Synergetic bimetallic catalysts:A remarkable platform for efficient conversion of CO_(2) to high value-added chemicals

Carbon dioxide reduction reaction(CO_(2)RR) represents an efficient approach to achieving carbon neutrality and simultaneously generating clean energy.However,the strong stability of CO_(2) molecules and the diversity of products pose significant challenges.As an emerging material,bimetallic catalysts have been widely reported for their unique advantages,such as tunable electronic structures,suitable adsorption/desorption of CO_(2) and intermediates,and optimizable d-band centers of active sites through bimetallic synergy.These catalysts provide a remarkable platform for converting CO_(2) into high value-added chemicals.This review comprehensively summarizes recent research advances in bimetallic catalysts for CO_(2)RR.Firstly,the challenges associated with CO_(2)RR,including activity and selectivity are analyzed,followed by a discussion on the unique advantages of bimetallic catalysts.Next,their synthesis strategies are categorized into dual-atom site catalysts(DACs),bimetallic nanoparticles and nanoclusters,binary metal semiconductors,and layered double hydroxides(LDHs).Additionally,advanced characterization techniques of bimetallic catalysts and their applications in CO_(2)RR are thoroughly introduced.Finally,the prospects and challenges for the application of bimetallic materials are highlighted.This review aims to provide inspiration for CO_(2)RR into high-value chemicals and shed light on the research of bimetallic materials.

Bimetallic catalysts as electrocatalytic cathode materials for the oxygen reduction reaction in microbial fuel cell:A review

Microbial fuel cell(MFC) is one synchronous power generation device for wastewater treatment that takes into account environmental and energy issues, exhibiting promising potential. Sluggish oxygen reduction reaction(ORR) kinetics on the cathode remains by far the most critical bottleneck hindering the practical application of MFC. An ideal cathode catalyst should possess excellent ORR activity, stability, and costeffectiveness, experiments have demonstrated that bimetallic catalysts are one of the most promising ORR catalysts currently. Based on this, this review mainly analyzes the reaction mechanism(ORR mechanisms, synergistic effects), advantages(combined with characterization technologies), and typical synthesis methods of bimetallic catalysts, focusing on the application effects of early Pt-M(M = Fe, Co, and Ni) alloys to bifunctional catalysts in MFC, pointing out that the main existing challenges remain economic analysis, long-term durability and large-scale application, and looking forward to this. At last, the research trend of bimetallic catalysts suitable for MFC is evaluated, and it is considered that the development and research of metal-organic framework(MOF)-based bimetallic catalysts are still worth focusing on in the future, intending to provide a reference for MFC to achieve energy-efficient wastewater treatment.

Activity and Selectivity of Bimetallic Catalysts Based on SBA-15 for Nitrate Reduction in Water

Nitrate from the application of nitrogen-based fertilizers in intensive agriculture is a notorious waste product, though it lacks cost-effective solutions for its removal from potential drinking water resources. Catalytic reduction appears to be a promising technique for converting nitrates to benign nitrogen gas. Mesoporous silica SBA-15 is a frequently used catalyst support that has large surface areas and highly ordered nanopores. In this work, mesoporous silica SBA-15 bimetallic catalysts for nitrate reduction were investigated. The catalyst was optimized for the selection of promoter metal (Sn and Cu), noble metal (Pd and Pt) and loading ratios of these metals at different temperatures and reduction conditions. The catalysts prepared were characterized by FT-IR, N2 physisorption, XRD, SEM, and ICP. All catalysts showed the presence of cylindrical mesoporous channels and uniform pore structures that remained even after metals loading. In the presence of a CO2 buffer, the catalysts 4Pd-1Cu/SBA-15 and 1Pt-1Cu/SBA-15 reduced at 100?C under H2 and 1Pd-1Cu/SBA-15 reduced at 200°C under H2 demonstrated very high nitrate conversion. Furthermore, the forementioned Pd catalysts had higher N2 selectivity (88% - 87%) compared to Pt catalyst (80%). Nitrate conversion by the 4Pd-1Cu/SBA-15 catalyst was significantly decreased to 81% in the absence of CO2.

