Tandem Catalysis Research Articles

Acidic Media Impedes Tandem Catalysis Reaction Pathways in Electrochemical CO2 Reduction

AbstractElectrochemical CO2 reduction (CO2R) in acidic media with Cu‐based catalysts tends to suffer from lowered selectivity towards multicarbon products. This could in principle be mitigated using tandem catalysis, whereby the *CO coverage on Cu is increased by introducing a CO generating catalyst (e.g. Ag) in close proximity. Although this has seen significant success in neutral/alkaline media, here we report that such a strategy becomes impeded in acidic electrolyte. This was investigated through the co‐reduction of 13CO2/12CO mixtures using a series of Cu and CuAg catalysts. These experiments provide strong evidence for the occurrence of tandem catalysis in neutral media and its curtailment under acidic conditions. Density functional theory simulations suggest that the presence of H3O+ weakens the *CO binding energy of Cu, preventing effective utilization of tandem‐supplied CO. Our findings also provide other unanticipated insights into the tandem catalysis reaction pathway and important design considerations for effective CO2R in acidic media.

Efficient Conversion of Syngas into Ethanol by Tandem Catalysis

Efficient Conversion of Syngas into Ethanol by Tandem Catalysis

Theoretical Study on Urea Synthesis from N2 and CO2 Catalyzed by Electrochemical Tandem Catalysis of CCFs Materials

Theoretical Study on Urea Synthesis from N2 and CO2 Catalyzed by Electrochemical Tandem Catalysis of CCFs Materials

Multistep Cascade Catalytic Reactions Employing Bifunctional Framework Compounds.

Multistep cascade reactions are important to achieve atom as well as step economy over conventional synthesis. This approach, however, is limited due to the incompatibility of the available reactive centers in a catalyst. In the present study, new MOF compounds, [Zn2(SDBA)(3-ATZ)2]·solvent, I and II, with tetrahedral Zn centers as good Lewis acidic sites and the free amino group of the 3-amino triazole ligand as a strong Lewis base center were shown to perform 4-step cascade/tandem reaction in a facile manner. Effective conversion of benzaldehyde dimethyl acetal in the presence of excess nitromethane at 100 °C in water to 1-(1,3-dinitropropan-2-yl) benzene was achieved in 10 h with yields of ∼95% (I) and ∼94% (II). This 4-step cascade reaction proceeds via deacetalization (Lewis acid), Henry (Lewis base), and Michael (Lewis base) reactions. The present work highlights the importance of spatially separated functional groups in multistep tandem catalysis─the examples of which are not common.

Tandem catalysis for enhanced CO oxidation over the Bi–Au–SiO2 interface

Tandem catalysis for enhanced CO oxidation over the Bi–Au–SiO2 interface

Enhanced Nitrate-to-Ammonia Efficiency over Linear Assemblies of Copper-Cobalt Nanophases Stabilized by Redox Polymers.

Renewable electricity-powered NO3 - reduction reaction (NO3 RR) offers a net-zero carbon route to the realization of high NH3 productivity. However, this route suffers from low energy efficiency (EE, with a half-cell EE commonly <36%), since high overpotentials are required to overcome the weak NO3 - binding affinity and sluggish NO3 RR kinetics. To alleviate this, we suggest a rational catalyst design strategy that involves the linear assembly of sub-5nm Cu/Co nanophases into sub-20nm thick nanoribbons. Our theoretical and experimental studies show that the Cu-Co nanoribbons, similar to enzymes, enable strong NO3 - adsorption and rapid tandem catalysis of NO3 - to NH3 , owing to their richly exposed binary phase boundaries and adjacent Cu-Co sites at sub-5nm distance. In-situ Raman spectroscopy further reveals that at low applied overpotentials, the Cu/Co nanophases are rapidly activated and subsequently stabilized by a specifically designed redox polymer that in situ scavenges intermediately formed highly oxidative NO2 . As a result, we achieve a stable NO3 RR with a current density of ∼450mA cm-2 , a Faradaic efficiency of >97% for the formation of NH3 , and an unprecedented half-cell EE of ∼42%. This article is protected by copyright. All rights reserved.

