Activity For Oxidation Reaction Research Articles

An all-metallic nanovesicle for hydrogen oxidation.

Vesicle, a microscopic unit that encloses a volume with an ultrathin wall, is ubiquitous in biomaterials. However, it remains a huge challenge to create its inorganic metal-based artificial counterparts. Here, inspired by the formation of biological vesicles, we proposed a novel biomimetic strategy of curling the ultrathin nanosheets into nanovesicles, which was driven by the interfacial strain. Trapped by the interfacial strain between the initially formed substrate Rh layer and subsequently formed RhRu overlayer, the nanosheet begins to deform in order to release a certain amount of strain. Density functional theory (DFT) calculations reveal that the Ru atoms make the curling of nanosheets more favorable in thermodynamics applications. Owing to the unique vesicular structure, the RhRu nanovesicles/C displays excellent hydrogen oxidation reaction (HOR) activity and stability, which has been proven by both experiments and DFT calculations. Specifically, the HOR mass activity of RhRu nanovesicles/C are 7.52 A mg(Rh+Ru)-1 at an overpotential of 50mV at the rotating disk electrode (RDE) level; this is 24.19 times that of commercial Pt/C (0.31mA mgPt-1). Moreover, the hydroxide exchange membrane fuel cell (HEMFC) with RhRu nanovesicles/C displays a peak power density of 1.62W cm-2 in the H2-O2 condition, much better than that of commercial Pt/C (1.18W cm-2). This work creates a new biomimetic strategy to synthesize inorganic nanomaterials, paving a pathway for designing catalytic reactors.

Pt nanorods supported on Nb-doped ceria: A promising anode catalyst for polymer electrolyte fuel cells

For polymer electrolyte fuel cells (PEFCs), platinum nanoparticles supported on carbon black (Pt/C) serve as the commonly used hydrogen anode catalyst, exhibiting high activity for the hydrogen oxidation reaction (HOR), while the carbon support is susceptible to corrosion under PEFC operation. Here, a highly active HOR anode catalyst of Pt nanorod supported on niobium (Nb)-doped ceria without using corrosive carbon support was developed, which exhibits high durability at high potentials associated with hydrogen starvation. The production of hydrogen peroxide (H2O2), which can degrade the polymer electrolyte membrane, was also found to be significantly suppressed on the Pt nanorod/doped ceria catalyst. Density functional theory (DFT) calculations suggests that the Pt nanorod geometry and interaction with Nb and Ce favor HOR activity and stability while suppressing H2O2 production by modulating the adsorption of key reaction intermediates. This new catalyst has the potential to be used as an anode for high-performance and high-durability PEFCs.

One-step constructing advanced N-doped carbon@metal nitride as ultra-stable electrocatalysts via urea plasma under room temperature

Highly active transition metal nitrides are desirable for electrocatalytic reactions, but their long-term stability is still unsatisfactory and thus limiting commercial applications. Herein, for the first time, we report a unique and universal room-temperature urea plasma method for controllable synthesis of N-doped carbon coated metal (Fe, Co, Ni, etc.) nitrides arrays electrocatalysts. The preformed metal oxides arrays can be successfully converted into metal nitrides arrays with preserved nanostructures and a thin layer of N-doped carbon (NC) via one-step urea plasma. Typically, as a representative case, NC@CoN nanowire arrays are illustrated and corresponding formation mechanism by plasma is proposed. Notably, the designed NC@CoN catalysts deliver excellent electrocatalytic activity and long-term stability both in oxygen evolution reaction (OER) and urea oxidation reaction (UOR). For OER, a low overpotential (264 mV at 10 mA/cm2) and high stability (>50 h at 20 mA/cm2) are acquired. For UOR, a current density of 100 mA/cm2 is achieved at only 1.39 V and maintain over 100 h. Theoretical calculations reveal that the synergetic coupling effect of CoN and NC can significantly facilitate the charge-transfer process, optimize adsorbed intermediates binding strength and further greatly decrease the energy barrier. This strategy provides a novel method for fabrication of NC@ metal nitrides as highly active and stable catalysts.

