Bimetallic Catalysts Research Articles

Cu−Bi Bimetallic Catalysts Derived from Metal–Organic Framework Arrays on Copper Foam for Efficient Glycine Electrosynthesis

AbstractGlycine as one of the most abundant amino acids in human proteins, with extensive applications in both life and industry, is conventionally synthesized through complex procedures or toxic feedstocks. In this study, we present a facile and benign electrochemical pathway for synthesis of glycine through reductive coupling of glyoxylic acid and nitrate over a copper‐bismuth bimetal catalyst derived from a metal–organic framework (MOF) array on copper foam (Cu/Bi−C@CF). Remarkably, Cu/Bi−C@CF achieves a fantastic selectivity of 89 %, corresponding a high Faraday efficiency of 65.9 %. From control experiments, the introduction of Bi caused the binding energy of Cu shift to a lower state, which leads to a high selectivity towards the formation of key intermediate hydroxylamine rather than ammonia product, facilitating the formation of oxime and providing additional sites for subsequent hydrogenation reaction on the way to glycine. Moreover, the derivation of MOF arrays ensures the effective dispersion of Bi and enhances the stability of Cu/Bi−C@CF. This innovative approach not only presents sustainable pathways for the production of value‐added organonitrogen compounds utilizing readily available carbon and nitrogen sources, but also provides novel insights into the design of multistage structural catalysts for sequential reactions.

Enantioselective Construction of Oxindoles Bearing a Quaternary Carbon via Ni−Al Bimetal‐Catalyzed Formyl C−H Alkylation

AbstractEnantioselective transition metal‐catalyzed C−H alkylation emerges as one of the most atom‐ and step‐economical routes to chiral quaternary carbons, while big challenges still remain with acyl C−H alkylations. Herein, we use a Ni−Al bimetallic catalyst to facilitate a highly regioselective and highly enantioselective C−H alkylation of formamides with alkenes, constructing various oxindoles bearing a chiral quaternary carbon in up to 94 % yield and up to 95 % ee.

Influence of Dopants on Pt/Al2O3-Based Monolithic Catalysts for Autothermal Oxidative Coupling of Methane

Autothermal oxidative coupling of methane (OCM) is a highly attractive approach for methane utilization. If platinum-based catalysts are operated in short-contact-time reactors with high space velocities, high methane conversion can be achieved. Using a 1 wt.% Pt/Al2O3 catalyst as a benchmark, the present study elucidates how different dopants, namely Ni, Sn, and V2O5, affect the OCM reaction. Kinetic catalyst tests reveal that acetylene (C2H2) is the predominant C2 product, irrespective of the catalyst formulation or operation conditions. Furthermore, the use of bimetallic catalysts allows either for the maintenance or even the improvement of the C2 selectivity during OCM, which is attributed to synergistic effects that occur when expensive Pt is partially replaced by cheaper dopants. In particular, the 1 wt.% Pt/Al2O3 reference catalyst yielded a maximum C2 selectivity of 8.2%, whereas the best-performing doped sample 0.25 wt.% Pt 0.75 wt.% V2O5/Al2O3 yielded a total C2 selectivity of 11.3%.

Revealing the Potential of Bimetallic Carbide Catalysts for Upgrading Biomass‐derived Bio‐Oil: A First Principles‐Based Investigation Using Representative Bio‐oil Constituents

Bimetallic carbides, especially based on molybdenum carbide, proved to be a promising hydrodeoxygenation (HDO) catalyst, with enhanced selectivity towards C – O bonds cleavage. However, catalysts are generally investigated using limited model components derived from only one of the biopolymers in biomass (either lignin or carbohydrates), therefore, HDO of raw biomass‐derived bio‐oil still remains a challenge, as it contains molecules of different functionalities. This paper presents a systematic comparison of the monometallic carbide, Mo2C, with the novel bimetallic carbide incorporating W using representative bio‐oil components of different functionalities and derived from different bio‐polymers components of biomass. We employed quantum mechanical investigation to reveal that the W‐doped Mo2C carbide (MoWC) catalyst with increased oxophilicity, owing to tungsten incorporation, can perform HDO of real bio‐oil more effectively in comparison to its monometallic counterpart (Mo2C) using six substrates representing different components of bio‐oil. We showed MoWC can selectively cleave both single/double (C – O/C = O) bonds with similar barriers in comparison to Mo2C which can only selectively cleave single C – O bonds. This observation was consistent for 5‐HMF, Acetic acid, and Methyl Glyoxal. We also showed that MoWC outperforms its metallic counterpart Mo2C in the HDO for aromatic and carbohydrate components.