Electrochemical NO3- Reduction Catalyzed by Atomically Precise Ag30Pd4 Bimetallic Nanocluster: Synergistic Catalysis or Tandem Catalysis?

Electrochemically converting NO3- compounds into ammonia represents a sustainable route to remove industrial pollutants in wastewater and produce valuable chemicals. Bimetallic nanomaterials usually exhibit better catalytic performance than the monometallic counterparts, yet unveiling the reaction mechanism is extremely challenging. Herein, we report an atomically precise [Ag30Pd4 (C6H9)26](BPh4)2 (Ag30Pd4) nanocluster as a model catalyst toward the electrochemical NO3- reduction reaction (eNO3-RR) to elucidate the different role of the Ag and Pd site and unveil the comprehensive catalytic mechanism. Ag30Pd4 is the homoleptic alkynyl-protected superatom with 2 free electrons, and it has a Ag30Pd4 metal core where 4 Pd atoms are located at the subcenter of the metal core. Furthermore, Ag30Pd4 exhibits excellent performance toward eNO3-RR and robust stability for prolonged operation, and it can achieve the highest Faradaic efficiency of NH3 over 90%. In situ Fourier-transform infrared study revealed that a Ag site plays a more critical role in converting NO3- into NO2-, while the Pd site makes a major contribution to catalyze NO2- into NH3. The bimetallic nanocluster adopts a tandem catalytic mechanism rather than a synergistic catalytic effect in eNO3-RR. Such finding was further confirmed by density functional theory calculations, as they disclosed that Ag is the most preferable binding site for NO3-, which then binds a water molecule to release NO2-. Subsequently, NO2- can transfer to the vicinal exposed Pd site to promote NH3 formation.

Thermodynamic and Mechanistic Analyses of Direct CO2 Methylation with Toluene to para-Xylene.

Direct CO2 methylation with toluene, as one of the CO2 hydrogenation technologies, exhibits great potential for the CO2 utilization to produce the valuable para-xylene (PX), but the tandem catalysis remains a challenge for low conversion and selectivity due to the competitive side reactions. The thermodynamic analyses and the comparation with two series of catalytic results of direct CO2 methylation are conducted to investigate the product distribution and possible mechanism in adjusting the feasibility of higher conversion and selectivity. Based on the Gibbs energy minimization method, the optimal thermodynamic conditions for direct CO2 methylation are 360-420 °C, 3 MPa with middle CO2/C7H8 ratio (1:1 to 1:4) and high H2 feed (CO2/H2 = 1:3 to 1:6). As a tandem process, the toluene feed would break the thermodynamic limit and has the higher potential of >60% CO2 conversion than that of CO2 hydrogenation without toluene. The direct CO2 methylation route also has advantages over the methanol route with a good prospect for >90% PX selectivity in its isomers due to the dynamic effect of selective catalysis. These thermodynamic and mechanistic analyses would promote the optimal design of bifunctional catalysts for CO2 conversion and product selectivity from the view of reaction pathways of the complex system.

Core-Shell Tandem Catalysis Coupled with Interface Engineering For High-Performance Room-Temperature Na-S Batteries.

The sluggish redox kinetics and shuttle effect seriously impede the large application of room-temperature sodium-sulfur (RT Na-S) batteries. Designing effective catalysts into cathode material is a promising approach to overcome the above issues. However, considering the multistep and multiphase transformations of sulfur redox process, it is impractical to achieve the effective catalysis of the entire S8 →Na2 Sx →Na2 S conversion through applying a single catalyst. Herein, this work fabricates a nitrogen-doped core-shell carbon nanosphere integrated with two different catalysts (ZnS-NC@Ni-N4 ), where isolated Ni-N4 sites and ZnS nanocrystals are distributed in the shell and core, respectively. ZnS nanocrystals ensure the rapid reduction of S8 into Na2 Sx (4<x≤8), while Ni-N4 sites realize the efficient conversion of Na2 Sx into Na2 S, bridged by the diffusion of Na2 Sx from the core to shell. Besides, Ni-N4 sites on the shell can also induce an inorganic-rich cathode-electrolyte interface (CEI) on ZnS-NC@Ni-N4 to further inhibit the shuttle effect. As a result, ZnS-NC@Ni-N4 /S cathode exhibits an excellent rate-performance (650 mAh g-1 at 5 A g-1 ) and ultralong cycling stability for 2000 cycles with a low capacity-decay rate of 0.011% per cycle. This work will guide the rational design of multicatalysts for high-performance RT Na-S batteries.

