Bimetallic Active Sites Research Articles

A comparative study of the catalytic nitration of toluene over bimetallic Ce‐Mn modified Hβ zeolite

AbstractBimetallic cerium‐manganese modified Hβ zeolite sample (Ce/Mn‐Hβ) was prepared by ultrasonic assisted impregnation method and applied in nitration of toluene. The characterization results show that the active components (Ce and Mn) are successfully introduced into the framework of Hβ zeolite. The catalyst shows excellent catalytic activity and reusability for the nitration of toluene, giving high para selectivity. Under optimized conditions, it gives 68.7% selectivity to para‐nitrotoluene at 88.6% conversion over Ce/Mn‐Hβ in the presence of acetic anhydride (Ac2O). The theoretical calculations indicate that the Ce/Mn bimetallic active sites in modified Hβ zeolite can easily activate the nitrification reagent (AcONO2), and the enhancement of para selectivity is owing to the steric hindrance of catalyst. Furthermore, the reaction mechanism was proposed by the combination of experimental results and theoretical calculations.

Bimetallic FeCo metal-organic-frameworks anchored multi-walled carbon nanotubes for electrochemical nitrite sensing

A heterostructured nanocomposite modified electrode was designed as a sensitive and efficient analytical tool for nitrite determination. The nanocomposite constructed from different building blocks was fabricated by ultrasonically growing bimetallic FeCo metal-organic framework (MOF) in the well-dispersed multi-walled carbon nanotubes (MWCNTs) suspensions at room temperature, where the MOF hybrid was extended to uniform thin film structure. Electrochemical experimental results demonstrate that the synergistic contributions from bimetallic active sites, MWCNTs and thin-film morphology endow modified electrode with dramatically enhanced catalytic activity metrics towards nitrite. Significantly, the co-doping of Fe-Co plays key role in improving the electronic conductivity and catalytic capacity of the MOF/MWCNTs composite. Thereinto, the FeCo-MOF/MWCNTs sensor displays excellent detection performance with a wide linear detection range (5∼5000 μM), outstanding selectivity and a detect limitation of 1.68 μM for nitrite. These superior findings provide new potentials application for the inspection of nitrite in environmental monitor.

Amorphous iron-doped nickel boride with facilitated structural reconstruction and dual active sites for efficient urea electrooxidation

Designing transition metal-based catalysts for efficient urea oxidation reaction (UOR) is important for realizing energy-saving hydrogen production via urea-rich (waste)water electrolysis. Herein, we have developed an iron-doped amorphous nickel boride electrocatalyst (aFe-NiB) for UOR. Compared with the undoped and crystalline counterparts, aFe-NiB exhibits a higher activity and the benchmark current density of 10 mA cm−2 can be attained at 1.298 V vs. reversible hydrogen electrode (RHE). Coupled with an efficient hydrogen evolution catalyst, the aFe-NiB-assisted urine electrolyzer can attain a 46 times higher H2 production rate than the water electrolyzer at 1.50 V. Further study reveals a crystallinity-dependent structure self-reconstruction process during UOR. aFe-NiB attains complete phase evolution from boride to electroactive Fe-doped NiOOH. In addition, density functional theory calculations imply that Fe dopants can improve intrinsic catalytic activity via electronic structure regulation of the self-evolved NiOOH and forming heterogeneous bimetallic active sites for UOR. This study provides meaningful insights into the crystallinity-dependent UOR performance and effective strategies to develop efficient UOR (pre)catalysts with dual active sites. Significantly, the demonstrated direct wastewater (urine) electrolysis paves the way for net zero buildings -targeted human waste reutilization.