Exploring Pt-Cu synergistic effects on porous SiO2 support with different Pt loadings for low-temperature oxidation of CO and C3H6

To address the high cost of noble metals, this study aims to optimize Pt loading and the synergistic effect of Cu on porous SiO2 support for low-temperature oxidation of CO and C3H6. A simulated test bench system was used to evaluate the performance of PtxCu1/SiO2 (where x= 0.3, 0.5, 0.7, and 1 wt%), Cu1/SiO2 and Ptx/SiO2 (where x= 0.5 and 1 wt%) catalysts with varying Pt loadings. Comprehensive characterization, including BET, XRD, SEM, TEM, and XPS was conducted to assess particle size, structure, and surface morphology. The effects of Pt incorporation on reduction and oxidation properties were further examined using H2-TPR and CO-TPD techniques. Results demonstrated a significant enhancement in catalytic activity with the addition of Cu confirming a synergistic interaction between Pt and Cu. This synergy was particularly pronounced in lower Pt loadings, where PtxCu1/SiO2 composites outperformed Ptx/SiO2 in catalytic activity. Pt addition reduced the particle size, which resulted in the creation of PtCu alloy, with 1 and 0.7 % wt Pt loading exhibiting comparable effects in CO conversion and 0.7 % Pt loading exhibiting better activity at higher temperatures in C3H6 oxidation indicating that catalytic activity was maintained even with a reduced Pt loading. Additionally, minimal difference in activity for C3H6 oxidation was observed among PtxCu1/SiO2 catalysts with 0.7, 0.5, and 0.3 wt% Pt loadings as indicated by T50 and T80 values. Reducing Pt loading from 0.7 wt% had minimal impact on catalytic efficiency for C3H6 oxidation with catalysts maintaining high activity. 0.7 wt% Pt loadings provide sufficient active sites for effective CO and HC oxidation. The enhanced catalytic activity and stability of bimetallic catalysts over monometallic Cu/SiO2 and Pt/SiO2 result from the simultaneous presence of active sites created by the synergetic effect of PtCu alloy formation with optimal ratio and well-optimized surface. These findings demonstrate the potential to optimize Pt usage without compromising catalytic performance, offering a cost-effective approach to catalyst design.

Enhanced CO2-to-CH4 conversion via grain boundary oxidation effect in CuAg systems

The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cuδ+ species, is still debatable, and their role in governing CH4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cuδ+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cuδ+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO2-to-CH4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO2-to-CH4 conversion.

Efficient activation of peroxyacetic acid by cobalt-iron alloy/oxide heterojunctions anchored in defect-rich biochar for pesticide degradation in water: Unravelling the radical-unradical mechanism

The activation processes of peracetic acid (PAA-AOPs) have garnered significant attention in wastewater treatment. In this study, an amorphous carbon-modified bimetallic CoFe alloy/oxide catalyst (CoFe@DBCx-y, where x represents biomass mass and y represents pyrolysis temperature) was developed to activate PAA for the degradation of organochlorine pesticides (OCPs). Due to the size effect, biochar dynamically regulates the particle size of metal species, which is influenced by the pyrolysis temperature. Among these systems, the CoFeDBC2.0–700/PAA oxidation system effectively removed 95.7 % of 2,4-dichlorophenoxyacetic acid (2,4-D), exhibiting a kinetic constant 1.7 times higher than that of the Nano/PAA system. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that high-valent metal oxides (MIV = O) and singlet oxygen (1O2) are the primary active species responsible for the removal of 2,4-D, whereas organic radicals (RO·) and hydroxyl radicals (·OH) play a secondary role. Electrochemical and Raman spectroscopy tests revealed the formation of a metastable surface complex (≡Co(III)–OO(O)CCH3) between PAA and the catalyst, which acted as an intermediate oxidant to generate reactive oxygen species (ROS) through a chain reaction. Carbon defects in the biochar functioned as an electron source, continuously replenishing the electrons consumed in the reaction and facilitating the valence cycling between Co and Fe. This study provides new insights into the remediation of pesticide-contaminated wastewater using PAA-AOPs with heterogeneous bimetallic carbon-based catalysts.

