Design Of New Catalysts Research Articles

Water-promoted oxidative coupling of aromatics with subnanometer palladium clusters confined in zeolites

A fundamental understanding of the active sites in working catalysts can guide the rational design of new catalysts with improved performances. In this work, we have followed the evolution of homogeneous and heterogeneous Pd catalysts under the reaction conditions for aerobic oxidative coupling of toluene for the production of 4,4′-bitolyl. We have found that subnanometer Pd clusters made with a few Pd atoms are the working active sites in both homogeneous and heterogeneous catalytic systems. Moreover, water can promote the activity of Pd clusters by nearly one-order magnitude for oxidative coupling reaction by facilitating the activation of O2. These new insights lead to the preparation of a catalyst made with Pd clusters supported on a two-dimensional zeolite, which expands the scope of the oxidative coupling of aromatics to larger substrates.

Controlling Chemoselectivity in Ruthenium(II)-Induced Cyclization of Aniline-Functionalized Alkynes.

The cyclization of heteroatom-functionalized alkynes induced by d6-transition-metal centers has traditionally been associated with the vinylidene pathway. However, recent evidence suggests that d6-transition-metal centers can also activate alkynes through non-vinylidene pathways. In this study, we conducted a comprehensive experimental and theoretical investigation into the reactions between the Ru(II) complex [Ru([9]aneS3)(bpy)(OH2)]2+ and 2-alkynylanilines. Our study revealed that the selectivity between the vinylidene and non-vinylidene pathways can be tuned by reaction temperature, substrate, and solvent polarity. This strategic control allows for the preferential formation of either C2- or C3-metalated indole zwitterion complexes. Additionally, we identified a rare decyclization mechanism that enables the conversion of C2-metalated indoles to C3-metalated indoles, underscoring the significance of product stability in these pathways. Overall, this work demonstrates practical approaches to control the preference between vinylidene and non-vinylidene pathways, which is crucial for the design of new catalysts and metalated heterocyclic complexes.

On-Demand Catalysed n-Doping of Organic Semiconductors.

A new approach to control the n-doping reaction of organic semiconductors is reported using surface-functionalized gold nanoparticles (f-AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n-type dopant precursor N-DMBI-H with several molecular and polymeric semiconductors at different temperatures with/without f-AuNPs, vis-à-vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that while f-AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~10-140 S cm-1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions and will broaden the use of the corresponding n-doped films in opto-electronic devices such as thin-film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts.

On‐Demand Catalysed n‐Doping of Organic Semiconductors

AbstractA new approach to control the n‐doping reaction of organic semiconductors is reported using surface‐functionalized gold nanoparticles (f‐AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n‐type dopant precursor N‐DMBI‐H with several molecular and polymeric semiconductors at different temperatures with/without f‐AuNPs, vis‐à‐vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that while f‐AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~10–140 S cm−1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions and will broaden the use of the corresponding n‐doped films in opto‐electronic devices such as thin‐film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts.

Theoretical Study on the Reaction between Carcinogenic 2,5-Dichloro-1,4-benzoquinone and tert-Butyl Hydroperoxide: Self-Catalysis and Water Catalysis.

The potentially carcinogenic halobenzoquinones (HBQs) have been recently identified in drinking water as disinfection byproducts. Several radical intermediates in the reaction of 2,5-dichloro-1,4-benzoquinone (DCBQ) and t-butyl hydroperoxide (t-BuOOH), which may induce DNA damage, were detected experimentally, and metal-independent decomposition reactions of t-BuOOH by DCBQ were proposed. It has not yet been confirmed by theoretical calculations. The theoretical study in this work provides insights into the details of the reaction. An unprecedented self-catalysis mechanism of organic hydroperoxides, that is, the reactant t-BuOOH also has a catalytic effect, was uncovered at the molecular level. Moreover, as the solvent, water molecules also clearly have an efficient catalytic effect. Due to the catalysis of t-BuOOH and water, the metal-independent reaction of t-BuOOH and DCBQ can occur under moderate conditions. Our findings about the novel catalytic effect of organic hydroperoxides t-BuOOH could offer a unique perspective into the design of new catalysts and an understanding of the catalytic biological, environmental, and air pollution reactions. Furthermore, organic hydroperoxide t-BuOOH could serve as a proton shuttle, where the proton transfer process is accompanied by simultaneous charge transfer. Therefore, organic hydroperoxides may disrupt the vital proton transfer process in biological systems and may give rise to unexpected toxicity.