In-situ constructing Cu_(1)Bi_(1)bimetallic catalyst to promote the electroreduction of CO_(2)to formate by synergistic electronic and geometric effects

Electrochemical CO_(2)reduction to formate is a potential approach to achieving global carbon neutrality.Here,Cu1Bi1bimetallic catalyst was prepared by a co-precipitation method.It has a ginger like composite structure(CuO/CuBi_(2)O_(4))and exhibited a high formate faradaic efficiency of 98.07%at–0.98 V and a large current density of–56.12 mA.cm^(-2)at–1.28 V,which is twice as high as Bi2O3catalyst.Especially,high selectivity(FE^(–)_(HCOO)>85%)is maintained over a wide potential window of 500 mV.In-situ Raman measurements and structure characterization revealed that the reduced Cu1Bi1bimetallic catalyst possesses abundant Cu-Bi interfaces and residual Bi-O structures.The abundant Cu-Bi interface structures on the catalyst surface can provide abundant active sites for CO_(2)RR,while the Bi-O structures may stabilize the CO_(2)^(*–)intermediate.The synergistic effect of abundant Cu-Bi interfaces and Bi-O species promotes the efficient synthesis of formate by following the OCHO^(*)pathway.

Long-range electron synergy over Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst in enhancing charge separation for photocatalytic hydrogen production

The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.

Conjugated polymerized bimetallic phthalocyanine based electrocatalyst with Fe-N_(4)/Co-N_(4) dual-sites synergistic effect for zinc-air battery

The bifunctional oxygen catalyst is essential for zinc-air batteries(ZABs).Here,an efficient bifunctional oxygen catalyst,PPcFeCo/3D-G,is obtained throughπ-πinteraction between the conjugated polymerized iron-cobalt phthalocyanine(PPcFeCo)with excellent thermal stability and three-dimensional graphene(3D-G).The bimetallic synergistic effect of PPcFeCo,verified by DFT(Density functional theory)calculation,andπ-πinteractions enhances the catalytic activity and durability of the PPcFeCo/3D-G.Regarding electrochemical performance,the PPcFeCo/3D-G with a high electron transfer number(3.98,@0.768 V vs.RHE)has excellent half-wave potential(E_(1/2)=0.890 V vs.RHE)and exhibits outstanding reversibility(ΔE=0.700 V,ΔE=Ej=10-E_(1/2)).The liquid ZAB(LZAB)employed PPcFeCo/3D-G displays a high power density(222 m W cm^(-2)),a specific capacity(792 m A h g-1),and excellent durability(120 h).This work has guiding significance for the preparation of high-efficiency bifunctional catalysts.

Reactive ball-milling synthesis of Co-Fe bimetallic catalyst for efficient hydrogenation of carbon dioxide to value-added hydrocarbons

Catalytic hydrogenation of CO_(2) using renewable hydrogen not only reduces greenhouse gas emissions,but also provides industrial chemicals.Herein,a Co-Fe bimetallic catalyst was developed by a facile reactive ball-milling method for highly active and selective hydrogenation of CO_(2) to value-added hydrocarbons.When reacted at 320℃,1.0 MPa and 9600 mL h^(-1) g_(cat)^(-1),the selectivity to light olefin(C_(2)^(=)-C_(4)^(=)) and C_(5)+ species achieves 57.3% and 22.3%,respectively,at a CO_(2) co nversion of 31.4%,which is superior to previous Fe-based catalysts.The CO_(2) activation can be promoted by the CoFe phase formed by reactive ball milling of the Fe-Co_(3)O_(4) mixture,and the in-situ Co_(2)C and Fe_(5)C_(2) formed during hydrogenation are beneficial for the C-C coupling reaction.The initial C-C coupling is related to the combination of CO species with the surface carbon of Fe/Co carbides,and the sustained C-C coupling is maintained by self-recovery of defective carbides.This new strategy contributes to the development of efficient catalysts for the hydrogenation of CO_(2) to value-added hydrocarbons.

