Synergistic Catalysis Research Articles

Mechanistic studies on defective hBN-supported metal-nonmetal synergistic catalysis for urea electrosynthesis

This study explores electrocatalytic urea synthesis promoted by a newly-designed bimetallic-tricenter catalyst consisting of defective hexagonal boron nitride (hBN) and embedded dimerized 3d metal, by means of density functional theory calculations. Among all candidates, Mn was proved to be the most feasible catalytic center originating from its unique electronic structure and metal-support interactions. The metal-nonmetal synergistic effects of the Mn2N center effectively drive site-selective co-adsorption of CO and NO, spontaneous C-N coupling, low-energy-demand NO hydrogenation, and adequate protection of the carbonyl group, achieving highly active and selective urea production. The calculated limiting potential of urea formation is as low as −0.19 V, making it more favorable energetically compared to other competing reactions such as hydrogen evolution and NO reduction reactions.

Hierarchical Bi2Fe4O9/BiOI S-scheme heterojunctions with exceptional hydraulic shear induced photo-piezoelectric catalytic activity

Hierarchical Bi2Fe4O9/BiOI S-scheme nanoflower heterostructures are prepared by hydrothermal method, which exhibit exceptional photo-piezoelectric catalytic performance. The tight binding between the sheets ensures the efficient electron transport, and provides a large interface area and adequate reaction sites for photo-piezoelectric catalytic reactions. At the same time, because the water flow in the water body produces hydraulic shear force on the material, the material produces piezoelectric effect. Bi2Fe4O9/BiOI exhibit a remarkable degradation efficiency of 99.4% for tetracycline and a hydrogen production rate of 4089.36 µmol h−1 g−1. The observed behavior can be explained by the combined influence of the formation of S-scheme structure and the process of photo-piezoelectric catalysis, confirmed by in-situ XPS, transient/steady-state fluorescence and piezoelectric response force test. The excellent stability of the material suggests its possible use in the sectors of energy and environment. This work introduces novel concepts for the future advancement of photo-piezoelectric synergistic catalysis.

Photocatalytic Methanol Dehydrogenation Promoted Synergistically by Atomically Dispersed Pd and Clustered Pd.

Supported metal in the form of single atoms, clusters, and particles can individually or jointly affect the activity of supported heterogeneous catalysts. While the individual contribution of the supported metal to the overall activity of supported photocatalysts has been identified, the joint activity of mixed metal species is overlooked because of their different photoelectric properties. Here, atomically dispersed Pd (Pd1) and Pd clusters are loaded onto CdS, serving as oxidation and reduction sites for methanol dehydrogenation. The Pd1 substitutes Cd2+, forming hole-trapping states for methanol oxidation and assisting the dispersion of photodeposited Pd clusters. Therefore, methanol dehydrogenation on CdS with supported Pd1 and Pd clusters exhibits the highest turnover frequency of 1.14 s-1 based on the Pd content and affords H2 and HCHO with a similar apparent quantum yield of 87 ± 1% at 452 nm under optimized reaction conditions. This work highlights the synergistic catalysis of supported metal for improved photocatalytic activity.

Accelerated Solar-Driven Polyolefin Degradation via Self-Activated Hydroxy-Rich ZnIn2S4.

Degradation of polyolefin (PE) plastic by a traditional chemical method requires a high pressure and a high temperature but generates complex products. Here, sulfur vacancy-rich ZnIn2S4 and hydroxy-rich ZnIn2S4 were rationally fabricated to realize photocatalytic degradation of PE in an aqueous solution under mild conditions. The results reveal that the optimized photocatalyst could degrade PE into CO2 and CO, and PE had a weight loss of 84.5% after reaction for 60 h. Systematic experiments confirm that the synergetic effect of hydroxyl groups and S vacancies contributes to improve the photocatalytic degradation properties of plastic wastes. In-depth investigation illustrates that the active radicals attack (h+ and •OH) weak spots (C-H and C-C bonds) of the PE chain to form CO2, which is further selectively photoreduced to CO. Multimodule synergistic tandem catalysis can further improve the utilization value of plastic wastes; for example, product CO2/CO in the plastic degradation process can be converted in situ into HCOOH by coupling with electrocatalytic technology.