Cooperative Cu with defective MXene for enhanced nitrate electroreduction to ammonia

AbstractThe electroreduction of nitrate (NO3RR) to ammonia (NH3) provides a promising solution to enable environmental remediation caused by ‐containing waste and also allows for energy‐saving NH3 generation. Adsorption of *NO2 intermediate may be strengthened to decrease byproducts (e.g., ) and favor the eight‐electron NO3RR into NH3. In this work, copper‐incorporated O‐vacancy containing Ti3C2 MXene (Cu@Ti3C2Ov) is reported, which cooperatively inhibits production and facilitates hydrogenation, leading to approximately 100% Faradaic efficiencies of NH3 and high yield rates at various potentials. Density functional theory calculations show that and the *NO2 intermediates have a significant interaction with the Cu@Ti3C2Ov catalyst. Moreover, the formation of has a high energy barrier, which explains the appealing catalytic performance of the Cu@Ti3C2Ov toward NO3RR with suppressed and elevated NH3 selectivity. This work would motivate the prudent design of new catalysts for high‐performance NO3RR to NH3 by elucidating the significance of stabilizing the *NO2 intermediate.

Thio-Induced Organophosphate Breakdown Promoted by Methimazole: an Experimental and Theoretical Study.

Investigating the reactivity of small nucleophilic scaffolds is a strategic approach for the design of new catalysts aiming at effective detoxification processes of organophosphorus compounds. The drug methimazole (MMZ) is an interesting candidate featuring two non-equivalent nucleophilic centers. Herein, phosphoryl transfer reactions mediated by MMZ were assessed by means of spectrophotometric kinetic studies, mass spectrometry (MS) analyses, and density functional theory (DFT) calculations using the multi-electrophilic compound O,O-diethyl 2,4-dinitrophenyl phosphate (DEDNPP). MMZ anion acts primarily as an S-nucleophile, exhibiting a nucleophilic activity comparable to that of certain oximes featuring alpha-effect. Selective nucleophilic aromatic substitution was observed, consistent with the DFT prediction of a low energy barrier. Overall, the results bring important advances regarding the mechanistic understanding of nucleophilic dephosphorylation reactions, which comprises a strategic tool for neutralizing toxic organophosphates, hence promoting chemical security.

Understanding the role of supported Rh atoms and clusters during hydroformylation and CO hydrogenation reactions with in situ/operando XAS and DRIFT spectroscopy.

Supported Rh single-atoms and clusters on CeO2, MgO, and ZrO2 were investigated as catalysts for hydroformylation of ethylene to propionaldehyde and CO hydrogenation to methanol/ethanol with in situ/operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS). Under hydroformylation reaction conditions, operando spectroscopic investigations unravel the presence of both single atoms and clusters and detected at first propanal and then methanol. We find that the formation of methanol is associated with CO hydrogenation over Rh clusters which was further confirmed under CO hydrogenation conditions at elevated pressure. The activity of catalysts synthesized via a precipitation (PP) method over various supports towards the hydroformylation reaction follows the order: Rh/ZrO2 > Rh/CeO2 > Rh/MgO. Comparing Rh/CeO2 catalysts synthesized via different methods, catalysts prepared by flame spray pyrolysis (FSP) showed catalytic activity for the hydroformylation reaction at lower temperatures (413 K), whereas catalysts prepared by wet impregnation (WI) showed the highest stability. These results not only provide fundamental insights into the atomistic level of industrially relevant reactions but also pave the way for a rational design of new catalysts in the future.