Highly effective direct synthesis of DMC from CH_3OH and CO_2 using novel Cu-Ni/C bimetallic composite catalysts

Novel Cu-Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH_3OH and CO_2.

Atomically Dispersed Fe-Co Bimetallic Catalysts for the Promoted Electroreduction of Carbon Dioxide

The electroreduction reaction of CO_(2)(ECO_(2)RR)requires high-performance catalysts to convert CO_(2)into useful chemicals.Transition metal-based atomically dispersed catalysts are promising for the high selectivity and activity in ECO_(2)RR.This work presents a series of atomically dispersed Co,Fe bimetallic catalysts by carbonizing the Fe-introduced Co-zeolitic-imidazolate-framework(C-Fe-Co-ZIF)for the syngas generation from ECO_(2)RR.The synergistic effect of the bimetallic catalyst promotes CO production.Compared to the pure C-Co-ZiF,C-Fe-Co-ZIF facilitates CO production with a CO Faradaic efficiency(FE)boost of 10%,with optimal FE_(CO)of 51.9%,FE_(H_(2))of 42.4%at-0.55 V,and CO current density of 8.0 mA cm^(-2)at-0.7 V versus reversible hydrogen electrode(RHE).The H_(2)/CO ratio is tunable from 0.8 to 4.2 in a wide potential window of-0.35 to-0.8 V versus RHE.The total FE_(CO+H_(2))maintains as high as 93%over 10 h.The proper adding amount of Fe could increase the number of active sites and create mild distortions for the nanoscopic environments of Co and Fe,which is essential for the enhancement of the CO production in ECO_(2)RR.The positive impacts of Cu-Co and Ni-Co bimetallic catalysts demonstrate the versatility and potential application of the bimetallic strategy for ECO_(2)RR.

Synergistic effects of bimetallic Cu-Fe/SiO_2 nanocatalysts in selective hydrogenation of diethyl malonate to 1,3-propanediol

Cu_x-Fe_y/SiO_2 catalysts were prepared using urea-assisted sol-gel method.The structure and physicochemical properties of the catalysts were characterized using N_2 adsorption-desorption,transmission electron microscopy,H_2-temperature-programmed reduction,powder X-ray diffraction,and X-ray photoelectron spectroscopy.Compared with monometallic Cu or Fe catalysts,the bimetallic Cu_x-Fe_y/SiO_2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to1,3-propanediol.The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity,which yielded 96.3%conversion to diethyl malonate and 93.3%selectivity to 1,3-propanediol under the optimal reaction conditions.Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol.The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu^(2+) species,thereby increasing the Cu° species on the surface of bimetallic catalyst.It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule.The ethyl acetate temperature-programmed desorption results indicated that the FeO_x species provided the additional adsorption sites for substrate molecules,and they activated the C=O bond.The improved catalytic performance of bimetallic Cu_x-Fe_y/SiO_2 catalyst was mainly attributed to the synergistic effect between Cu° and FeO_x species.

Boosting the water gas shift reaction on Pt/CeO_(2)-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying

The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells.The influence of support doping and bimetallic alloying on the catalytic performance of Pt/Ce O_(2)-based nanocatalysts in water gas shift reaction was reported in this work.Various lanthanide ions and 3d transition metals were respectively introduced into the Ce O_(2)support or Pt to form Pt/Ce O_(2):Ln(Ln=La,Nd,Gd,Tb,Yb)and Pt M/Ce O_(2)(M=Fe,Co,Ni)nanocatalysts.The sample of Pt/Ce O_(2):Tb showed the highest activity(TOF at 200℃=0.051 s^(-1))among the Pt/Ce O_(2):Ln and the undoped Pt/Ce O_(2)catalysts.Besides,the sample of Pt Fe/Ce O_(2)exhibited the highest activity(TOF at 200℃=0.12 s^(-1))among Pt M/Ce O_(2)catalysts.The results of the multiple characterizations indicated that the catalytic activity of Pt/Ce O_(2):Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support.However,the different activity of Pt M/Ce O_(2)bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria.The study of the reaction pathway indicated that both the samples of Pt/Ce O_(2)and Pt/Ce O_(2):Tb catalyzed the reaction through the formate pathway,and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation.As for the sample of Pt Fe/Ce O_(2),its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.