A High-Performance and Durable Direct-Ammonia Symmetrical Solid Oxide Fuel Cell with Nano La0.6Sr0.4Fe0.7Ni0.2Mo0.1O3-δ-Decorated Doped Ceria Electrode.

Solid oxide fuel cells (SOFCs) offer a significant advantage over other fuel cells in terms of flexibility in the choice of fuel. Ammonia stands out as an excellent fuel choice for SOFCs due to its easy transportation and storage, carbon-free nature and mature synthesis technology. For direct-ammonia SOFCs (DA-SOFCs), the development of anode catalysts that have efficient catalytic activity for both NH3 decomposition and H2 oxidation reactions is of great significance. Herein, we develop a Mo-doped La0.6Sr0.4Fe0.8Ni0.2O3-δ (La0.6Sr0.4Fe0.7Ni0.2Mo0.1O3-δ, LSFNM) material, and explore its potential as a symmetrical electrode for DA-SOFCs. After reduction, the main cubic perovskite phase of LSFNM remained unchanged, but some FeNi3 alloy nanoparticles and a small amount of SrLaFeO4 oxide phase were generated. Such reduced LSFNM exhibits excellent catalytic activity for ammonia decomposition due to the presence of FeNi3 alloy nanoparticles, ensuring that it can be used as an anode for DA-SOFCs. In addition, LSFNM shows high oxygen reduction reactivity, indicating that it can also be a cathode for DA-SOFCs. Consequently, a direct-ammonia symmetrical SOFC (DA-SSOFC) with the LSFNM-infiltrated doped ceria (LSFNM-SDCi) electrode delivers a superior peak power density (PPD) of 487 mW cm-2 at 800 °C when NH3 fuel is utilised. More importantly, because Mo doping greatly enhances the reduction stability of the material, the DA-SSOFC with the LSFN-MSDCi electrode exhibits strong operational stability without significant degradation for over 400 h at 700 °C.

High Entropy Alloys Enable Durable and Efficient Lithium-Mediated CO2 Redox Reactions.

Designing electrocatalysts with high activity and durability for multistep reduction and oxidation reactions is challenging. High-entropy alloys (HEAs) are intriguing due to their tunable geometric and electronic structure through entropy effects. However, understanding the origin of their exceptional performance and identifying active centers is hindered by the diverse microenvironment in HEAs. Herein, NiFeCoCuRu HEAs designed with an average diameter of 2.17 nm, featuring different adsorption capacities for various reactants and intermediates in Li-mediated CO2 redox reactions, are introduced. The electronegativity-dependent nature of NiFeCoCuRu HEAs induces significant charge redistribution, shifting the d-band center closer to Fermi level and forming highly active clusters of Ru, Co, and Ni for Li-based compounds adsorptions. This lowers energy barriers and simultaneously stabilizes *LiCO2 and LiCO3+CO intermediates, enhancing the efficiency of both CO2 reduction and Li2CO3 decomposition over extended periods. This work provides insights into specific active site interactions with intermediates, highlighting the potential of HEAs as promising catalysts for intricate CO2 redox reactions.

Tailoring competitive adsorption sites of hydroxide ion to enhance urea oxidation-assisted hydrogen production

Alloys with bimetallic electron modulation effect are promising catalysts for the electrooxidation of urea. However, the side reaction oxygen evolution reaction (OER) originating from the competitive adsorption of OH− and urea severely limited the urea oxidation reaction (UOR) activity on the alloy catalysts. This work successfully constructs the defect-rich NiCo alloy with lattice strain (PMo-NiCo/NF) by rapid pyrolysis and co-doping. By taking advantage of the compressive strain, the d-band center of NiCo is shifted downward, inhibiting OH− from adsorbing on the NiCo site and avoiding the detrimental OER. Meanwhile, the oxygenophilic P/Mo tailored specific adsorption sites to adsorb OH− preferentially, which further released the NiCo sites to ensure the enriched adsorption of urea, thus improving the UOR efficiency. As a result, PMo-NiCo/NF only requires 1.27 V and −57 mV to drive a current density of ±10 mA cm−2 for UOR and hydrogen evolution reaction (HER), respectively. With the guidance of this work, reactant competing adsorption sites could be tailored for effective electrocatalytic performance.