Ring-opening metathesis polymerization with 2–5 orders of rate increment

Re-coordination-suppressed ROMP achieved by a binary mechanism pathway with 2–5 orders of rate increment.

Hydrogen oxidation reaction catalysts derived from Co, Ni-coordination compounds and polymers (MOFs)

Aiming to obtain catalysts for the Hydrogen Oxidation Reaction (HOR) and to construct fuel cells completely free of noble metals, two Ni-MOFs, a Ni-coordination polymer, and a Ni-complex were synthesized, together with their corresponding Co and NiCo analogs. The following N-heterocyclic ligands were employed: 2-Methylimidazolate, imidazolate, nicotinate, 2,3-pyrazinedicarboxylate and pyrazinecarboxylate. These precursor compounds were pyrolyzed at 700 °C obtaining metallic nanoparticles embedded within N-doped mesoporous carbons. These materials were characterized by different physical and electrochemical techniques. The catalysts exhibited HOR activities (jη = 50 mv) comparable to the best-reported materials, i.e.: 1.3 and 0.6 mA cm−2disk for the Ni imidazolate and Ni nicotinate derived materials respectively. The results are relevant for the design of new catalysts and to construct alkaline anion exchange membrane fuel cells completely free of platinum group metals.

Design of Mo2C-MoP heterostructure hydrogen and oxygen evolution bifunctional catalyst based on first principles

A crucial step in resolving the energy crisis and achieving carbon neutrality is the design of bifunctional allolytic water catalysts with good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) capabilities because fuel cells are one of the crucial elements of future power systems and require good hydrogen and oxygen ends as fuel internally. In order to investigate the catalytic performance of Mo2C-MoP heterojunction bifunctional catalysts throughout the entire hydrolysis reaction, first-principles construction methods were used. It was discovered that Mo2C-MoP heterojunction catalysts have excellent hydrogen evolution effect under acidic environment through analysis and discussion of electronic properties, adsorption energy, and active sites, especially Mo2C-MoP(P1) and Mo2C-MoP(P2) models effectively adsorb hydrogen atoms near Mo2C with the best Gibbs free energy of 0.02 eV. After that, the Mo2C-MoP(P1) This paper demonstrates that the construction of heterostructured catalysts with different stacking methods has a broad research prospect in the field of fuel cells and provides new ideas for the design of new catalysts and green energy in the future. It provides new ideas for the future design of new catalysts and green energy sources.

A Conceptual Approach for the Design of New Catalysts for Ammonia Synthesis: A Metal-Support Interactions Review.

The growing interest in green ammonia production has spurred the development of new catalysts with the potential to carry out the Haber-Bosch process under mild pressure and temperature conditions. While there is a wide experimental background on new catalysts involving transition metals, supports and additives, the fundamentals behind ammonia synthesis performance on these catalysts remained partially unsolved. Here, we review the most important works developed to date and analyze the traditional catalysts for ammonia synthesis, as well as the influence of the electron transfer properties of the so-called 3rd-generation catalysts. Finally, the importance of metal-support interactions is highlighted as an effective pathway for the design of new materials with potential to carry out ammonia synthesis at low temperatures and pressures.

Synergistic multi-adsorption of N2 on MoS2 supported single metal atoms: Enhancing electroreduction of nitrogen to ammonia

