Catalytic Performance Of Bimetallic Catalysts Research Articles

Fabrication of multiatomic structure of Cu-CoO/Co interface for efficient hydrogen generation from ammonia borane hydrolysis

Hydrogen generation from hydrolysis of ammonia borane is a secure and promising route for conversion of hydrogen energy. Preparation of efficient and economical catalysts is highly required for the development hydrogen economy. In this study, the Co-based catalysts with multiatomic structure were designed for hydrolysis of ammonia borane reaction. The synergistic effect between Co and M (M = Cu, Ni, Fe) greatly enhanced the catalytic performance of bimetallic catalysts. The TOF value of CoCu-NC-5 towards 8.12 min−1 is 7 times that of the single Co catalyst. Moreover, The CoCu catalysts showed the stronger synergistic effect and highest catalytic activity for hydrogen generation, compared with CoNi and CoFe catalysts. The TOF value of CoCu-NC-5 is 2.3 and 6.0 times that of CoFe-NC-5 and CoNi-NC-5 catalysts, respectively. The active component structure of Cu-CoO/Co interface in CoCu-NC-5 is beneficial for activation and dissociation of water molecule due to the strong electron transfer effect and positive synergy. The activation energy over CoCu-NC-5 is 34.25 kJ mol−1, and the catalyst exhibited good stability. This work provides a feasible method for rational design of efficient catalysts with hierarchical structure for conversion of energy.

Enhancing the activity and stability by coupling Ni-M bimetals and TaN for methanol oxidation reaction in alkaline media

Developing the efficient and durable non-platinum based electrocatalysts for methanol oxidation reaction is critical for the application of direct methanol fuel cells (DMFCs). Here, a series of Ni-based catalysts are synthesized via the microwave-assisted ethylene glycol reduction method, which couples the oxyphile metals with transition metal nitrides (TaN), to study the electrocatalytic behavior for methanol oxidation reaction in alkaline media. The results of transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the existence of geometric and electronic effects among Ni, Cu/Sn and TaN. Electrochemical measurements indicate that NiCu-TaN/C and NiSn-TaN/C exhibit high activity with 256.02 and 224.03 mA·cm−2, high surface coverage of redox species, abundant active sites, long-term durability and fast reaction kinetics. In situ ATR-SEIRAS results imply that methanol oxidation reaction mainly goes through the direct pathway on the synthesized catalysts. Combined with the structural characterization and electrochemical measurements, it can be found that the enhanced catalytic performance of bimetallic catalysts can be ascribed to the synergistic effect with coupling the oxyphile metals with TaN. The introduction of Cu/Sn and TaN will change the electronic structure of Ni and coverage of Ni(OH)2/NiOOH redox species on the catalyst surface, which modify the adsorption characteristic of reaction intermediates and formation of HCOO, CO2 and OH species following the direct path in alkaline MOR.

A collaborative diffusion mechanism of multiple atoms during Cu-Ag bimetal surface reconstruction.

The reconstruction of bimetals under reaction conditions is critical for precisely controlling the catalytic performance of bimetallic catalysts. The surface diffusion mechanisms of Cu@Ag nanoparticles before and after CO adsorption were studied in this work. The diffusion patterns with the lowest energy barrier were determined by using ab initio molecular dynamics and meta-dynamics simulations. The effects of nanoparticle size, surface species and CO adsorption were taken into account. We present a mechanism of multiple atom collaborative diffusion during Cu@Ag bimetal reconstruction: surface atoms diffuse outward to form adatoms first, with nearby atoms occupying the original position of the outward diffused atom, and the outward diffusion can accelerate the inward diffusion of nearby surface atoms. The surface diffusion mechanisms of Cu@Ag under a CO atmosphere are different from those of Pd@Au that we previously presented, due to the different diffusion abilities of metal atoms. Our study provides a potential strategy to control the beginning of reconstruction to change the stability of bimetals under reaction conditions.

Surface restructuring in AgCu single-atom alloy catalyst and self-enhanced selectivity toward CO2 reduction