One‐Pot Synthesis of Carbon‐Supported Pd Nanoparticles with Ni and Carbon Matrix Protection for Durable Alkaline Hydrogen Oxidation Reaction

Protecting nanoparticles with a carbon matrix can enhance the durability of the catalysts in alkaline fuel cells (AFC) and is well‐documented. While others have tried complex syntheses to produce small nanoparticle catalysts, in this work, in order to scale‐up batches of 15 g or more, carbon‐cap (or carbon‐coating) protected Vulcan XC72‐supported Pd‐Ni (1‐2) nanoparticles (Pd‐Niacc/C) were successfully synthesized via a one‐step dry‐synthesis process. This catalyst was compared with a commercial Pd‐Ni/Vulcan XC72 material (PdNi/C, Premetek) in terms of hydrogen oxidation reaction (HOR) activity and stability. To produce less ordered carbon caps (versus graphite/graphene), a low‐temperature heat‐treatment (below 500°C) was used, resulting in Pd‐Niacc/C of unique electrochemical properties: easily electrochemically activated, this catalyst outperforms PdNi/C for alkaline HOR and proves more durable under highly oxidizing accelerated stress test (AST) conditions. Identical location transmission electron microscopy (ILTEM), X‐ray photoelectron spectroscopy (XPS) and rotating disk electrode (RDE) measurements demonstrate how the Ni‐rich surface plays an important role in HOR activity for both PdNi/C and PdNiacc/C and that the protective carbon‐coating of the latter ensures better durability of performance and better resistance to materials degradation.

Temperature-Induced Interface Hybridization of WC Boosts NiCu Activity for Alkaline Hydrogen Oxidation Reaction.

The development of non-precious hydrogen oxidation reaction (HOR) catalysts is a major challenge for the commercialization of Pt-free fuel cells. Herein, a temperature-induced phase hybridization method is reported that greatly improves the catalytic performance of NiCu alloy for the HOR. The migration of W atoms hybridizes the interface of tungsten oxide (WOx) and tungsten carbide (WC) at the onset reduction temperature of WOx, leading to a greatly weakened H binding energy and an optimized OH binding energy, which endows NiCuW/WOx-WC@WC with favorable stability and CO resistance during HOR. The hybridization catalysts deliver a high mass activity of 29.37 mA mg-1 Ni and reach a peak power of 298 mW.cm-2 in H2-O2 anion exchange membrane fuel cells (AEMFCs).

Synthesis of Solvent-Mediated Morphology-Controlled PdSn Alloy Nanocatalysts and their Application in Electrocatalysis of Ethylene Glycol and Ethanol.

2D nanodendrites (NDs) and nanosheets (NSs) have been regarded as efficient nanocatalysts for enhancing the electrocatalytic performance due to their low coordinated sites and abundant electrocatalytic centers. Nevertheless, it remains challenging to construct advanced NDs and NSs in a single reaction system. Herein, by tuning the volume ratios of mixed solvents, the reduction and diffusion rate of Sn2+ on Pd NSs template was rationally controlled to prepare PdSn NDs and PdSn NSs. Ascribed to the open 2D nanostructure, high specific surface area, and robust synergistic effect, the as-prepared PdSn NDs and PdSn NSs exhibited distinguished electrocatalytic activities for ethylene glycol oxidation reaction (EGOR) and ethanol oxidation reaction (EOR), as well as commendable electrocatalytic durability, which were far superior to the Pd NSs and commercial Pd/C. In addition, the PdSn NDs exhibited enhanced reaction kinetics because the characteristic branch structure exposed a high density of active sites. This work may provide significant guidance for preparing excellent nanocatalysts with various morphological features by simply optimizing the content of the coexisting solvents.

Ni─Co─O─S Derived Catalysts on Hierarchical N-doped Carbon Supports with Strong Interfacial Interactions for Improved Hybrid Water Splitting Performance.