MoS2-supported transition metal single atom (TM/MoS2) is expected to exhibit good performance in N2 reduction reaction (NRR). Based on systematically investigations of the stability and potential electrocatalytic nitrogen reduction reaction (NRR) performance of 27 types of TM/MoS2, V(Nb, Ta)/MoS2 exhibit good structure stability, excellent N2 activity and high ammonia (NH3) selectivity. Three nitrogen molecules are effectively captured on V(Nb, Ta)/MoS2 and the multi-adsorption of nitrogen make Mo-top site energy favorable for all the *3N2–V(Nb, Ta)/MoS2 especially for *3N2–Nb/MoS2 the energy favorable sites shift from hollow site to Mo-top site. The NRR proceeds via distal pathway, along which the limiting potentials are calculated to be −0.55, −0.42, −0.34 V for V/MoS2, Nb/MoS2 and Ta/MoS2, respectively. The transformation of Nb/MoS2 and the multi-adsorption of *N2 make the *N2 more negatively charged and more effectively activated than single adsorbed *N2, meanwhile suppressing the production of hydrogen. This work also shows the coordination difference with and without reactants adsorption and the impact on catalytic performance, which raises the importance of considering the stability of intermediates along reaction paths during theoretical design of new catalysts.

Optimizing Cu+-Cu0 synergy by operando tracking of Cu2O nanocatalysts during the electrochemical CO2 reduction reaction

Tracking the evolution of electrocatalysts over oxide-derived Cu materials during the electrochemical CO2 reduction reaction (eCO2RR) is pivotal for optimizing the product selectivity toward desired multi-carbon (C2+) products. However, the identification of the true intermediate active catalyst is still unclear. Here, we adopted a multi-modal characterization approach, primarily based on operando powder X-ray diffraction and operando micro-Raman spectroscopy, to study three Cu2O precursors with different morphologies, namely, octahedral (O-), cubic (C-), and nanowire (N-Cu2O). This multi-modal approach allows us to investigate the Cu2O nano-crystallites from the interface to the bulk structure. The results suggested notably different electrochemical reduction kinetics. 26.1% O-Cu2O and 90.6% C-Cu2O were reduced to much smaller Cu(0) domains after two hours of time-on-stream; N-Cu2O, with notably higher surface-to-volume ratio, was completely reduced within 45 min of time-on-stream. We accordingly observed a structure-reactivity correlation where a more intricate Cu2O/Cu grain network (and hence Cu+-Cu0 junctions) as observed in O-Cu2O, can lead to stable and quantitative production of ethylene at the Faradic efficiency of around 40% (in stark contrast to those of C- and N-Cu2O). The synergy between the Cu2O and Cu phases was also verified by density functional theory calculations. The upshifted d-band center of Cu2O/Cu in O-Cu2O is the most conducive toward the production of ethylene, whereas the downshifted d-band center of Cu2O/Cu in C-Cu2O leads to a decreased production of ethylene in the expense of unwanted production of hydrogen. We envisage that system optimization and design of new catalysts will become more facile and efficient using a related multi-modal operando characterization philosophy.

Design of Cr-PNP catalysts for ethylene tri-/tetramerization assisted by a data-driven approach

The implementation of data-driven methods in the domain of transition metal catalyst design has emerged as an undeniable trend. With the Curtin-Hammett principle, the selectivity of ethylene tri-/tetramerization showed a strong correlation with the relative Gibbs free energy (ΔΔG) of the key transition states. By leveraging the machine learning method, the prediction of ethylene tri-/tetramerization can be accomplished through a database training model, thereby expediting the process of new catalysts design. Herein, we constructed a group of practical descriptors that exhibit a close relationship with the Gibbs free energy, proving to be more valuable in the design of new ligands when compared to extracting elusive descriptors from the sophisticated molecular structure. Through high-throughput screening feature selection, we established an XGBoost machine learning model for Cr bisphosphine (Cr-PNP) catalysts, enabling the power of the prediction of selectivity for ethylene tri-/tetramerization. In this work, the descriptors extracted from precatalysts only take into account the influence of the metal center and the ligands, avoiding the complicated and laborious conformational search required for predicting the selectivity of the new ligands, which effectively reduces the computational costs. Descriptor analysis, guided by the feedback from the model, allows us to identify the most influential factors governing the selectivity, which can be regulated to effectively advance the design of new catalysts. The validation performed with new ligands confirms the well-predictive performance of the model, as evidenced by the relatively low mean absolute error (MAE).