A review on development of a greener approach via One-Pot tandem catalysis for biofuels production

The escalating human population all over the globe has posed serious threats such asa limited supply of resources (non-renewable), increasing environmental pollution, global warming, food, and energy insecurities, and diminishing petroleum resources. To overcome these problems, much progress has been made in successful one-pot synthesis reactions in combination with the exploitation of advantages of chemoselectivity, regioselectivity, and stereoselectivity of biocatalysts or enzyme promiscuity. In the recent decades, various novel startegies and approaches have been developed intending to address above-mentione global issues. Among various sustainable platforms, one-pot tandem catalytic reactions are reported to be used extensively for synthesizing biofuels such as first generation-, second generation from end-use products which are derived from renewable biomass feedstocks. Further, this one-pot tandem catalytic conversion reaction has surfaced as a sustainable strategy to produce value-added environmentally safe products. Hence, a potential green approach toward the chemical industries. In this contribution, this review discusses the emergence of nanocatalysts for producing renewable energies, an explanation of tandem catalysis and one-pot synthesis, and further the production of biofuels via one-pot tandem catalysis with supportive examples and most important economic aspects and challenges associated with a promising novel approach.

Enhancing Electrochemical Nitrate Reduction to Ammonia over Cu Nanosheets via Facet Tandem Catalysis

AbstractElectrochemical conversion of nitrate (NO3−) into ammonia (NH3) represents a potential way for achieving carbon‐free NH3 production while balancing the nitrogen cycle. Herein we report a high‐performance Cu nanosheets catalyst which delivers a NH3 partial current density of 665 mA cm−2 and NH3 yield rate of 1.41 mmol h−1 cm−2 in a flow cell at −0.59 V vs. reversible hydrogen electrode. The catalyst showed a high stability for 700 h with NH3 Faradaic efficiency of ≈88 % at 365 mA cm−2. In situ spectroscopy results verify that Cu nanosheets are in situ derived from the as‐prepared CuO nanosheets under electrochemical NO3− reduction reaction conditions. Electrochemical measurements and density functional theory calculations indicate that the high performance is attributed to the tandem interaction of Cu(100) and Cu(111) facets. The NO2− generated on the Cu(100) facets is subsequently hydrogenated on the Cu(111) facets, thus the tandem catalysis promotes the crucial hydrogenation of *NO to *NOH for NH3 production.

Enhancing Electrochemical Nitrate Reduction to Ammonia over Cu Nanosheets via Facet Tandem Catalysis.

Electrochemical conversion of nitrate (NO3 - ) into ammonia (NH3 ) represents a potential way for achieving carbon-free NH3 production while balancing the nitrogen cycle. Herein we report a high-performance Cu nanosheets catalyst which delivers a NH3 partial current density of 665 mA cm-2 and NH3 yield rate of 1.41 mmol h-1 cm-2 in a flow cell at -0.59 V vs. reversible hydrogen electrode. The catalyst showed a high stability for 700 h with NH3 Faradaic efficiency of ≈88 % at 365 mA cm-2 . In situ spectroscopy results verify that Cu nanosheets are in situ derived from the as-prepared CuO nanosheets under electrochemical NO3 - reduction reaction conditions. Electrochemical measurements and density functional theory calculations indicate that the high performance is attributed to the tandem interaction of Cu(100) and Cu(111) facets. The NO2 - generated on the Cu(100) facets is subsequently hydrogenated on the Cu(111) facets, thus the tandem catalysis promotes the crucial hydrogenation of *NO to *NOH for NH3 production.