A mechanic insight into low-temperature catalytic combustion toward ethylene oxide over Pt-Ru/CuCeOx bimetallic catalyst

The catalytic oxidation performance toward ethylene oxide (EO) and the consequent mechanism were investigated on the Pt-Ru/CuCeOx bimetallic catalyst, which was prepared by a distinct method combining stepwise adsorption and subsequent impregnation. The catalytic tests show that the introduction of Ru into the Pt catalyst, so as to form Pt-Ru bimetallic active sites, can greatly increase the oxidation activity of the catalyst, as evidenced by the extremely lower full oxidation temperature (120 °C) when compared with that of the Pt/CeO2 catalyst (160 °C). The XPS spectra show that the Ru species (mainly RuOx) have strong interaction with the CuCeOx support, which can therefore affect the electron transfer between the Pt species and the support. As a result, the oxygen activation on Pt species is obviously facilitated and catalytic activity is enhanced. Finally, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) was used to track the reaction mechanism. It is found that the catalytic oxidation process follows the MvK catalytic mechanism at low temperature and the L-H catalytic mechanism when the temperature moves to higher range.

Bimetallic MOF synergy molecularly imprinted ratiometric electrochemical sensor based on MXene decorated with polythionine for ultra-sensitive sensing of catechol

Dual-signal ratiometric molecularly imprinted polymer (MIP) electrochemical sensors with bimetallic active sites and high-efficiency catalytic activity were fabricated for the sensing of catechol (CC) with high selectivity and sensitivity. The amino-functionalization bimetallic organic framework materials (Fe@Ti-MOF-NH2), coupled with two-dimensional layered titanium carbide (MXene) co-modified glassy carbon electrode provides an expanded surface while amplifying the output signal through the electropolymerization immobilization of polythionine (pTHi) and MIP. The oxidation of CC and pTHi were presented as the response signal and the internal reference signal. The oxidation peak current at +0.42 V rose with increased concentration of CC, while the peak currents of pTHi at −0.20 V remained constant. Compared to the common single-signal sensing system, this one (MIP/pTHi/MXene/Fe@Ti-MOF-NH2/GCE), a novel ratiometric MIP electrochemical sensor exhibited two segments wide dynamic range of 1.0–300 μM (R2 = 0.9924) and 300–4000 μM (R2 = 0.9912), as well as an ultralow detection limit of 0.54 μM (S/N = 3). Due to the specific recognition function of MIPs and the advantages of built-in correction of pTHi, the prepared surface imprinting sensor presented an excellent performance in selectivity and reproducibility. Besides, this sensor possessed superior anti-interference ability with ions and biomolecules, excellent reproducibility, repeatability, and acceptable stability. Furthermore, the proposed sensing system exhibits high specific recognition in the determination of environmental matrices and biological fluids in real samples with satisfactory results. Therefore, this signal-enhanced ratiometric MIP electrochemical sensing strategy can accurately and selectively analyze and detect other substances.

Niobium- and cobalt-modified dual-source-derived porous carbon with a honeycomb-like stable structure for supercapacitor and hydrogen evolution reaction

Designing porous carbon materials with tailored architecture and appropriate compositions is essential for supercapacitor (SC) and hydrogen evolution reaction (HER). Herein, Nb/Co-modified dual-source porous carbon (Nb/Co-DSPC) with a honeycomb structure was obtained by introducing a secondary carbon source (Co/Zn-ZIF) and transition metal Nb into activated Typha carbon (ATC). The addition of a secondary carbon source and Nb resulted in superior specific surface area (1272.38 m2/g), excellent hydrophilicity (34.73°) and abundant bimetallic active sites (Nb/Co-Nx) in Nb/Co-DSPC, providing excellent charge storage capacity and electrocatalytic activity. The Nb/Co-DSPC electrode displayed an outstanding capacitance of 337 F/g at 0.5 A/g and showed excellent stability after 15,000 charge–discharge cycles. In addition, Nb/Co-DSPC shows an overpotential of 114 mV at 10 mA cm−2, better than those of Co-DSPC (139 mV) and ATC (162 mV) alone. This study offers a reliable strategy for advanced multifunctional porous carbon electrode materials preparations.