Single atom alloy catalysts, consisting of trace amount of isolated solute atoms alloyed into the host matrix, provide a promising approach to tune the electronic structure and performance of bimetallic catalysts for breaking the limits of scaling relationships based on the unique electronic structures. However, the precisely as-synthesized surface usually suffers from surface evolution leading to activity and durability decay. Herein, the understanding of surface restructuring under reaction conditions is of great importance in optimizing catalytic performance of bimetallic catalysts. In this work, on account of the surface evolution of Cu in electrochemical reactions and its limited miscibility in Ag, a nanoporous AgCu single atom alloy catalyst with atomic ratio Cu:Ag = 1:110 is fabricated by chemical dealloying process. And a CO2-reduction-induced surface restructuring is achieved upon the well-designed catalyst. Noteworthily, nanoporous AgCu exhibits self-reinforcing selectivity toward CO2 reduction and suppressed hydrogen evolution in parallel with migration of Cu to the surface, although the charge transfer from Ag to Cu results in a strong tendency toward hydrogen evolution at the initial catalytic stage. By combining in situ electrochemical hypersensitive response to surface state with ex situ characterizations, the surface reconstruction is verified to be driven by electrochemical reduction of CO2 rather than hydrogen evolution reaction, and can be modulated by the applied potential. Well-reconstructed nanoporous AgCu facilitates the adsorption of CO2. Electronic effect of the restructuring of Cu enhances CO desorption ability on the surface. Consequently, electronic and geometric effects synergically lead to excellent performances with CO Faradaic efficiency of 97.5%. The insights gained from the reconstruction-induced self-reinforcing behavior of bimetallic electrocatalyst shall offer an avenue to rationally design bimetallic electrocatalysts for electrochemical CO2 reduction.

Enhancement of catalytic performance of graphene supported Pt catalysts by Ni and W for hydrogen gas production by hydrothermal gasification of biomass-derived compounds

A more practical approach to reduce the cost of the precious metal catalysts is to replace some of the precious metal particles with non-expensive metals that do not cause considerable loss of catalytic performance. In the present study, Ni and W metal particles deposited on graphene support along with and without Pt particles by ultrasound-assisted wet impregnation that followed chemical and thermal reduction process. The catalytic activities of the resulted catalysts were evaluated by aqueous-phase reforming (APR), an hydrothermal gasification process using glucose solution as feed. Although metal particles on Ni-based catalysts were well dispersed on the support, they had larger particle sizes with a broader size distribution compared to W-based catalysts. The combination of Ni and W metals with Pt showed positive synergy and the catalytic performance of bimetallic catalysts significantly enhanced for conversion of glucose to hydrogen.

MOF derived bimetallic CuBi catalysts with ultra-wide potential window for high-efficient electrochemical reduction of CO2 to formate

Bimetallic electrocatalysts have been proved to be an effective approach to improve the activity and selectivity of electrochemical reduction reaction of CO2 (CO2RR) to formate. However, the activity of catalyst and selectivity of formate are still unsatisfactory. Herein, the rod-like CuBi bimetallic catalysts were synthesized by carbonization and oxidation of CuBi-MOF precursors. Owing to the formation of Bi2CuO4 in the interface of catalyst, the activity and selectivity of the bimetallic CuBi catalysts were greatly enhanced, showing an allured high FEformate of 100 % at −0.77 V (vs. RHE), ultra wide potential window of 900 mV, and excellent durability in H-cell. The in-situ FT-IR and DFT calculation demonstrated that the HCOO* pathway was dominant. Bi2CuO4 can boost the CO2 molecules adsorption capacity and enhance the charge transfer capacity, which benefit its activity and formate selectivity for CO2RR. This work offers insights in improving the catalytic performance of bimetallic catalysts for CO2RR.

Catalytic activity of Ni‐Co supported metals in carbon dioxides methanation

AbstractThis work deals with the catalytic performance of nickel‐cobalt supported on ceria‐doped gadolinia (GDC) catalyst in the single and in the simultaneous methanation of carbon monoxide and carbon dioxide. The catalysts have been prepared by impregnation method, starting from metal salts precursors. Samples have been characterized by x‐ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA‐DSC), hydrogen temperature programmed reduction (TPR‐H2), transmission electronic microscopy (TEM), and scanning electron microscopy (SEM/EDX) technique. The temperature examined for methanation tests ranged from 200°C‐600°C. The results show that the prepared and optimized catalysts possess the main characteristics of materials suitable for SOECs (solid oxide electrolyzer cells) applications: high metal content (50% wt/wt with respect to the support), high activity, and high stability. The catalytic performance of bimetallic catalysts highlights that the cobalt does not improve the activity of the nickel catalysts.

Highly Dispersed Ni–Fe Alloy Catalysts on MgAl2O4 Derived from Hydrotalcite for Direct Ethanol Synthesis from Syngas

In view of the dual active sites mechanism of direct ethanol synthesis and the excellent catalytic performance of bimetallic catalysts, a series of Ni–Fe alloy catalysts with different Ni/Fe molar ratios derived from layered double hydroxides (LDHs) precursors are synthesized. During the calcination and reduction process of LDHs precursors, the Ni–Fe alloy is obtained, and attributed to all the elements being evenly dispersed at the atomic level in the LDHs precursors; meanwhile, a strong interaction between Ni–Fe alloy and MgAl2O4 support exists. As a result, Ni–Fe alloy nanoparticles are highly dispersed on the MgAl2O4 surface. The high CO adsorption ability on the Ni–Fe alloy and synergism catalysis between Ni and Fe result in excellent catalytic activity and high selectivity to ethanol on the bimetallic Ni–Fe alloy. In addition, the strong antisintering ability and stable alloy structure bring about a good catalytic stability. This research proposes a new catalytic system for direct ethanol synthesis from syngas.