Base-free aerobic oxidation of glycerol on TiO_2-supported bimetallic Au–Pt catalysts

The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au–Pt, Au–Pd and Pt–Pd catalysts on Ti O2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au–Pd and Pt–Pd while Au was essentially inactive. The presence of Au on the Au–Pt/Ti O2 catalysts led to their higher activities(normalized per Pt atom) in a wide range of Au/Pt atomic ratios(i.e.1/3–7/1), and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile,the presence of Au on Au–Pt/Ti O2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.

Utilizing bimetallic catalysts to mitigate coke formation in dry reforming of methane

Dry reforming of methane(DRM) involves the conversion of carbon dioxide(CO_(2)) and methane(CH_(4)) into syngas(a mixture of hydrogen, H_(2), and carbon monoxide, CO), which can then be used to produce a wide range of products by means of Fischer–Tropsch synthesis. DRM has gained much attention as a means of mitigating damage from anthropogenic greenhouse gas(GHGs) emissions to the environment and instead utilizing these gases as precursors for value-added chemicals or to synthesize sustainable fuels and chemicals. Carbon deposition or coke formation, a primary cause of catalyst deactivation, has proven to be a major challenge in the development of DRM catalysts. The use of nickel-and cobalt-based catalysts has been extensively explored for DRM for their high activity and low cost but suffer from poor stability due to coke formation that has hindered their commercialization. Numerous articles have reviewed the various aspects of catalyst deactivation and strategies for mitigation, but few has focused on the benefit of bimetallic catalysts for mitigating coke formation. Bimetallic catalysts, often improve the catalytic stability over their monometallic counterparts due to synergistic effects resulting from two metal-tometal interactions. This review will cover DRM literature for various bimetallic catalyst systems, including the effect of supports and promoters, on the mitigation of carbonaceous deactivation.

Reverse Microemulsion Synthesis and Characterization of Pd-Ag Bimetallic Alloy Catalysts Supported on Al_2O_3 for Acetylene Hydrogenation

Pd-Ag bimetallic alloy nanoparticles were synthesized by the reverse microemulsion method,and then deposited on Al2O3 to form the supported catalyst.The nanoparticles of Pd-Ag and Pd-Ag/Al2O3 samples were characterized by UV/Vis,HRTEM,EDX,XRD,and XPS.The test results indicated that Pd-Ag bimetallic alloy nanoparticles with a size of about 2 nm and a face-centered cubic(fcc) structure were formed in the measured area of microemulsion.The growth of nanoparticles was effectively limited within the droplet of micoremulsion.TEM image exhibited that the Pd-Ag alloy nanoparticles were well-dispersed on the Al2O3 support.The catalytic performance of various catalysts for selective hydrogenation of acetylene showed that a higher acetylene conversion and selectivity to ethylene upon acetylene hydrogenation was achieved on a nano-sized Pd-Ag bimetallic catalyst with a Pd/Ag alloy supported molar ratio of 1:1.5.

Hydrodeoxygenation of Bio-Oil on Bimetallic Catalysts: From Model Compound to Real Feed

Two series of bimetallic Ni-Co catalysts and corresponding monometallic catalysts with ca. 20 wt% metal loading were evaluated in hydrodeoxygenation (HDO) of phenol as a model compound for bio-oil. The bimetallic catalysts outperformed the corresponding monometallic catalyst in terms of conversion and cyclohexane selectivity. This could be attributed to the formation of Ni-Co alloy, which caused a decrease in metal particle size and stabilized Ni active sites in the near surface region. The balanced combination of formed Ni-Co alloy with acidity from supports allowed performing all individual steps in the reaction network toward desired products at high rate. Consequently, the two best-performing catalysts were tested in HDO of wood based bio-oil, showing that the bimetallic catalyst 10Ni10Co/HZSM-5 was more effective than 20Ni/HZSM-5 in terms of degree of deoxygenation and upgraded bio-oil yield. These findings might open an opportunity for development of a novel cheap but effective catalyst for a key step in the process chain from biomass to renewable liquid fuels.