Fine-tuning catalytic performance of ultrafine bimetallic nickel-platinum on metal-organic framework derived nanoporous carbon/metal oxide toward hydrous hydrazine decomposition

Heterogeneous catalysts with a high performance as well as low cost is pivotal but still challenging for hydrous hydrazine (N2H4·H2O) as a hydrogen storage material. Herein, bimetallic PtNi nanoparticles are well dispersed on nitrogen doped porous carbon/zirconia support (PtNi/NC-ZrO2). PtNi/NC-ZrO2 nanocatalysts could be responsive and completely for catalyzing hydrous hydrazine decomposition with a H2 selectivity of 100% as well as a turnover frequency of 1716 h−1 measured at 323 K, outperforming most heterogeneous metal catalysts. This is mainly attributed that bi-support NC-ZrO2 can efficiently expedite the electron transfer to metallic NPs and re-construct the electronic structure bimetallic active sites for selectively catalyzing hydrous hydrazine decomposition.

Theoretical screening of synergistic transition metal dual-atom catalysts for overall water splitting

Double-atom catalysts (DACs) with bimetallic active sites can produce a synergistic effect between the neighbouring metallic sites, which can further enhance the catalytic activity. In this work, DFT calculations are used to screen lots of DACs as effective bifunctional electrocatalysts for overall water splitting. Through the comparative study between the DACs and single-atom catalysts (SACs), we found that DACs show higher overall water splitting activity than corresponding SACs counterparts, attributing to the synergistic effect between the adjacent active sites which play a vital role in fine tuning the binding strength of the reaction intermediates. The d-band center and charge transfer as descriptors are used to explain the activity origin of DACs. This work highlights that DACs with bimetallic active sites are promising for designing bifunctional catalysts for overall water splitting.

Efficient lignin conversion over Ni/(Fe/Zn/Co/Mo/Cu)–WO3/Al2O3for selectively yielding alkyl phenols

Different combinations of bimetallic active sites produced different streams of phenolic products due to their different catalytic selectivity.

Functionalization of activated carbon fiber mat with bimetallic active sites for NH3 and H2S adsorption at room temperature

Simultaneous removal of NH3 and H2S at room temperature is of paramount significance for industrial production safety and environmental protection, which has received considerable attention recently. However, single metal compound modification is difficult to achieve highly efficient co-removal performance for NH3 and H2S. Herein, a series of adsorbents with metal chlorides and metal oxides simultaneously loaded in the activated carbon fiber mat were prepared and applied to the NH3 and H2S removal with high efficiency at room temperature. The obtained ACF-NiCl2-MgO possesses large surface area, hierarchical porous structure, as well as uniform dispersion of bimetallic active sites. The advanced porous architecture helps to ensure consistent dispersion of metallic active sites remaining residual channel for the capture of gas molecules. The metal salts facilitate the deamination ability by complexation with NH3, while metal oxides promote the desulfurization ability by chemical adsorption of H2S. The incorporation of metal chlorides and metal oxides significantly improves the adsorption performance of NH3 and H2S. Consequently, the NH3 adsorption capacity of ACF-NiCl2-MgO achieves 22.5 mg NH3/g, and the breakthrough sulfur capacity is as high as 209.2 mg H2S/g. This work provides a new method to design high-capacity binary metal compounds modified activated carbon-based adsorbents for the co-removal of NH3 and H2S at room temperature.

A Review on the Different Aspects and Challenges of the Dry Reforming of Methane (DRM) Reaction.

The dry reforming of methane (DRM) reaction is among the most popular catalytic reactions for the production of syngas (H2/CO) with a H2:CO ratio favorable for the Fischer–Tropsch reaction; this makes the DRM reaction important from an industrial perspective, as unlimited possibilities for production of valuable products are presented by the FT process. At the same time, simultaneously tackling two major contributors to the greenhouse effect (CH4 and CO2) is an additional contribution of the DRM reaction. The main players in the DRM arena—Ni-supported catalysts—suffer from both coking and sintering, while the activation of the two reactants (CO2 and CH4) through different approaches merits further exploration, opening new pathways for innovation. In this review, different families of materials are explored and discussed, ranging from metal-supported catalysts, to layered materials, to organic frameworks. DRM catalyst design criteria—such as support basicity and surface area, bimetallic active sites and promoters, and metal–support interaction—are all discussed. To evaluate the reactivity of the surface and understand the energetics of the process, density-functional theory calculations are used as a unique tool.