Understanding polymer-porous solid interactions based on small gas molecule adsorption behavior

Understanding the interactions between molten polymers and inorganic porous solids is critical for the heterogeneous catalytic conversion of waste polymers into useful chemicals and the fabrication of nanocomposites and nanostructured polymers. Developing experimental and theoretical approaches to quantify and understand polymer-surface interactions would be extremely useful for the design of new catalysts and composites. Here, we demonstrate that the interfacial energy between molten polystyrene (PS) or polyethylene (PE) and various inorganic surfaces prepared via atomic layer deposition (ALD) such as SiO2, TiO2, WO3, and CaCO3 are correlated with the adsorption of small molecules that bear structural similarity to the repeat unit of the two polymers. The interfacial energy inferred from the dynamics of polymer infiltration into ALD-modified porous solids is compared with the heats of adsorption of small molecules on mesoporous silica (SBA-15) modified with ALD. Both our experimental and computational results suggest a strong correlation between the polymer-solid interfacial energy and the adsorption strengths of their respective small molecules on the same surface. These results highlight that even though there are no specific modes of interaction between the polymers and the inorganic surfaces, their interaction energies vary significantly and are dominated by differences in the enthalpic interactions between each repeat unit and the solid surface. Besides providing a novel method for measuring the polymer-solid interaction, this work bridges the gap between the behavior of macromolecules on solid surfaces and the adsorption properties of small gas molecules. This understanding will have important implications for designing new catalysts for polymer upcycling and composite membranes for gas and potentially polymer separation.

Insight into the poisoning effects and mechanisms of CH3SH, CH3CH2SH, CH3SCH3, and CH3CH2SCH2CH3 on Pt/C catalysts in fuel cell HOR

Trace amounts of sulphion can threaten the performance and lifespan of proton exchange membrane fuel cells (PEMFCs). The fuel mainly originates from refinery hydrogen, in which methyl mercaptan (MeSH), ethyl mercaptan (EtSH), dimethyl sulfide (DMS) and ethyl sulfide (EMS) inevitably exist. Herein, their negative effects are investigated on PEMFC and rotating disk electrode (RDE) levels, and the poisoning mechanisms are revealed by structural characterizations and density functional theory (DFT) calculations. The result indicates that MeSH and EtSH are 1.6 times more threatening than H2S, therefore, it is essential to limit the content of MeSH and EtSH. Nevertheless, the poisoning effect of DMS and EMS is weak enough to be tolerated. Moreover, the findings that the occupation of top site on Pt (111) weakly affects the hydrogen oxidation reaction (HOR) would contribute to the design of new catalysts with stronger toxicity resistance. This work is significant for the durability improvement of PEMFCs.

NiFe Alloy Integrated with Amorphous/Crystalline NiFe Oxide as an Electrocatalyst for Alkaline Hydrogen and Oxygen Evolution Reactions.

The rational design of efficient and low-cost electrocatalysts based on earth-abundant materials is imperative for large-scale production of hydrogen by water electrolysis. Here we present a strategy to prepare highly active catalyst materials through modifying the crystallinity of the surface/interface of strongly coupled transition metal-metal oxides. We have thermally activated the catalysts to construct amorphous/crystalline Ni-Fe oxide interfaced with a conductive Ni-Fe alloy and systematically investigated their electrocatalytic performance toward the hydrogen evolution and oxygen evolution reactions (HER and OER) in alkaline solution. It was found that the Ni-Fe/oxide material with a crystalline surface oxide phase showed remarkably superior HER activity in comparison with its amorphous or poorly crystalline counterpart. In contrast, interestingly, the amorphous/poorly crystalline oxide significantly facilitated the OER activity in comparison with the more crystalline counterpart. On one hand, the higher HER activity can be ascribed to a favorable platform for water dissociation and H-H bond formation, enabled by the unique crystalline metal/oxide structure. On the other hand, the enhanced OER catalysis on the amorphous Ni-Fe oxide surfaces can be attributed to the facile activation to form the active oxyhydroxides under OER conditions. Both are explained based on density functional theory calculations. These results thus shed light onto the role of crystallinity in the HER and OER catalysis on heterostructured Ni-Fe/oxide catalysts and provide guidance for the design of new catalysts for efficient water electrolysis.