Simultaneously improving electrochemical activity and stability is a long-term goal for water splitting. Herein, hierarchical N-doped carbon nanotubes on carbon nanowires derived from PPy are grown on carbon cloth, serving as a support for NiCo oxides/sulfides. The hierarchical electrodes annealed in N2 or H2/N2 display improved intrinsic activity and stability for hydrogen evolution reaction (HER) and glucose oxidation reaction. Compared with Pt/C||Ir/C in alkaline media, the glucose electrolysis assembled with electrodes exhibits a cell voltage of 1.38V at 10mAcm-2, durability for >12h at 50mAcm-2, and resistance to glucose/gluconic acid poisoning. In addition, electrocatalysts can also be applied in ethanol oxidation reactions. Systematic characterizations reveal the strong interactions between NiCo and N-doped carbon support-induced partial charge transfer at the interface and regulate the local electronic structure of active sites. Density functional theory calculations demonstrate that the synergistic effect between N-doped carbon supports, metallic NiCo, and NiCo oxides/sulfides optimize the adsorption energy of H2O and the H* free energy for HER. The energy barrier of the dehydrogenation of glucose effectively decreased. This work will attract attention to the role of metal-support interactions in enhancing the intrinsic activity and stability of electrocatalysts.

Medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 as a promising bifunctional electrocatalyst for electrochemical energy conversion device

Reversible solid oxide cells (R-SOCs) are considered to be a promising energy conversion device that can achieve efficient conversion between fuel and electrical energy. However, there are still significant challenges in developing a promising bifunctional electrocatalyst as an electrode material for R-SOC devices. Here, a medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 (PBCLCF) is designed to enhance the electrochemical oxidation and reduction activity. Under hydrogen atmosphere, cobalt metals are in situ exsolved from the perovskite structure, accompanied by partial phase transformation (denoted as R-PBCLCF). Characterizations show that PBCLCF and R-PBCLCF can increase the concentration of oxygen vacancies, thereby enhancing oxygen migration ability. Combined with electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis, the medium-entropy PBCLCF exhibits better oxygen reduction reaction (ORR) activity and R-PBCLCF shows better hydrogen oxidation reaction (HOR) activity. Furthermore, the oxygen dissociation is identified as the rate-determining step (RDS) in the ORR process, whereas the HOR process is dominated by the hydrogen adsorption and dissociation. The single cell with (R-)PBCLCF showcases remarkable reversible performance. When O2 is employed as the oxidant and H2 as the fuel, this cell achieves a maximum power density of 468.1 mW cm−2 in solid oxide fuel cell (SOFC) mode at 700 °C. Moreover, when O2 is employed as the oxidant and humidified H2 (30 %H2O) as the fuel, the current density of the cell in solid oxide electrolysis cell (SOEC) mode is −647.3 mA cm−2 at 1.3 V and 700 °C.

Controlled synthesis of Co3O4@CoP heterostructured nanoarrays as efficient electrocatalysts in alkaline seawater and urea

How to prepare clean energy has always been a problem to be solved by the modern green chemical industry. Compared with the electrolysis of water to produce hydrogen, electrolysis of seawater for raw material requirements are lower and more widely used. However, the lacks of maturity of the technology, the high cost and the generation of harmful gases such as chlorine in the electrocatalytic process have hindered the development of this process. This study demonstrates a construction of heterogeneous structure based on Co ions as an efficient multifunctional catalyst for overall seawater splitting and urea oxidation. This hybrid structure can combine nanosheets and nanowires, thus exposing the catalyst to more active sites and shortening the ion diffusion path. Comparing the hybrid structure with the single structure, Co3O4@CoP exhibits excellent multifunctional catalytic activity in alkaline seawater and urea. In the oxygen evolution reaction, the working potential is only 1.60 V and 1.70 V at a current density of 50 mA/cm2 and 100 mA/cm2. And in the hydrogen evolution reaction, the working potential was only −0.16 V at a current density of −10 mA/cm2, demonstrating excellent bifunctional activity. On this basis, the catalyst also demonstrated excellent activity for urea oxidation reaction in alkaline environment, with an operating potential of only 1.28 V at a current density of 10 mA/cm2. And the durability of this catalyst is good, it can keep 5 mA/cm2 for 12 h under the constant voltage of 1.45 V, but the initial potential falls off too fast, and there is a decline in performance, which is closely related to the corrosion of Cl- present in seawater. It was shown by density functional theory (DFT) that hierarchical nanostructures can increase the transfer rate of reaction intermediates and the water adsorption energy. At the end of this study, by comparing single nanostructures with hybrid nanostructures, it can be reasonably conjectured that the accompanying increase in the number the heterostructure is resistant to Cl- corrosion in seawater.