Recycling copper wire waste into active Cu-based catalysts for value-added chemicals production via CO2 electrochemical reduction

The CO2 electroreduction reaction (CO2RR) is a method for producing value-added compounds from CO2. This study aimed to use copper from wiring waste to create Cu-based catalysts on Vulcan XC-72R carbon for converting CO2 into valuable chemicals. Copper nanopowder with an average crystallite size of 27 nm derived from the wiring waste solution was utilized as the starting material for mono and bimetallic catalysts preparation. During the bimetallic PdCu/C catalyst synthesis, a galvanic displacement reaction between Pd and Cu occurred, resulting in the formation of PdCu alloy and a reduction in the copper crystallite size. The inclusion of Pd on Cu/C in CO2RR decreased the onset potentials for C1 and C2 chemical production. The yields of methanol, formic acid, and formaldehyde products were generally increased as the Pd:Cu ratio increased. The 1:2-PdCu/C exhibited the smallest crystallite size and an onset potential of less than −1.0 V, resulting in the highest Faradaic efficiency of the products. This catalyst converted CO2 into formic acid (FE = 71.5 %) at a potential of −0.8 V and methanol (FE = 65.4 %) at −0.5 V. The catalyst’s stability was demonstrated for more than 6000 s at current densities of approximately 2 mA mg-1catalyst.

The Effect of Saccharin on SnNi Alloy: the Electrodeposition and its Electrocatalytic Activity in Ethanol Oxidation Reaction

The development of Direct Ethanol Fuel Cell (DEFC) has attracted much attention, as alternative energy sources due to its various advantages. However, among its various advantages, DEFC has several problems, such as the kinetics of the ethanol oxidation reaction. Transition metal-based catalysts such as nickel and tin are considered as potential catalysts for DEFC due to their oxophilic properties that can improve catalytic activity. In this study, the effect of saccharin on SnNi bimetallic alloy catalyst synthesized by electrodeposition method on copper wire substrate was investigated. SnNi samples were characterized by several techniques, including X-ray diffraction, Scanning electron microscopy, and energi dispersive X-ray spectrocopy. Saccharin addition had a significant effect on the morphology, crystallite size, and composition of the catalyst. The presence of saccharin causes the formation of more uniform particles and has a smaller size. The sample with the addition of saccharin had a smaller charge transfer resistance value 4.82 Ω, lower tafel slope by 115 mV/dec, and show higher jf/jb ratio by 0.55. Furthermore, as the current density decreases, the SnNi catalyst with saccharin has a slow decrease rate and higher stability than the SnNi catalyst without saccharin.

Effect of rhenium on the activity of ZrO2-supported copper catalysts for hydrodeoxygenation of m-cresol

This work studies the effect of adding different loadings of Re on the performance of ZrO2-supported Cu catalysts for hydrodeoxygenation (HDO) of m-cresol. H2-TPR and XPS show a synergistic effect between Cu and Re, decreasing the reduction temperature of both metals and promoting the reduction of Re oxide. Moreover, the addition of Re changes Cu dispersion and acid properties of all catalysts. High Re contents results in a coverage of Cu surface. Catalytic tests reveal that HDO reaction rate and product distribution vary considerably depending on the Re loading. Cu catalyst was inactive for HDO reaction, forming only hydrogenation products. In contrast, Re catalyst stood out for its high capacity to promote HDO reaction, with significant production of toluene. For the bimetallic catalysts, the addition of Re increases HDO reaction rate from 0 to 0.39 mmol gmetal−1 min−1 and the selectivity towards toluene (0–82.6 %), whereas the formation of hydrogenation and dehydration products decreases.

Enhancing sulfamerazine degradation via peroxymonosulfate with Fe-doped Mo2C materials: Catalytic performance and mechanistic insights

Sulfonamide antibiotics are a common group of drugs that have the potential to induce the generation of resistance genes even at low concentrations. Herein, a novel Fe3Mo3C/Mo2C/Mo composite (Fe-Mo2C-1.0) was prepared by modifying the synthesis process of Fe-doped Mo2C and used to activate peroxymonosulfate (PMS) to degrade sulfamerazine (SMR). The optimal performance catalyst was obtained at Fe/Mo = 1.0 and a calcination temperature of 900 ℃. Fe-Mo2C-1.0 achieved 98.8 % SMR removal in 20 min, which was 4.5 and 44.3 times higher than that of Fe-Mo2C-0.5/PMS and Mo2C/PMS systems, respectively. In Fe-Mo2C-1.0, multiple low-valent forms of the element Mo, including Mo, Mo(II) and Mo(IV), which are highly reductive, participated in and contributed to the regeneration of Fe(II). The proportion of Fe(II) on the surface of Fe-Mo2C-1.0 before and after the reaction was maintained at a stable level. In addition, the high Fe content and sp2 hybridized carbon in Fe-Mo2C-1.0 promoted the role of mediated electron transfer during catalysis process. Electrochemical characterization indicated that Fe-Mo2C-1.0 had better redox properties, smaller electron transfer resistance and a faster corrosion rate than Fe-Mo2C-0.5 and Mo2C. Other SMR oxidation mechanisms included SO4∙-, O2∙- and 1O2, with 1O2 contributing the most. Finally, three possible degradation pathways of SMR were proposed. This work provided thoughts on the synthesis of Fe/Mo bimetallic carbide catalysts as well as reference for the removal of SMR by PMS activation.