Thermocatalytic Dehydrogenation‐Enabled Arene‐Alkane Couplings†

Comprehensive SummaryThe direct use of non‐prefunctionalized arene and alkane as the starting materials to construct Caryl−Calkyl bond is an unfulfilled target and approaches to this challenge rarely surface in methodology studies. Current methods for thermocatalytic arene‐alkane couplings (AAC) occur with specific substrates and/or inconvenient reagents. Herein, we report a one‐pot relay bicatalysis system for AAC involving (pincer)Ir‐catalyzed alkane transfer dehydrogenation and Fe(OTf)3‐catalyzed olefin hydroarylation. This system exhibits broad scope and is particularly effective for alkylation of arenes with arylalkanes to form 1,1‐diarylalkanes with high chemo‐ and regioselectivity, making it potentially useful for late‐stage alkylation of complex molecules. Experimental mechanistic data provide a view into the factors controlling the regioselectivity. Finally, the strategy of dehydrogenation‐enabled arene‐alkane couplings has been successfully extended to a tandem catalysis by using a heterogeneous olefin hydroarylation catalyst.

CO2 hydrogenation for the production of higher alcohols: Trends in catalyst developments, challenges and opportunities

Higher alcohol (HA) synthesis via the hydrogenation of CO2 constitutes a relatively new and exciting field of research that has the potential to help towards the de-carbonization of the energy sector. The process poses formidable challenges, as it demands the formation of at least one C-C bond, when CO2 is thermodynamically stable, fully oxidized and kinetically inert. This work provides a comprehensive and critical literature review of the catalytic formulations that have been employed, in both fixed-bed and batch reactors, which include noble metal catalysts, transition metal-based systems, post-transition metal catalysts, bimetallic, multimetallic/multifunctional catalysts, Metal Organic Frameworks (MOFs), perovskite-, and zeolite-based catalysts. The critical role of promoters and supports and the effect that the reaction conditions have on performance are also discussed. Emphasis has been given to single atom catalysts (SACs), as the high specific activity of these systems seems to hold great promise for the reaction at hand. Breakthroughs made by employing the concept of tandem catalysis are also critically analyzed. This review paper also discusses the thermodynamic aspects of the reaction and the insights that have been gained regarding the reaction mechanism. Finally, it provides an overview of the direction that research may move to into the future.

Synergetic enhancement of selectivity for electroreduction of CO2 to C2H4 by crystal facet engineering and tandem catalysis over silver-incorporated-cuprous oxides

Synergetic enhancement of selectivity for electroreduction of CO2 to C2H4 by crystal facet engineering and tandem catalysis over silver-incorporated-cuprous oxides

Nanoreactor Engineering Can Unlock New Possibilities for CO2 Tandem Catalytic Conversion to C-C Coupled Products.

Climate change is becoming increasingly more pronounced every day while the amount of greenhouse gases in the atmosphere continues to rise. CO2 reduction to valuable chemicals is an approach that has gathered substantial attention as a means to recycle these gases. Herein, some of the tandem catalysis approaches that can be used to achieve the transformation of CO2 to C-C coupled products are explored, focusing especially on tandem catalytic schemes where there is a big opportunity to improve performance by designing effective catalytic nanoreactors. Recent reviews have highlighted the technical challenges and opportunities for advancing tandem catalysis, especially highlighting the need for elucidating structure-activity relationships and mechanisms of reaction through theoretical and in situ/operando characterization techniques. In this review, the focus is on nanoreactor synthesis strategies as a critical research direction, and discusses these in the context of two main tandem pathways (CO-mediated pathway and Methanol-mediated pathway) to C-C coupled products.

Preparation of monocyclic aromatic hydrocarbons from chlorine-containing mixed waste plastics via tandem catalysis coupled with hydrothermal pretreatment

