZSM-5 further reinforces aromatization of olefin diffused from NaFeGaZr via optimized mass transfer in the hollow channel of zeolite. Benefiting from its rapid response mechanism within the multifunctional catalytic system, this catalyst effectively prevents the excessive hydrogenation of intermediates and controls the swift conversion of intermediates into aromatics, even in high-throughput settings. This enables a rapid one-step synthesis of high-quality gasoline-range hydrocarbons without any post-treatment, with high commercial product compatibility and space-time yield up to 0.9 kggasoline ⋅ kgcat -1 ⋅ h-1. These findings from the current work can provide a shed for the preparation of efficient catalysts and in-depth understanding of C1 catalysis in industrial level.

Tuned targeted catalytic engineering enables high-selective electrochemical low-concentration nitrate-to-ammonia

Electrocatalytic nitrate reduction reaction (NO3RR) is anticipated to enable utilization of NO3- from wastewater, providing a prospective solution to address global nitrogen-cycle imbalance. Nevertheless, high-selective conversion of low-concentration NO3--to-NH3 in non-alkaline environment remains challenging, stemming from kinetic retardation and hydrogen evolution reaction (HER). Herein, a targeted synergistic-cascade strategy is proven for breaking through the bottleneck. Significantly, the rationally-designed asymmetric oxygen vacancies (VO)-mediated Cu-Co dual-site catalyst achieve a NH3 selectivity of 95.79 % and a NH3-N yield of 1.528 mg h−1 cm−2 under 140 ppm NO3--N environment. The mitigation of kinetic bottlenecks is attributed to the NO3- activation capability of Cu sites and intermediate hydrogenation of Co sites on the optimized cascade catalytic system. Density functional theory (DFT) reveals that the asymmetric VO fine-tuned the electronic structure and d-band center of Cu-Co dual-sites, which synergistically reduce the energy barrier of NO3RR and alleviate the competing HER. An integrated system is constructed for the in situ conversion of NO3- to ammonium sulfate under low NO3--N concentration water body, showcasing the potential for practical application.

First-Principles Calculations and Machine Learning of Hydrogen Evolution Reaction Activity of Nonmetallic Doped β-Mo2C Support Pt Single-Atom Catalysts.

The most widely used catalyst for the hydrogen evolution reaction (HER) is Pt, but the high cost and low abundance of Pt need to be urgently addressed. Single-atom catalysts (SACs) have been an effective means of improving the utilization of Pt atoms. In this work, we used a nonmetal (NM = B, N, O, F, Si, P, S, Cl, As, Se, Br, Te, and I) doped β-Mo2C (100) C-termination surface as the support, with Pt atoms dispersed on the support surface to construct Pt@NM-Mo2C. Using density functional theory (DFT) calculations, we selected catalysts with excellent HER activity. Among 117 candidate catalysts, 49 catalysts exhibited ideal catalytic performance with Gibbs free energy of hydrogen intermediate (H*) adsorption (ΔGH*) values less than 0.2 eV. The ΔGH* values of 16 catalysts were even lower than that of Pt (ΔGH* ≈ 0.09 eV), with PtI@N2/4-a-Mo2C demonstrating the best performance (ΔGH* = -0.01 eV). Combined with electronic structure analysis, we could understand the impact of charge transfer between Pt and the underlying NM atoms on the strength of the Pt-H bond, thereby promoting HER activity. Using machine learning (ML), we identified that the primary influencing factors of the HER catalytic activity in the Pt@NM-Mo2C system were the Bader charge transfer of Pt (NePt), the d-band center of Pt (εdPt), and the atomic radius of NM (RNM), with NePt having the greatest impact on the HER catalytic activity.

Modulating local coordination structure over single Pt atom to optimize adsorption behavior for high-efficiency photocatalytic H2 production

The development of single-atom photocatalysts featuring precisely defined coordination structure is of great significance for elucidating the correlations between catalytic performances and coordination structures, yet it remains a grand challenge. Herein, the asymmetric/symmetric Pt-Nx moieties in carbon nitride (denoted as Pt-Nx@MCT, x equals to a coordination number of 3 or 4) are elaborately constructed by a coordination structure regulation strategy. The hydrogen production performances of Pt-N3@MCT and Pt-N4@MCT photocatalysts display a relationship with the Pt-N coordination numbers, with Pt-N3@MCT showing a photocatalytic activity (195 μmol h−1) 3 times that of Pt-N4@MCT (65 μmol h−1) and an apparent quantum yield of 34.1 % at 420 nm. The asymmetric Pt-N3 moiety in Pt-N3@MCT acts as electron collector to promote the separation and transfer of charge carriers and to create the higher occupied Pt d orbital, weakening the bond strength between hydrogen intermediates and Pt atomic sites and accelerating hydrogen production reaction kinetics in Pt-N3@MCT.

Lithium ion battery-assisted solar-driven water splitting

Electrocatalytic water splitting is an efficient strategy to substitute traditional fossil fuels with renewable energy H2. However, its scalable implementation, especially outdoors, has been hindered due to the lack of highly efficient and stable electrocatalysts and high-cost external electricity from the power grid. Here, we develop a hybrid nanostructure comprising N-doped carbon nanotube (NCNT) covalent-linked cobalt disulfide nanoparticles (CoS2-NPs) confined in hollow carbon nanocages (h-CoS@NC). As a bifunctional electrocatalyst for overall water splitting, the multi-heterostructure exhibits superior catalytic activities towards both hydrogen and oxygen-containing intermediates. Inspiringly, a two-electrode electrolyzer combined with the multi-heterostructure realizes a current density of 10 mA cm−2 at a low cell voltage of 1.58 V. When employing an anode of lithium ion battery (LIB), the h-CoS@NC delivers a high specific capacity of 1040 mAh g−1 at 0.1 A g−1 and maintains a considerable capacity of 648 mAh g−1, especially at rate of 5 A g−1. Furthermore, a large capacity of 582 mAh g−1 is achieved at 0.1 A g−1 for sodium ion battery. Moreover, theoretical calculations interpret that the enhanced electrochemical activities of h-CoS@NC should be attributed to the interaction between the CoS2 and carbon matrix, which effectively regulates the local electronic structures and weakens water adsorption/dissociation energies. As a proof-of-concept, a self-powered water splitting system integrating solar-charged lithium-ion battery with a water splitting electrolyzer achieves a steady H2 evolution rate at 0.4 A.