Oxygen Evolution/Reduction Reaction Catalysts: From In Situ Monitoring and Reaction Mechanisms to Rational Design

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core steps of various energy conversion and storage systems. However, their sluggish reaction kinetics, i.e., the demanding multielectron transfer processes, still render OER/ORR catalysts less efficient for practical applications. Moreover, the complexity of the catalyst-electrolyte interface makes a comprehensive understanding of the intrinsic OER/ORR mechanisms challenging. Fortunately, recent advances of in situ/operando characterization techniques have facilitated the kinetic monitoring of catalysts under reaction conditions. Here we provide selected highlights of recent in situ/operando mechanistic studies of OER/ORR catalysts with the main emphasis placed on heterogeneous systems (primarily discussing first-row transition metals which operate under basic conditions), followed by a brief outlook on molecular catalysts. Key sections in this review are focused on determination of the true active species, identification of the active sites, and monitoring of the reactive intermediates. For in-depth insights into the above factors, a short overview of the metrics for accurate characterizations of OER/ORR catalysts is provided. A combination of the obtained time-resolved reaction information and reliable activity data will then guide the rational design of new catalysts. Strategies such as optimizing the restructuring process as well as overcoming the adsorption-energy scaling relations will be discussed. Finally, pending current challenges and prospects toward the understanding and development of efficient heterogeneous catalysts and selected homogeneous catalysts are presented.

Brønsted Acids Promote Olefin Oxidations by Bioinspired Nonheme CoIII(PhIO)(OH) Complexes: A Role for Low-Barrier Hydrogen Bonds.

Introduction of Brønsted acids into biomimetic nonheme reactions promotes the oxidative ability of metal-oxygen complexes significantly. However, the molecular machinery of the promoted effects is missing. Herein, a comprehensive investigation of styrene oxidation by a cobalt(III)-iodosylbenzene complex, [(TQA)CoIII(OIPh)(OH)]2+ (1, TQA = tris(2-quinolylmethyl)amine), in the presence and absence of triflic acid (HOTf) was performed using density functional theory calculations. Results revealed for the first time that there is a low-barrier hydrogen bond (LBHB) between HOTf and the hydroxyl ligand of 1, which forms two valence-resonance structures [(TQA)CoIII(OIPh)(HO---HOTf)]2+ (1LBHB) and [(TQA)CoIII(OIPh)(H2O--OTf-)]2+ (1'LBHB). Due to the oxo-wall, these complexes (1LBHB and 1'LBHB) cannot convert to high-valent cobalt-oxyl species. Instead, styrene oxidation by these oxidants (1LBHB and 1'LBHB) shows novel spin-state selectivity, i.e., on the ground closed-shell singlet state, styrene is oxidized to an epoxide, whereas on the excited triplet and quintet states, an aldehyde product, phenylacetaldehyde, is formed. The preferred pathway is styrene oxidation by 1'LBHB, which is initiated by a rate-limiting bond-formation-coupled electron transfer process with an energy barrier of 12.2 kcal mol-1. The nascent PhIO-styrene-radical-cation intermediate undergoes an intramolecular rearrangement to produce an aldehyde. The halogen bond between the OH-/H2O ligand and the iodine of PhIO modulates the activity of the cobalt-iodosylarene complexes 1LBHB and 1'LBHB. These new mechanistic findings enrich our knowledge of nonheme chemistry and hypervalent iodine chemistry and will play a positive role in the rational design of new catalysts.