Nickel single-atom synergistic iron-nitrogen sites for efficient CO2 electroreduction at a wide potential range

Recently, diatomic site catalysts (DASCs) by introducing a second metal active site have become a research focus in electrochemical CO2 reduction reaction (eCO2RR), as can regulate electronic structure of metal centers and optimize reaction free energies. However, hitherto the studies on the origin of the outstanding performance of DASCs and the accurate identification of active centers are not still clear. Herein, we designed a nickel–iron diatomic site catalyst by loading highly dispersed iron phthalocyanine (FePc) on a nickel single-atom with ultrathin porous nitrogen-doped carbon nanosheet substrate (denoted as FePc/M-LNi-NC). Experimental and calculational results prove that the synergistic catalysis of FePc and carbon nanosheet based Ni single-atom endowed FePc/M-LNi-NC achieving excellent CO2 reduction performance with a maximum CO Faradaic efficiency of 98.8 % at –0.8 V vs. RHE. In particular, the current density of FePc/M-LNi-NC at −1.0 V vs. RHE in an H-type cell (−20.9 mA/cm2) is 5.6 times that of FePc (3.7 mA/cm2). Compared with M-LNi-NC, the potential range of FePc/M-LNi-NC when FECO above 95 % expands from 0.31 to 0.43 V. Density functional theory calculations reveal that the Fe site in FePc/M-LNi-NC has a lower free energy change for *COOH formation (ΔG*COOH) and CO desorption (ΔGCO) than Ni site, thus exhibits higher electrocatalytic activity. Furthermore, the ΔG*COOH on FePc/M-LNi-NC declines from 0.78 to 0.08 eV compared to M-LNi-NC, and the ΔGCO lowers from 1.36 to 0.33 eV compared to FePc, thus FePc/M-LNi-NC achieves high performance for eCO2RR at a wide potential range.

Scalable synthesis of a new {P2Mo18O62}-modified CuI/CuII-based metal–organic complex for multi-center synergistic catalysis of benzyl alcohol to benzoic acid

The scalable production of high-efficiency catalysts derived from polyoxometalates (POMs) is critically significant for advancing the catalysis sector. Herein, the synthesis of a new [P2Mo18O62]6– ({P2Mo18})-based metal–organic complex, (CuIL2)11[(CuIIL2Cl)(P2Mo18O62)2]·2L·0.5H2O (L = benzimidazole) (1), was achieved on a large scale using the one-pot method, and the complex was systematically characterized. Complex 1 is a three-dimensional (3D) supramolecular framework by hydrogen bonding interactions between [CuII0.5LCl0.5]-decorated {P2Mo18} anions and {CuIL2} metal–organic subunits. Benzyl alcohol (BA) was efficiently oxidized to benzoic acid (BZA) with complex 1 as a stable heterogeneous catalyst, exhibiting a remarkable conversion rate of nearly 100 % and an outstanding selectivity of 99.47 %. Notably, the catalytic system exhibits outstanding scalability, with no significant decrease in conversion and selectivity after a 20-fold increase in reaction scale. The remarkable efficiency is attributable to the unique multi-center synergistic catalytic mechanism of CuI, CuII, and MoVI within complex 1. These findings could provide significant insights into the rational design and synthesis of POMs-based catalytic materials with enhanced catalytic efficiency.

A novel all-solid-state Z-scheme BiVO4/Ag/Cu2O heterojunction: Photocatalytic and photothermal synergistic catalysis of tetracycline under simulated sunlight irradiation

The possible hazards posed by tetracycline (TC) to the environment and public health have made it a critical concern. In this work, the all-solid-state Z-scheme heterojunction BiVO4/Ag/Cu2O nanocomposites (NCs) were synthesized through a hydrothermal approach for the purpose of achieving efficient degradation towards TC. BiVO4/Ag/Cu2O NCs were able to efficiently degrade TC when exposed to simulated sunlight. The results showed that the photocatalytic efficiency was significantly influenced by Cu2O and Ag nanocrystals. The presence of Ag with large light absorption capability facilitated the efficient electron (e-) transfer between BiVO4 and Cu2O nanocrystals, thereby expanding the spectral range of light absorption in BiVO4/Cu2O NCs. Under photocatalytic and photothermal synergistic conditions, BiVO4/Ag/Cu2O NCs with an optimal addition of Ag were able to degrade TC within 60 min at reaction rate constant (k) of 0.04816 min−1. It was discovered that the best-performing photocatalysts (BAC-2) achieved photothermal conversion rates as high as 27.9 %, and they could exhibit outstanding photocatalytic and photothermal efficiency even after six cycles. Furthermore, the results obtained in radical trapping experiments suggested that photogenerated holes (h+), electrons (e-), superoxide radicals (·O2-), hydroxyl radicals (·OH) and singlet oxygen (1 O2) were involved in the photocatalytic degradation of TC. In the context of practical application, the effects of different initial TC concentrations and different irradiation conditions were studied in depth. In addition, the all-solid-state Z-scheme heterojunction mechanism for degrading TC was put forward. This research endeavors to broaden the application scope of all-solid-state Z-scheme heterojunction photocatalysts, with the aim of achieving significantly improved photocatalytic degradation of antibiotic pollutants.