Preparation of NiCo hydroxide by chloride corrosion for electrocatalytic upcycling of polyethylene terephthalate plastic waste

Upcycling plastic waste into value-added chemicals is an innovative strategy that addresses environmental concerns and creates economic value. As one of the polyesters that is widely used, polyethylene terephthalate (PET) plastic waste is employed as the model substrate. Here we report a chloride corrosion method to synthesize bimetallic hydroxide catalysts on nickel foam. By using a nickel–cobalt hydroxide catalyst (NiCo-OH/NF), we demonstrate an electrocatalytic oxidation strategy to transform real-world polyethylene terephthalate (PET) water bottle into potassium formate and terephthalic acid (TPA) with high Faraday efficiency of 92.1 % at 1.40 V vs. RHE. The in situ spectroscopy and theoretical calculations provide insights into the catalytic mechanism especially active sites, pivotal intermediates, and favorable pathways. This work highlights the significant potential of electrochemical conversion as a means of achieving PET upcycling.

Preventing Nitrite Desorption via Switching Hydrogenation Position: A Dual-Site Approach for Selective Nitrate Reduction to Ammonia.

The electrochemical nitrate reduction reaction (NO3RR), which converts harmful nitrates into valuable ammonia (NH3) with zero carbon emission, is one of the most promising alternatives to the Haber-Bosch process. However, the NO3RR process is complex and involves multiple proton-coupled electron transfers that generate intermediates or byproducts, such as NO2 -, resulting in low ammonia yields and faradaic efficiency (FE). Herein, by constructing a FeCu bimetallic catalyst (FeCu-NC), the hydrogenation position of *NO3 is switched at the FeCu dual-atom site, preventing the desorption of *NO2 intermediate. Furthermore, electron transfer from Cu to Fe sites mimics the electron flow direction in natural nitrite reductase enzymes and accelerates the reduction of *NO2 to NH3, achieving efficient conversion of NO3 - to NH3. A 24-hour electrocatalytic experiment with FeCu-NC demonstrates negligible NO2 - formation throughout the NO3RR process, with an ammonia production rate of 6.13mgh-1mgcat -1 and an impressive FE of 95%, which are remarkably superior in comparison to most of the NO3RR electrocatalysts. This work opens new avenues for the fundamental understanding of catalytic mechanisms and the development of next-generation catalysts for sustainable ammonia production.

First-principles study of selective CO2 activation to methanol on PdZn/TiO2: Unveiling Zn/Pd ratio on catalysis performance

In this study, a series of Pd(8-n)Znn/TiO2(n=0–8) were investigated via density functional theory (DFT) to understand the influence of Zn/Pd ratio on their catalysis performance of conversion CO2 to methanol. It is revealed that Zn prefers to replace the bottom-layered Pd when its molar concentration in composition increases. For all surface models, interface between cluster and support plays a key role in CO2 stabilization and activation. Increasing Zn/Pd ratio could weaken the binding strength of CO2 over catalyst, which further hinders the “RWGS” pathway while promotes the “Formate” pathway. Based on the calculation results, a Brønsted–Evans–Polanyi (BEP) relation between the activation barrier (Ea) of key elementary steps from both mechanisms and the binding strength of key intermediates has been established, from which the optimum Zn/Pd ratio leading to the best catalysis performance has been determined. Moreover, it is found that water inclusion in the system does not change the Ea of rate-determining step much even though it has a promotion effect on OH formation steps. Overall, this work provides some meaningful insight into the influence of cluster composition on the catalysis performance of PdZn-based catalyst and provides valuable information about rational design of the supported bimetallic catalyst.

Colloidal Bimetallic RuNi Particles and their Behaviour in Catalytic Quinoline Hydrogenation.

Colloidal metal nanoparticles exhibit interesting catalytic properties for the hydrogenation of (hetero)arenes. Catalysts based on precious metals, such as Ru and Rh, promote this reaction efficiently under mild reaction conditions. In contrast, heterogeneous catalysts based on earth-abundant metals can selectively hydrogenate (hetero)arenes but require harsher reaction conditions. Bimetallic catalysts that combine precious and earth-abundant metals are interesting materials to mitigate the drawbacks of each component. To this end, RuNi nanoparticles bearing a phosphine ligand were prepared through the decomposition of [Ru(η4-C8H12)(η6-C8H10)] and [Ni(η4-C8H12)2] by H2 at 85 °C. Wide angle X-ray scattering confirmed a bimetallic segregated structure, with Ni predominantly on the surface. Spectroscopic analyses revealed that the phosphine ligand coordinated to the surface of both metals, suggesting, as well, a partial Ni shell covering the Ru core. The RuNi-based nanomaterials were used as catalysts in the hydrogenation of quinoline to assess the impact of the metallic composition and of the stabilizing agent on their catalytic performance.