Metallic Cu-incorporated NiFe layered double hydroxide nanosheets enabling energy-saving hydrogen generation from chlorine-free seawater electrolysis coupled with sulfion upcycling

Development of multifunctional non-noble electrocatalysts for seawater electrolysis is imperative but still challenging for scale-up hydrogen production to avoid harmful chlorine chemistry. Herein, the metallic Cu-incorporated NiFe layered double hydroxide (LDH) nanosheets are prepared by a facile consecutive corrosion strategy using iron foam (IF) as a reactive substrate, which enable the corrosion-resistant and chlorine-free seawater electrolysis combined with anodic sulfion oxidation for energy-efficient hydrogen production at ultralow electricity consumption. The NiFe-LDH/Cu-IF exhibits excellent electrocatalytic activities for hydrogen evolution reaction (HER) and sulfion oxidation reaction (SOR), achieving low potentials of 0.203 and 0.310 V (vs RHE) at 100 mA cm−2 in alkaline seawater, respectively. The assembled hybrid HER||SOR seawater electrolyzer realizes the ultra-low cell voltage of 0.619 V and power consumption of 1.48 kWh/m3 H2 at 50 mA cm−2, cutting energy consumption over 67 % compared to conventional seawater electrolysis.

Cobalt and nitrogen co-modified hollow periodic mesoporous organosilica spheres for selective oxidation of aryl alkanes

Hollow periodic mesoporous organosilica spheres (HPMOs) have stimulated great research interest owing to its unique organic–inorganic hybrid skeleton. In this work, HPMOs were synthesized by hydrothermal method, and then cobalt and nitrogen co-doped carbon catalyst was prepared by using HPMOs as supports. The optimal catalyst (Co-Nx/HPMOs-D) performed excellent activity in the selective oxidation reaction of aryl alkanes, with the conversion of ethylbenzene up to 97.0% and the selectivity of acetophenone was 98.9%, which was attributed to the Co-Nx active species and the unique HPMOs supports. The unique amphiphilic property of Co-Nx/HPMOs-D could better facilitate the adsorption and diffusion of organic substrates in the aqueous phase. The addition of dicyandiamide not only enhanced the nitrogen content in the catalyst, but also promoted the conversion of pyrrolic-N to pyridinic-N during the pyrolysis process, thus strengthened the interaction between the substrate and cobalt and improved the stability of the catalyst. This work presented a green and environmentally friendly method for the preparation of HPMOs and a facile strategy to obtain high performance catalysts for selective oxidation of aryl alkanes.

Synergistic interactions of electronic modulation and low crystallization in Ru-RuO2/C heterostructure for highly efficient multifunctional electrocatalysis