Redox-Neutral Coupling of Allyl Alcohols with Trifluoromethyl Ketones via Synergistic Ni-Ti Bimetallic Catalysis.

A redox-neutral coupling of allyl alcohols with trifluoromethyl ketones has been developed via Ni-Ti bimetallic catalysis. This innovative method allows for the efficient synthesis of various β-tertiary trifluoromethyl alcohol-substituted ketones with yields of up to 98%. The reaction is scalable and compatible with a wide range of substrates, including complex bioactive molecules. Mechanistic studies suggest that the rate-determining step involving β-H elimination and the presence of the Ti-based Lewis acid, as well as a hydroxyl group on the substrates, is crucial for driving the reactivity of this transformation.

Boosting oxygen evolution reaction by FeNi hydroxide-organic framework electrocatalyst toward alkaline water electrolyzer

The oxygen evolution reaction plays a vital role in modern energy conversion and storage, and developing cost-efficient oxygen evolution reaction catalysts with industrially relevant activity and durability is highly desired but still challenging. Here, we report an efficient and durable FeNi hydroxide organic framework nanosheet array catalyst that competently affords long-term oxygen evolution reaction at industrial-grade current densities in alkaline electrolyte. The desirable high-intensity performance is attributed to three aspects as follows. First, two-dimensional nanosheet porous arrays with maximum specific surface facilitate mass/charge transfer to accommodate high-current-density catalysis. Second, in situ derived FeNi hydroxide motifs offer bimetallic synergistic catalysis centers with high intrinsic activity. Third, carboxyl ligands alleviate metal oxidation favorable for charge tolerability against peroxidation dissolution under strong polarization. As a result, this catalyst requires an overpotential of only 280 mV to deliver high current density up to 1 A/cm2 with long durability over 1000 h. Moreover, an alkaline water electrolyzer with this catalyst alternative demonstrates an increased economic effectiveness compared to commercial levels at present.

Synergic Catalysis: the Importance of Intermetallic Separation in Co(III)K(I) Catalysts for Ring Opening Copolymerizations.

Dinuclear polymerization catalysts can show high activity and control. Understanding how to design for synergy between the metals is important to improving catalytic performances. Three heterodinuclear Co(III)K(I) catalysts, featuring very similar coordination chemistries, are prepared with different intermetallic separations. The catalysts are compared for the ring-opening copolymerization (ROCOP) of propene oxide (PO) with CO2 or with phthalic anhydride (PA). The catalyst with a fixed, wide intermetallic separation, LwideCoK(OAc)2 (Co-K = 8.06 Å), shows very high activity for PO/PA ROCOP, but is inactive for PO/CO2 ROCOP. On the other hand, the catalyst with a fixed, narrow intermetallic separation, LshortCoK(OAc)2 (Co-K, 3.59 Å), shows high activity for PO/CO2 ROCOP, but is much less active for PO/PA ROCOP. A bicomponent catalyst system, comprising a monometallic complex LmonoCoOAc used with an equivalent of KOAc[18-crown-6], shows high activity for both PO/CO2 and PO/PA ROCOP, provided the catalyst concentration is sufficiently high, but underperforms at low catalyst loadings. It is proposed that the two lead catalysts, LwideCoK(OAc)2 and LshortCoK(OAc)2, operate by different mechanisms for PO/PA and PO/CO2 ROCOP. The new wide separation catalyst, LwideCoK(OAc)2, shows some of the best performances yet reported for PO/PA ROCOP, and suggests other catalysts featuring larger intermetallic separations should be targeted for epoxide/anhydride copolymerizations.

Effect and mechanism of graphite addition on microstructures and hydrogen storage properties of Mg–Y–Zn alloy

In this work, the Mg-9.1Y-1.0Zn alloy are prepared by semi-continuous casting, and then mechanical milled with graphite. The microstructures and hydrogen storage properties of milled composite are systematically studied. The results show that the as-cast Mg-9.1Y-1.0Zn alloy exhibits serious agglomeration after milling. The addition of graphite significantly restrains the agglomeration of alloy and further refines the particles. Compared with as-cast Mg-9.1Y-1.0Zn alloy, the hydrogen storage properties of Mg-9.1Y-1.0Zn alloy milled with graphite is greatly improved. It needs only three times activation to be fully activated and its maximum hydrogen storage capacity is about 6.7 wt%. Besides, its dehydrogenation activation energy is decreased by about 40 kJ mol−1 relative to as-cast Mg-9.1Y-1.0Zn alloy. During hydrogen absorption and desorption, the stable YH2 hydride is generated by the disproportionation decomposition of LPSO phase. The graphite and in-situ formed YH2 present the synergistic confinement and catalysis effects on the milled Mg–Y–Zn alloy particles, which is conductive to the enhancment of hydrogen storage properties.