Size-Dependent Segregation Preference in Single-Atom Alloys of Late Transition Metals: Effects of Magnetism, Electron Correlation, and Geometrical Strain

Dispersing isolated active metal atoms onto the surface of “inert” metal nanoparticles proves to be particularly effective in improving the catalytic performance of bimetallic catalysts. In this co...

Enhanced Liquid Fuel Production from CO2 Hydrogenation: Catalytic Performance of Bimetallic Catalysts over a Two‐Stage Reactor System

AbstractA bimetallic catalyst combining Fe and Co active sites enables direct conversion of CO2 to hydrocarbons with a higher activity but modest CO selectivity compared with a sole Fe catalyst. The introduction of cobalt metal increases the adsorption ability of CO2, which promotes the CO2 activation over iron species through RWGS reaction. Besides, the carbide content (Fe5C2) also increases significantly with the further introduction of cobalt metal in comparison to potassium modified one, achieving a high C−C bond coupling activity. On the basis, the catalytic performance of CO2 hydrogenation over this bimetallic catalyst was investigated in a two‐stage reactor system, where the influence of number of reactors on CO2 conversion and the catalytic performance over each reactor were analysed regarding the yield of liquid fuel. A significant increase in liquid fuel production was achieved under ordinary conditions. It was proven that ex situ water removal plays the determining role in the integrated process for improving the catalytic activity and lowering the selectivity of undesired CO by‐product. The utilization of a two‐stage reactor system promotes CO2 conversion, making the CO2 conversion approaching a higher value (69.9%). Meanwhile, the yield of liquid fuel exceeds 300 gfuels/(kgcath) under conventional conditions.

Selective hydrogenation of 1,3-butadiene in presence of 1-butene under liquid phase conditions with NiPd/Al2O3 catalysts

The catalytic performance of Al2O3-supported monometallic and bimetallic catalysts in selective hydrogenation of 1,3-butadiene in the presence of 1-butene under liquid phase conditions was studied. Bimetallic catalysts were prepared by the coimpregnation method with the required amounts of the precursors salts [Ni(NO3)2·6H2O and Pd(NH3)4Cl2·H2O] over pellet-form γ-Al2O3 with a constant content of Pd (0.5 wt%) and varying Ni/Pd atomic ratio (0.25, 0.5, 0.75, and 1) obtaining egg-shell profiles of the active components. The catalysts were characterized by X-ray diffraction, temperature-programmed techniques, such as reduction in hydrogen and desorption of ammonia, N2 physisorption, and transmission electron microscopy. The catalytic test showed that the 1,3-butadiene was selectively hydrogenated when bimetallic catalysts were used. The addition of Ni to the Pd-based catalysts suppressed n-butane formation and increased recovery of 1-butene at medium conversion. Therefore, it was observed an improved catalytic performance of the bimetallic catalysts being highest in the case of the 1NiPd/Al2O3.

Optimal Co–Ir bimetallic catalysts supported on γ-Al2O3 for hydrogen generation from hydrous hydrazine

A series of γ-Al2O3 supported bimetallic catalysts CoIrx/γ-Al2O3 was prepared by wet impregnation method followed by air calcination and hydrogen reduction. The catalysts were characterized by using AAS, FTIR, XRD, N2 physisorption, TPR, TPO, and SEM equipped with EDX which show the formation of Co–Ir nanoalloy particles well dispersed on γ-Al2O3 support. The catalytic activity was studied for the decomposition of hydrazine hydrate to generate hydrogen at room temperature and gaseous products were analyzed on mass spectrometer. High catalytic performance of bimetallic catalysts, CoIrx/γ-Al2O3, resulted due to the promoting effect of Ir metal. The optimum composition of CoIr0.081/γ-Al2O3 catalyst exhibited 100% H2 selectivity with TOF of 27.76 h−1. The catalytic activity was further tested at various temperatures to calculate kinetic parameters. The observed activation energy (40.8 kJ mol−1) for CoIr0.081/γ-Al2O3 catalyst reflected its better activity for hydrogen generation when compared to Co/γ-Al2O3 (51.9 kJ mol−1) alone. Hence, CoIr0.081/γ-Al2O3 catalyst is selected as an optimal composition for the hydrogen generation from hydrous hydrazine at room temperature.