Pyrolytic conversion of chlorine-containing mixed plastic (CMP) wastes into monocyclic aromatic hydrocarbons (MAHs) suffered the chlorinated pollutants and low product yield, making it difficult for continuous industrial operation. Herein, a novel method of tandem catalytic pyrolysis of CMP coupled with hydrothermal pretreatment (HY) for the clean production of high-yield MAHs was investigated. The pyrolytic kinetics of the feedstocks obtained after HY was analyzed, and the synergistic mechanism of HY and tandem catalysis over carbon-based catalyst (Fe/Ni/Mo@N/C) and zeolite (HZSM-5) was established. The results showed that the homogenization effect of HY on CMP was the key to improving its catalytic activity. High pretreatment temperature effectively weakened the branch-chain bond of the polyolefin molecules and dramatically reduced the pyrolytic activation energy of CMP. Additionally, the β-scission and alkylation reactions in the catalytic process were significantly promoted by HY, and subsequently improved the yields of toluene and xylene in HY-tandem catalysis, the selectivity of MAHs and benzene, toluene, ethylbenzene, and xylene (BTEX) reached 84.09% and 71.29%, respectively. The increased yield of BTEX favoured by the synergistic effect of pretreatment and catalysis was promoted to 351.97 mg/g in HY-tandem catalysis, whose yield was 9.52 times that of thermal pyrolysis. After the catalytic reaction of 360 min and transforming 18 times of the mixed plastic wastes, the coke amount of the microporous catalyst was still lower than 4 wt%. This work provides a potentially transformative solution to the challenge of upcycling unsorted plastic waste.

Hybrid Organometallic and Enzymatic Tandem Catalysis for Oxyfunctionalisation Reactions

AbstractUnspecific peroxygenases (UPOs) are promising biocatalysts for oxyfunctionalisation reactions, owing to their simplicity of handling, stability and robustness. A limitation of using UPOs on a large scale is their deactivation in the presence of even rather modest concentrations of H2O2, requiring a constant and controlled supply of low amount of H2O2. Herein, we report an organometallic complex [Cp*Ir(pica)NO3] {pica=picolinamidate=κ2‐pyridine‐2‐carboxamide ion (−1)} 1 capable of efficiently regenerating FMNH2 from FMN (TOF=350 h−1, 298 K), driven by NaHCOO; FMNH2, in turn, spontaneously reacts with O2 leading to H2O2. After having studied the compatibility of 1 with the UPO from Agrocybe aegerita (rAaeUPO PaDa‐I) and individuated the best experimental conditions, we applied such a hybrid catalytic tandem in some hydroxylation, epoxidation and sulfoxidation reactions. Best performances were obtained by using a 1/rAaeUPO molar ratio of 50. TONs for the biocatalyst of up to 18933 were obtained for the transformation of ethylbenzene derivatives into (R)‐1‐phenylethanols (ee&gt;99 %). 1/rAaeUPO was found to oxidise also cis‐methyl styrene (TON=13488), leading exclusively (1R,2S)‐cis‐methyl styrene oxide (ee&gt;99 %), cyclohexane (TON=1634) and thioanisole (TON=1369).

Highly Selective Biphasic System for the Cyclic Transformation of Glucose into 2,5-Bis(hydroxymethyl)furan via Tandem Catalysis

Highly Selective Biphasic System for the Cyclic Transformation of Glucose into 2,5-Bis(hydroxymethyl)furan via Tandem Catalysis

Pulsed Nitrate-to-Ammonia Electroreduction Facilitated by Tandem Catalysis of Nitrite Intermediates

Electroreduction of nitrate to ammonia offers a promising pathway for nutrient recycling and recovery from wastewater with energy and environmental sustainability. There have been considerable efforts on the regulation of reaction pathways to facilitate nitrate-to-ammonia conversion over the competing hydrogen evolution reaction but only with limited success. Here, we report a Cu single-atom gel (Cu SAG) electrocatalyst that produces NH3 from both nitrate and nitrite under neutral conditions. Given the unique mechanism of NO2- activation on Cu SAGs with spatial confinement and strengthened kinetics, a pulse electrolysis strategy is presented to cascade the accumulation and conversion of NO2- intermediates during NO3- reduction with the prohibited competition from the hydrogen evolution reaction, thus substantially enhancing the Faradaic efficiency and the yield rate for ammonia production compared with constant potential electrolysis. This work underlines the cooperative approach of the pulse electrolysis and SAGs with three-dimensional (3D) framework structures for highly efficient nitrate-to-ammonia conversion enabled by tandem catalysis of unfavorable intermediates.