Synergistic catalysis in Pd/La-CeO2 enhanced CH4 oxidation: The role of water and reactive oxygen species

The catalytic oxidation of methane (CH4) stands as an essential strategy for curtailing greenhouse gas emissions. This study advances CH4 oxidation using Pd on La-doped CeO2, where water (H2O) boosts oxidation efficiency. The temperature for obtaining 50 % CH4 conversion on Pd/La-CeO2 catalyst was reduced from 288 °C (without H2O) to 260 °C (with H2O), while that on CeO2 was 570 °C both under conditions with and without H2O. Operando DRIFTS analysis reveals the reaction pathway and intermediates during CH4 oxidation. Ce cations provide adsorption sites for CH4, leading to the generation of CH3 adsorbed species with the help of surface O2–. La doping creates oxygen vacancies essential for oxygen activation and foster the formation of reactive hydroxide (OH) from adsorbed H2O and O. Pd contributes to the formation of more reactive oxygen species that facilitate OH generation at La cations and the oxidation of CH4 adsorption species to CO2 and H2O. The synergistic interplay between Pd and La-CeO2 is particularly noteworthy, with H2O also playing a role in the gasification of surface carbonates, thereby enhancing the overall performance of CH4 oxidation. A kinetic model based on the Langmuir-Hinshelwood mechanism is proposed, offering an insight into CH4 oxidation.

Asymmetric Arylation of Enone Diesters Enabled by Synergistic Copper Catalysis

Asymmetric Arylation of Enone Diesters Enabled by Synergistic Copper Catalysis

Synergistic Cu Single Atoms and MoS2‐Edges for Tandem Electrocatalytic Reduction of NO3− and CO2 to Urea

AbstractUrea electrosynthesis from co‐electrolysis of NO3− and CO2 (UENC) under ambient conditions is recognized as an appealing approach for effective and sustainable urea production, while it requires high‐efficiency UENC electrocatalysts to promote the C─N coupling and hydrogenation processes. Herein, single‐atom Cu anchored on MoS2 (Cu1‐MoS2) is explored as a highly active and selective UENC catalyst. Theoretical calculations and operando spectroscopic characterizations unveil the synergistic tandem catalysis of Cu1‐MoS2 for the UENC, where Cu single atoms trigger the early C─N coupling, while MoS2‐edges promote the key hydrogenation step of *CO2NH2 to *COOHNH2 for urea generation. Strikingly, Cu1‐MoS2 equipped in a flow cell achieves the excellent UENC performance with a maximum urea‐Faradaic efficiency of 57.02% at −0.6 V and the corresponding urea yield rate of 23.3 mmol h−1 g−1, surpassing nearly all previously reported UENC catalysts.

Synthesis of Unprotected α-Tertiary Amino Acids Using Synergistic Photoenzymatic Catalysis

Synthesis of Unprotected α-Tertiary Amino Acids Using Synergistic Photoenzymatic Catalysis

Functional Ni/MnO2 heterostructure electrocatalysts based on self-sacrifice-induced LDHs anchored on nanofibers for microbial fuel cells

Designing cost-effective, highly active oxygen reduction catalysts for high-power-density microbial fuel cells (MFCs) is a significant challenge. To address this, this study uniformly dispersed layered double hydroxides (LDHs) on nanofiber surfaces, and subsequently utilized the self-sacrifice method of zeolite imidazole frameworks (ZIFs) to synthesize LDH/ZIF@CNFs bimetallic heterostructure with precise lattice matching. Experimental results collectively verified that LDH/ZIF@CNFs-12 exhibits an onset potential of -0.087 V, surpassing Pt/C (-0.098 V). Impressively, MFC equipped with LDH/ZIF@CNFs-12 achieves a high power density of 939.05 mW/cm2, surpassing Pt/C (859.74 mW/cm2). The excellent electrocatalytic performance of this catalyst originates from the rich active sites exposed in the LDHs core during the MOFs-assisted synthesis process, and the synergistic catalysis achieved by the formation of heterojunctions. In addition, 3D nanofibers uniformly disperse active sites and reduce large band gaps. This work unveils a new perspective for cost-effective, eco-friendly, and sustainable catalysts suitable for MFCs.

General Defluoroalkylation of Trifluoromethylarenes with Both Electron-Donating and -Withdrawing Alkenes.