Developing electrocatalysts with multifunctional performance is crucial for hydrogen energy storage and conversion, but still a great challenge. Herein, an efficient trifunctional electrocatalyst with heterostructure is fabricated by a sequential reduction and annealing approach. With different annealing atmospheres, Ru-RuO2/C electrocatalysts having different Ru/RuO2 atomic ratios or different crystallinities were achieved. Among these electrocatalysts, Ru-RuO2/C annealed from N2-air mixed atmosphere (Ru-RuO2/C 250NA) displays the most excellent performance, affording overpotential values of 30.63 mV for alkaline hydrogen evolution reaction (HER) and 273.42 mV for alkaline oxygen evolution reaction (OER) at 10 mA cm−2, much lower than those of state-of-the-art Pt/C (η10, HER = 46.57 mV) and RuO2 (η10, OER = 288.99 mV). Not only that, it also delivers favorable activity for alkaline hydrogen oxidation reaction (HOR), with 2.1 times of mass specific exchange current density than that of Pt/C. The experimental and theoretical investigations prove the electron rearrangement at Ru and RuO2 interface with abundant defects and amorphous/crystalline structures. The synergistic effect of dual active sites simultaneously optimizes H and OH as well as H2O adsorption energies, endowing the Ru-RuO2/C 250NA as the preferential electrocatalysts.

Regulation of hydrogen binding energy via oxygen vacancy enables an efficient trifunctional Rh-Rh2O3 electrocatalyst for fuel cells and water splitting

Developing multi-functional electrocatalysts is of great practical significance for fuel cells and water splitting. Herein, Rh-Rh2O3 nanoclusters are prepared and the surface oxygen vacancy content is regulated elaborately by post-treatment. The optimized Rh-Rh2O3/C-400 exhibits superior trifunctional catalytic activity for hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR), i.e., the mass activity for HOR is 2.29 mA μgRh-1, and the overpotential for HER and HzOR at 10 mA cm−2 is as low as 12 mV and 31 mV, respectively, superior to the benchmark Pt/C. Rh-Rh2O3/C-400 also displays promising performance in practical devices, with the H2-O2 anion-exchange-membrane fuel cell delivering a peak power density of 0.66 W cm−2, and the hydrazine-assisted water splitting electrolyzer requiring a low electrolysis voltage of 0.161 V at 0.1 A cm−2. The experimental and theoretical investigations discover that the hydrogen binding energy (HBE) is linearly depended on surface oxygen vacancy contents, and the HBE directly determines the catalytic activity for HOR, HER and HzOR. This work not only innovates an efficient Rh-based nanocluster tri-functional electrocatalyst, but also eludicates the intrinsic relationship of surface structure-intermediate adsorption-catalytic activity.

Pd-Based Bimetallic Electrocatalysts for Hydrogen Oxidation Reaction in 0.1 M KOH Solution.

A series of carbon black-supported 7.5 wt.% Pd-2.5 wt.% M/C (M: Ag, Ca, Co, Cu, Fe, Ni, Ru, Sn, Zn) electrocatalysts, synthesized via the wet impregnation method, and reduced at 300 °C, were compared in terms of their hydrogen oxidation reaction (HOR) activity in a 0.1 M KOH solution using the thin-film rotating-disk electrode technique. Moreover, 10 wt.% Pd/C and 10 wt.% Pt/C electrocatalysts were prepared in the same manner and used as references. The 7.5 wt.% Pd-2.5 wt.% Ni/C electrocatalyst exhibited the highest HOR activity among the Pd-based electrocatalysts, although it was lower than that of the 10 wt.% Pt/C. Its activity was also found to be higher than that of Pd-Ni electrocatalysts of the same total metal loading (10 wt.%) and reduction temperature (300 °C) but of different Pd to Ni atomic ratio. It was also higher than that of 7.5 wt.% Pd-2.5 wt.% Ni/C electrocatalysts that were reduced at temperatures other than 300 °C. The superior activity of this electrocatalyst was attributed to an optimum value of the hydrogen binding energy of Pd, which was induced by the presence of Ni (electronic effect), as well as to the oxophilic character of Ni, which favors adsorption on the Ni surface of hydroxyl species that readily react with adsorbed hydrogen atoms on neighboring Pd sites in the rate-determining step.