Activity and Selectivity in CO Hydrogenation with Silica-supported Ru-Co Bimetallic Cluster-derived Catalysts

The catalytic performance of bimetallic Ru-Co catalysts prepared from a series of H3Ru3Co(CO)12. RuCo2(CO)11 and HRuCo3(CO)12 in CO hydrogenation was investigated, and it was found that the Ru-Co bimetallic carbonyl cluster-derived catalysts showed a high activity for products, particularly higher oxygenates, compared with the catalysts prepared from impregnation or co-impregnation of monometallic clusters such as [HRu3(CO)11] and Co4(CO)12. The selectivity for oxygenates in CO hydrogenation highly increased with the molar ratio of Co/Ru in the Ru-Co bimetallic cluster to CO/H2 in feed gas. Raising reaction temperature led to an intensive increase of CO conversion and a considerable decrease of selectivity for oxygenates. In situ FT-IR studies revealed that the band at 1584 cm-1 on Ru-Co bimetallic cluster-derived catalysts at 453 K under syngas (CO/H2 = 0. 5) has a good linear relationship to rates of oxygenate formation, which is likely associated with an intermediate to produce oxygenates in CO

STUDY ON POLYMER—Ru-Co—BIMETALLIC COMPLEXES CATALYSTS Ⅰ. SYNTHESIS OF CATALYSTS AND THEIR USE FOR THE HYDROFORMYLATION

Six kinds of polymer ligands, supported on SiO2, containing coordinating atoms P, S and N respectively, have been synthesized. The Ru（Ⅲ）-Co（Ⅱ） bimetallic complexes of these polymer ligands have been obtained and examined as catalysts for the hydroformylation of cyclohexene. The effects of reaction temperature, pressure and Co/Ru ratio etc. on the activities of catalysts were investigated in detail. The catalysts are all polymer-noncarbonyl-metal complexes, easily to be prepared, active and stable. From the experimental results it can be suggested that under reaction conditions such polymer-noncarbonyl-metal complexes convert "in situ" to polymer-carbonyl-metal complexes, thus become active catalysts. The course of this conversion is supposed as a preliminary approach.

Performance Comparison of Two Newly Developed Bimetallic(X-Mo/Al2O3, X=Fe or Co) Catalysts for Reverse Water Gas Shift Reaction

The performance of the two newly developed bimetallic catalysts based on the precursor, Mo/Al_2O_3, was compared for reverse water gas shift(RWGS) reaction. The structures of the precursor and the catalysts were studied using X-ray diffraction(XRD), Brunauer–Emmett–Teller(BET) analysis, inductively coupled plasma-atomic emission spectrometry(ICP-AES), CO chemisorption, temperature programmed reduction of hydrogen(H_2-TPR) and scanning electron microscopy(SEM) techniques. The activity of Fe-Mo and Co-Mo catalysts was compared in a fixed bed reactor at different temperatures. It is shown that the Co-Mo catalyst has higher CO_2 conversion at all temperature level. The time-on-stream(TOS) analysis of the activity of catalysts for the RWGS reaction was carried out over a continuous period of 60h for both catalysts. The Fe-Mo/Al_2O_3 catalyst exhibits good stability within a period of 60h, however, the Co-Mo/Al_2O_3 is gradually deactivated after 50h of reaction time. Existence of(Fe_2(MoO4_))_3 phase in Fe-Mo/Al_2O_3 catalyst makes this catalyst more stable for RWGS reaction.

Preparation and Characterization of Macroporous Resin Immobilized Pd－Cu Bimetallic Cluster Catalysts

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PVP-Supported Palladium-Cadmium Bimetallic Catalyst for the Hydrogen Transfer Dechlorination of Aryl Chlorides

PVP-supported bimetallic catalyst- PVP-PdCl2-CdCl2, exhibits extremely high catalytic activity for the hydrogen transfer dechlorination of aryl chlorides in neutral environment. The yields of dechlorination products are high under mild reaction conditions and the operation is