In Situ Surfaced Mn-Mn Dimeric Sites Dictate CO Hydrogenation Activity and C2 Selectivity over MnRh Binary Catalysts.

Massive ethanol production has long been a dream of human society. Despite extensive research in past decades, only a few systems have the potential of industrialization: specifically, Mn-promoted Rh (MnRh) binary heterogeneous catalysts were shown to achieve up to 60% C2 oxygenates selectivity in converting syngas (CO/H2) to ethanol. However, the active site of the binary system has remained poorly characterized. Here, large-scale machine-learning global optimization is utilized to identify the most stable Mn phases on Rh metal surfaces under reaction conditions by exploring millions of likely structures. We demonstrate that Mn prefers the subsurface sites of Rh metal surfaces and is able to emerge onto the surface forming MnRh surface alloy once the oxidative O/OH adsorbates are present. Our machine-learning-based transition state exploration further helps to resolve automatedly the whole reaction network, including 74 elementary reactions on various MnRh surface sites, and reveals that the Mn-Mn dimeric site at the monatomic step edge is the true active site for C2 oxygenate formation. The turnover frequency of the C2 product on the Mn-Mn dimeric site at MnRh steps is at least 107 higher than that on pure Rh steps from our microkinetic simulations, with the selectivity to the C2 product being 52% at 523 K. Our results demonstrate the key catalytic role of Mn-Mn dimeric sites in allowing C-O bond cleavage and facilitating the hydrogenation of O-terminating C2 intermediates, and rule out Rh metal by itself as the active site for CO hydrogenation to C2 oxygenates.

Highly efficient hydrogenation of CO2 to heavy hydrocarbons via NaFeGa catalysts

Transforming CO2 into heavy hydrocarbons via thermal catalytic hydrogenation has garnered interest for its potential to address resource shortages and reduce atmospheric CO2. In this research, NaFeGa catalysts enriched with Ga additives were synthesized by the coprecipitation method. Various characterization techniques, including Mössbauer spectroscopy, were employed alongside reverse water-gas shift and Fischer-Tropsch synthesis experiments to elucidate the Fe-Ga interaction. This interaction effectively modulated the ratio of active sites Fe5C2 and enhanced CO species adsorption. The Ga additive's anti-hydrogenation effect limited intermediate hydrogenation, leading to increased carbon-hydrogen product yields. The catalyst underwent direct hydrogenation of CO2 under high throughput conditions (space velocity of 50,000 h−1), resulting in efficient CO2 conversion as well as remarkable heavy hydrocarbon selectivity. The catalyst demonstrated a remarkable heavy hydrocarbon space-time yield (STY) of 1460.2 g·kgcat−1·h−1, surpassing the threshold for commercial viability and offering a promising solution for large-scale production of liquid fuels from CO2.

Factors Affecting the Formation and Transformation of the Intermediates in Pd(II)-Catalyzed Aromatic C-H Activation: A Comprehensive Study with the Pd(II)/LA Platform.

How the factors affecting the formation and transformation of the intermediates in Pd(II)-catalyzed aromatic C-H activation: A comprehensive study with the Pd(II)/LA platform. Using the Pd(II)/Lewis acid (LA)-catalyzed C-H activation of electron-rich acetanilides as a platform, the C-H activation intermediates, including the precomplex η2-intermediate, the agostic hydrogen intermediate, and the palladacycle compound have been well-characterized. This work presents how the catalyst source, substrate, and solvent affect the formation of the η2-intermediate and its equilibrium with the agostic hydrogen intermediate, and the transformation of the agostic hydrogen intermediate to the palladacycle compound through C-H activation. The findings disclosed above are provided as a guideline for the catalyst design of the oxidative olefination of acetanilide with dioxygen, and the catalytic efficiency matched well with the mechanistic findings.

Rhenium-promoter-free ruthenium–zirconia catalyst for high-yield direct conversion of succinic acid to 1,4-butanediol in water

The direct conversion of succinic acid to 1,4-butanediol (1,4-BDO) in water was investigated using Ru deposited on oxygen-vacant zirconia (Ru–OvZrOx) as the catalyst. 1,4-BDO was produced in high yield (89.5 %) and space–time yield (0.19 h−1) at 200 °C. The proximity of Ru to OvZrOx stabilized the nanosized Ru0 particles, enabled hydrogen spillover, increased the acidity of the catalyst, and achieved intermediate adsorption. The Zrδ+ center (2 ≤ δ < 4)—which featured abundant Lewis acid sites and was adjacent to the Ov sites—activated the γ-butyrolactone ring-opening reaction via a route involving 2-hydroxytetrahydrofuran formation. The electron-rich Ru0 center facilitated heterolytic hydrogen dissociation, and the dissociated H– and H+ ions traveled to the Zrδ+ sites and water molecules via hydrogen-shuttling mechanism. Moreover, the weakly bonded hydrogen actively participated in the hydrodeoxygenation and hydrogenation of intermediates to 1,4-BDO.