Oxygen vacancy based WO3/SnO2-x promote electrochemical H2O2 accumulation by two-electron water oxidation reaction and toxic uniform dimethylhydrazine degradation

The key to constructing an anodic electro-Fenton system hinges on two pivotal criteria: enhancing the catalyst activity and selectivity in water oxidation reaction (WOR), while simultaneously inhibiting the decomposition of hydrogen peroxide (H2O2) which is on-site electrosynthesized at the anode. To address the issues, we synthesized novel WO3/SnO2-x electrocatalysts, enriched with oxygen vacancies, capitalize on the combined activity and selectivity advantages of both WO3 and SnO2-x for the two-electron pathway electrocatalytic production of H2O2. Moreover, the introduction of oxygen vacancies plays a critical role in impeding the decomposition of H2O2. This innovative design ensures that the Faraday efficiency and yield of H2O2 are maintained at over 80 %, with a noteworthy production rate of 0.2 mmol h−1 cm−2. We constructed a novel electro-Fenton system that operates using only H2O as its feedstock and applied it to treat highly toxic uniform dimethylhydrazine (UDMH) from rocket launch effluent. Our experiments revealed a substantial total organic carbon (TOC) removal, achieving approximately 90 % after 120 mins of treatment. Additionally, the toxicity of N-nitrosodimethylamine (NDMA), a byproduct of great concern, was shown to be effectively mitigated, as evidenced by acute toxicity evaluations using zebrafish embryos. The degradation mechanism of UDMH is predominantly characterized by the advanced oxidative action of H2O2 and hydroxyl radicals, as well as by complex electron transfer processes that warrant further investigation.

Tailoring the Electronic Metal-Support Interactions in Supported Silver Catalysts through Al modification for Efficient Ethylene Epoxidation.

Metal-modified catalysts have attracted extraordinary research attention in heterogeneous catalysis due to their enhanced geometric and electronic structures and outstanding catalytic performances. Silver (Ag) possesses necessary active sites for ethylene epoxidation, but the catalyst activity is usually sacrificed to obtain high selectivity towards ethylene oxide (EO). Herein, we report that using Al can help in tailoring the unoccupied 3d state of Ag on the MnO2 support through strong electronic metal-support interactions (EMSIs), overcoming the activity-selectivity trade-off for ethylene epoxidation and resulting in a very high ethylene conversion rate (~100 %) with 90 % selectivity for EO under mild conditions (170 °C and atmospheric pressure). Structural characterization and theoretical calculations revealed that the EMSIs obtained by the Al modification tailor the unoccupied 3d state of Ag, modulating the adsorption of ethylene (C2H4) and oxygen (O2) and facilitating EO desorption, resulting in high C2H4 conversion. Meanwhile, the increased number of positively charge Ag+ lowers the energy barrier for C2H4(ads) oxidation to produce oxametallacycle (OMC), inducing the unexpectedly high EO selectivity. Such an extraordinary electronic promotion provides new promising pathways for designing advanced metal catalysts with high activity and selectivity in selective oxidation reactions.

Tailoring the Electronic Metal‐Support Interactions in Supported Silver Catalysts through Al modification for Efficient Ethylene Epoxidation

AbstractMetal‐modified catalysts have attracted extraordinary research attention in heterogeneous catalysis due to their enhanced geometric and electronic structures and outstanding catalytic performances. Silver (Ag) possesses necessary active sites for ethylene epoxidation, but the catalyst activity is usually sacrificed to obtain high selectivity towards ethylene oxide (EO). Herein, we report that using Al can help in tailoring the unoccupied 3d state of Ag on the MnO2 support through strong electronic metal‐support interactions (EMSIs), overcoming the activity‐selectivity trade‐off for ethylene epoxidation and resulting in a very high ethylene conversion rate (~100 %) with 90 % selectivity for EO under mild conditions (170 °C and atmospheric pressure). Structural characterization and theoretical calculations revealed that the EMSIs obtained by the Al modification tailor the unoccupied 3d state of Ag, modulating the adsorption of ethylene (C2H4) and oxygen (O2) and facilitating EO desorption, resulting in high C2H4 conversion. Meanwhile, the increased number of positively charge Ag+ lowers the energy barrier for C2H4(ads) oxidation to produce oxametallacycle (OMC), inducing the unexpectedly high EO selectivity. Such an extraordinary electronic promotion provides new promising pathways for designing advanced metal catalysts with high activity and selectivity in selective oxidation reactions.