Electrochemical Trends of Atomically Dispersed Metal-Nitrogen-Carbon Materials As Oxygen Reduction Reaction Catalysts and Active Supports

Platinum-based catalysts currently remain the best option for polymer electrolyte membrane fuel cell (PEMFC) applications. Meanwhile, atomically dispersed metal-nitrogen-carbon (MNC) materials have been the frontrunner for platinum-group metal free catalysts for the oxygen reduction reaction (ORR)1. Considering that the platinum-based nanoparticles are preferably supported on carbonaceous materials, it would be intuitive to use MNC catalysts as a support for platinum nanoparticles to further increase the activity and performance of the catalyst layer in a PEMFC. In this work, we synthesized and investigated a series of MNC materials (Mn-N-C, Fe-N-C, Co-N-C, Ni-N-C, and Cu-N-C) using a previously described method2 to elucidate the electrochemical trends of possible interactions between the MNC materials as a support and standard Pt nanoparticles. Recent works3,4 have shown that combining MNC catalysts with Pt catalysts not only improves the activity of the overall composite catalyst, but also improves the stability of both counterparts. As shown in Figure 1, the supported Pt nanoparticles on MNC materials outperforms the same type of Pt nanoparticles when supported on an industry standard carbon.Reference Asset, T. & Atanassov, P. Iron-Nitrogen-Carbon Catalysts for Proton Exchange Membrane Fuel Cells. Joule 4, 33–44 (2020).Murphy, E. et al. Using Atomically Dispersed Bimetallic Active Sites to Probe the Nitrate Reduction Mechanism to Ammonia. ECS Meet. Abstr. MA2021-02, 1559 (2021).Ao, X. et al. Atomically dispersed Fe–N–C decorated with Pt-alloy core–shell nanoparticles for improved activity and durability towards oxygen reduction. Energy Environ. Sci. 13, 3032–3040 (2020).Qiao, Z. et al. Atomically dispersed single iron sites for promoting Pt and Pt3Co fuel cell catalysts: performance and durability improvements. Energy Environ. Sci. (2021). Figure 1

Characterizing the sequential effects toward the impregnations of supported bimetallic catalysts

Supported bimetallic catalysts have been paid great attention regarding their excellent catalytic performances in chemical process. Notably, comparing to monometallic catalysts, the synergetic properties of dual-metal-based materials demonstrate unique physiochemical functionalities that single metal materials do not possess. The preparation of supported bimetallic materials is widely conducted with applying the impregnation method because of the straightforward and inexpensive technique. Wherein, the impregnation of dual metals on support could either undergo co-impregnation or sequential impregnations. It has been frequently reported that there are substantial differences in physiochemical properties and catalyst performances by impregnation sequences. Specifically, during the investigation of various sequential impregnated bimetallic catalysts, a host of characterization strategies are employed to compare the physical and chemical properties that play vital role to impact the catalyst activity/selectivity/stability. However, it is still not well understood regarding the impregnation sequential effects, such as the nature of bimetallic active sites and the dynamics of bimetallic surface structures along with reaction progress. This presenting perspective article is devoted to take a succinct review regarding the general sequential impacts on the physiochemical properties and further profoundly address the research outlook in this topic.

Mo-decorated cobalt phosphide nanoarrays as bifunctional electrocatalysts for efficient overall water/seawater splitting

Transition metal phosphides (TMPs) are emerging as the indispensable electrocatalysts for overall water/seawater splitting, while there are ongoing challenges resulting from the poor catalytic activity and low stability, especially the electrode corrosion caused by the side reactions of chloride evolution reaction (ClER). Herein, Mo-decorated CoPX nanoarrays on nickel foam (Mo-CoPX/NF) is prepared by an in situ hydrothermal-phosphorylation method. Profiting from the unique self-supported nanoarrays, plenty of bimetallic active sites, and high conductivity, Mo-CoPX/NF nanosheet arrays show low overpotential as bifunctional electrocatalyst in water/seawater electrolytes. The Mo-CoPX/NF || Mo-CoPX/NF pair only needs 1.49 and 2.01 V to drive an overall water splitting of 10 and 100 mA cm−2, respectively, which is much better than the commercial catalysts. Moreover, with the strong inhibiting effect of ClER and corrosion resistance benefited from the synergistic effect of bimetallic atoms in phosphide, Mo-CoPX/NF || Mo-CoPX/NF pair has superb catalytic durability for seawater electrolysis.