The incorporation of gem-difluoromethylene units into organic molecules remains a formidable challenge. Conventional methodologies for constructing aryldifluoromethyl derivatives relied on the use of high-functional fluorinating regents under harsh conditions. Herein, we report general and efficient photoredox catalytic systems for defluoroalkylation of readily available trifluoromethylarenes through selective C-F cleavage to deliver gem-difluoromethyl radicals which proceed through reductive addition to both electron-donating and withdrawing alkenes under transition-metal free conditions. Mechanistic studies reveal that thiol serves as both photocatalyst and HAT reagent under visible light irradiation. This synergistic photocatalysis and HAT catalysis protocol exhibits ample and salient features such as high chemo- and regioselectivity, broad substrate scope, amenable gram-scale synthesis and late-stage modification of bioactive molecules.

Constructing homo/hetero-nuclear carbon and oxygen atoms co-doped graphitic carbon nitride assisted by ionic liquid for photothermal synergistic catalytic oxidation of cyclohexane

The adoption of photothermal synergistic catalysis for cyclohexane oxidation can balance the advantages of high conversion of thermal catalysis and high selectivity of photocatalytic technology to achieve better catalytic performance. Here, we prepared functional carbon nitride (BCA-CN) by self-assembly strategy of ionic liquid [Bmim]CA (1-Butyl-3-methylimidazole citrate) with melamine and cyanuric acid utilizing abundant elements and anionic/cationic hydrogen bonding interactions. The introduction of [Bmim]CA embeds C-C (carbon and carbon band) and C-O-C (ether bond) structures into graphitic carbon nitride (g-C3N4) framework, significantly improving light absorption capacity and migration of photo generated charge carriers. Compared to g-C3N4, both BCA-CN increases cyclohexane conversion and KA oil (the mixture of cyclohexanol and cyclohexanone) selectivity by 1.3 times under photothermal catalysis. The surface reactions are facilitated by changing adsorption sites of cyclohexane to increase adsorption energy and obtaining more hydroxyl radicals and superoxide radicals. Furthermore, the enhanced selectivity is attributed to the difficulty in generating cyclohexanone radicals. This work offers the reference scheme for the development of efficient photothermal catalysts in the selective oxidation of cyclohexane.

Cu-doped ZnCdS-based photocatalyst for efficient photocatalytic hydrogen production by photothermal assistance

In solar energy utilization, photocatalytic hydrogen production has been widely researched. To address issues such as low efficiency of photocatalysts, Cu-doped Zn0.5Cd0.5S composite photocatalysts were prepared using a hydrothermal method for photocatalytic hydrogen production. The Cu/Zn0.5Cd0.5S photocatalyst was characterized using XRD, XPS, SEM, TEM, UV–vis-DRS, fluorescence spectrophotometer, and electrochemical workstation. The results indicate that Cu doping alters the crystal and band structures of Zn0.5Cd0.5S. Hydrogen production experiments were conducted under xenon lamp irradiation, and at 45 °C, the highest hydrogen production rate was 2.72 and 1.63 times that of single Zn0.5Cd0.5S and Cu-doped Zn0.5Cd0.5S at room temperature (25 °C), respectively. Cu doping imparted a photothermal effect to the photocatalytic hydrogen production experiment, enhancing its efficiency.Cu doping captured electrons by replacing some Zn, constructing an internal electric field, forming defect energy levels, which hindered electron-hole recombination. Additionally, Cu ions acted as a plasma, inducing a plasma effect during hydrogen production, accelerating the rate of solar energy conversion to thermal energy, thus improving hydrogen production efficiency. This research not only provides a photocatalyst for photocatalytic hydrogen production but also utilizes it for photothermal synergistic catalysis.

Chemical Recycling of Poly(cyclohexene carbonate)s via Synergistic Catalysis.

Chemical recycling of polymers to the corresponding monomers offers a valuable solution to address the current plastics crisis for creating an ideal and circular polymer economy. Here, we present a bimetallic synergistic depolymerization of the widely studied CO2-based polycarbonates, poly(cyclohexene carbonate)s, to epoxide monomers efficiently. The bimetallic CrIII-complex-mediated highly selective depolymerization and repolymerization was achieved via the regulation of reaction temperature, thus closing the circular loop of poly(cyclohexene carbonate)s in situ. Mechanistic investigation has revealed that the formation of epoxides undergoes a direct chain-end unzipping process. A bimetallic catalysis involving a nucleophilic attack of the metal-alkoxide species toward the methine carbon atom bound with an adjacent carbonyl that is activated by the other metal center features a lower energy barrier in DFT calculations, which promotes the epoxide extrusion.