Superior electrocatalyst based on mesoporous silica nanoparticles/carbon nanotubes modified by platinum-copper bimetallic nanoparticles for amperometric detection of hydrazine

Hydrazine is a volatile, water-soluble molecule with strong reducing ability that is widely used in various industrial and pharmaceutical fields. It is known as a combination of carcinogens and neurotoxins that have harmful effects on the liver, brain, nervous system and DNA and also cause blood disorders. Therefore, developing a sensitive, accurate, simple and fast way to measure hydrazine concentration is very important. Here, a novel and efficient sensor for the determination of hydrazine at trace level is introduced by modifying mesoporous silica nanoparticles (MSNPs)/multi-walled carbon nanotubes dispersed in carbon paste electrode with PtCu nanoparticles (PtCu NPs/MSNPs/CNTs/CPE). SBA-15 NPs as one of the MSNPs are stable matrix for bimetallic NPs which prevent their accumulation and provide conditions for low loading of catalyst due to its unique structure. For this purpose, MSNPs was firstly synthesized from stem sweep ash (SSA) as raw material. The suggested sensor indicated favorable analytical performance in 0.1 M phosphate buffer solution (PBS, pH = 7.4) with a low limit of detection (S/N = 3.3) of 0.09 μM in the wide linear range of 6 μM−17.24 mM, high sensitivity of 47.18 μA mM−1, rapid response time of ∼3 s and high repeatability/reproducibility. The analytical performance of PtCu NPs/MSNPs/CNTs/CPE originates from the presence of more available bimetallic active sites and the synergistic effect of MWCNTs with high electrical conductivity. In the presence of some usual interferences, the sensor indicated high selectivity for hydrazine detection. The practical application of PtCu NPs/MSNPs/CNTs/CPE in real samples was also evaluated. The results showed that the MSNPs with large porosity and high surface area are efficient substrate for catalyst formation and cause to fabrication of sensor with excellent accuracy, precision, and recovery for the determination of hydrazine.

Unlocking bimetallic active sites via a desalination strategy for photocatalytic reduction of atmospheric carbon dioxide

Ultrathin two-dimensional (2D) metal oxyhalides exhibit outstanding photocatalytic properties with unique electronic and interfacial structures. Compared with monometallic oxyhalides, bimetallic oxyhalides are less explored. In this work, we have developed a novel top-down wet-chemistry desalination approach to remove the alkali-halide salt layer within the complicated precursor bulk structural matrix Pb0.6Bi1.4Cs0.6O2Cl2, and successfully fabricate a new 2D ultrathin bimetallic oxyhalide Pb0.6Bi1.4O2Cl1.4. The unlocked larger surface area, rich bimetallic active sites, and faster carrier dynamics within Pb0.6Bi1.4O2Cl1.4 layers significantly enhance the photocatalytic efficiency for atmospheric CO2 reduction. It outperforms the corresponding parental matrix phase and other state-of-the-art bismuth-based monometallic oxyhalides photocatalysts. This work reports a top-down desalination strategy to engineering ultrathin bimetallic 2D material for photocatalytic atmospheric CO2 reduction, which sheds light on further constructing other ultrathin 2D catalysts for environmental and energy applications from similar complicate structure matrixes.

Electron transfer behaviour of ternary Fe-Zn-F active phase and its enhancement of hydrodesulfurization activity of DBT

In this work, a ternary hydrodesulfurization catalyst with fluorine introduced into the FeZn bimetallic active sites was prepared by a step-by-step incipient wetness impregnation. Among them, the sulfur removal ability increases gradually with the addition of F, and then tends to remain constant. Compared with FeZn catalyst, the maximum activity of the fluorinated catalyst can increase to 6 times at 613 K. It is found that the synergy effect exists in the ternary FeZnF species according to the characterization results. As a part of the active phase, not only the acidity of the catalyst was improved and the dispersion of metal species was optimized by F, but also the closed cycle of complex electron transfer among Fe-Zn-F was aggravated resulting in the weaken of Fe-O/Fe-S bond. Therefore, the sulfurization degree of FeZnF(x) was improved which leads to more active sites and noteworthy HDS activity.

Electronic modulation of iridium-molybdenum oxides with a low crystallinity for high-efficiency acidic oxygen evolution reaction

The development of high-efficiency and stable acidic oxygen evolution reaction (OER) is of great importance toward overall water splitting but challenging. Here, we report the electronic modulation of iridium oxides through the introduction of molybdenum to boost the OER performance in an acidic electrolyte. Remarkably, the prepared iridium-molybdenum oxide (IrMoOx) nanofibers with a low crystallinity through an electrospinning-calcination strategy show a superior OER activity in an acidic electrolyte with a low overpotential of 267 mV at 10 mA cm−2 compared with bare IrOx (333 mV) and MoOx (almost no OER activity) as well as the benchmark commercial IrO2 catalyst (330 mV). Furthermore, the IrMoOx nanofibers catalyst exhibits an excellent long-term stability with a slight degradation of the current density after 30 h because of the strong electronic interactions between IrOx and MoOx components. Furthermore, an overall water splitting device assembled with IrMoOx and Pt/C as electrodes delivers a cell voltage of 1.54 V at 10 mA cm−2 and desirable long-term stability, much better than Pt/C||IrO2 electrolyzer (1.66 V). This work offers a simple and efficient route to fabricate metal oxide-based electrocatalysts with bimetallic active sites, presenting a synergistic enhanced OER performance at a low pH circumstance.

Bimetallic catalyst derived from copper cobalt carbonate hydroxides mediated ZIF-67 composite for efficient hydrogenation of 4-nitrophenol

4-nitrophenol (4-NP), a toxic pollutant, is ubiquitous in the environment and difficult to degrade in natural conditions. To deal with this contaminant, catalytic reduction of 4-NP is a promising way. Herein, we report a copper and cobalt nanoparticle decorated carbon framework (Cu/Co@CF) through a self-sacrificial template method derived from the copper cobalt carbonate hydroxides/zeolitic imidazolate framework-67 (CuCoCH/ZIF-67) composite. Served as a cobalt and copper source as well as a self-sacrificial template, CuCoCH extended the pore sizes of carbonized derivatives of ZIF-67 and synchronously transformed to bimetallic active sites. The catalyst exhibited a highly efficient catalytic performance and remarkable reusability for hydrogenation of 4-NP. The 4-NP conversion reached 99.7% in 1 min and the pseudo-first-order reaction kinetic constant was 5.122 min-1, which is the highest among similarly reported catalysts.

Deactivation mechanism and regeneration effect of bi-metallic Fe-Ni/ZSM-5 catalyst during biomass catalytic pyrolysis

Catalyst deactivation by coke deposition is the main obstacle in the catalytic pyrolysis of biomass. In this study, catalytic pyrolysis of poplar sawdust has been performed in a fixed bed reactor and pyrolysis–gas chromatography/mass spectroscopy (Py-GC/MS) over fresh and regenerated bi-metallic Fe-Ni/ZSM-5 catalysts in order to evaluate the catalytic deactivation process and regeneration effects. The incorporation of Fe and Ni into ZSM-5 promoted deoxygenation activity and hydrocarbon yield. The deoxygenation activity of the catalyst gradually decreased with increasing cumulative biomass/catalyst ratio. At the cumulative biomass/catalyst ratio of 4, the catalyst appears to be completely deactivated, as evidenced by a decrease in the hydrocarbon yield. The coke resistance capacity of bi-metallic Fe-Ni/ZSM-5 was increased due to the stabilizing effect of the bi-metallic active sites. The regenerated catalyst retains deoxygenation activity during the catalytic pyrolysis process, although the aromatic yield (20.85%) was slightly lower than that of the fresh catalyst (21.52%). The physicochemical properties of regenerated catalysts showed that the partial irreversible loss of acidic sites and pore structure are responsible for the slightly reduced activity of the regenerated catalyst. These findings suggest that the bi-metallic Fe-Ni/ZSM-5 catalyst is a promising candidate for industrial application in the field of catalytic pyrolysis.