Removal of tetracycline antibiotic from aqueous solution using bimetallic CuCo-ZIFs as an efficient catalyst in the presence of hydrogen peroxide

Antibiotics play an important role in disease treatment; however, they are also a threat to public health and the ecosystem. Therefore, a bimetallic CuCo-ZIFs catalyst was manufactured through the ultrasonic-assisted solvothermal method to activate H2O2 towards the removal of tetracycline (TC) in an aqueous environment, a polluting broad-spectrum antibiotic model. PXRD, SEM, TEM, EDX, TGA, FT-IR, and BET analyses indicated that CuCo-ZIFs cubic crystals were successfully synthesized with high crystallinity, large specific surface area, and ideal thermal stability. Factors affecting the TC removal were investigated, including CuCo-ZIFs dosage, H2O2 concentration, treatment time, initial TC concentration, and reaction temperature. The results showed that the CuCo-ZIFs/H2O2 catalytic system was capable of effectively handling TC, with about 93.9% of TC removed in the presence of 0.3 g.L-1 CuCo-ZIFs, 0.01 mol.L-1 H2O2 at room temperature within 30 min. Conclusively, this study contributes to expanding the application potential of bimetallic CuCo-ZIFs materials to eliminate antibiotic residues in an aqueous environment and inspire research on environmental improvement.

Searching for the optimum Pt loading in bimetallic PtXNi/SBA-15 catalysts for hydrodeoxygenation

AbstractBimetallic PtXNi5/SBA-15 catalysts with 5 wt% Ni and X = 0.1–2.0 wt% Pt were synthesized and characterized. The XPS characterization of bimetallic catalysts showed the presence of oxide Ni2+, Pt2+ and reduced Pt0 species in the calcined catalysts. After the reduction, metallic Ni0 appeared in addition to the above-mentioned species. The proportions of the reduced Ni and Pt increased with increasing Pt content in the catalysts. The presence of metal species of different oxidation states at the Ni–Pt interface was crucial for their catalytic performance in the hydrodeoxygenation of anisole. The Pt0.5Ni5/SBA-15 catalyst was the most active and selective. Graphical abstract

Microwave-Assisted Conversion of 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid over CuCo Oxide.

A series of CuCo bimetallic catalysts were prepared via the co-precipitation method for the catalytic transformation of biomass-derived 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). FDCA acts as a precursor for biodegradable biopolymer polyethylene furanoate production, thereby achieving a carbon-neutral approach. Out of all the synthesized catalysts, CuCo(1:1) showed remarkable catalytic activity and yielded 70.67% FDCA while achieving 100% HMF conversion in 5 minutes at 50 ℃ temperature in the presence of tert-butyl hydroperoxide as an oxidant. Synergistic effects of the catalyst, such as adsorbed oxygen, relative oxygen vacancy, lesser pore size, and pore volume, were key factors attributed to the catalyst's excellent activity. The synthesized catalyst showed good recyclability with a minimal decrease in FDCA yield up to 5 cycles. Pre and post-characterization of catalysts such as BET, TEM, FE-SEM, XRD, H2-TPR, CO2 TPD, ICP-OES, and XPS were done to correlate the catalyst's properties with its activity. In addition, the effect of reaction parameters such as stirring speed, temperature reaction time, catalyst weight, base, and oxidant was studied to achieve optimum reaction conditions. The reaction products were analyzed quantitatively and qualitatively using HPLC and HR-MS.

A GO regulated bimetallic CoFe catalyst for efficient electrochemical nitrate reduction to ammonia under acidic conditions.

Electrocatalytic nitrate reduction to ammonia (ENRA) in acidic media is currently a challenge. Herein, we presented a CoFe2O4/GO catalyst that exhibited a high faradaic efficiency (95.51%) and ammonia yield rate (1268.04 μmol h-1 cm-2) for ENRA under acidic conditions. The ENRA reaction mechanism was investigated through in situ ATR-FTIR spectroscopy and isotope labeling experiments.

Exploring the efficacy of Re-Ni embedded KIT-6/H-Mor catalysts for renewable energy – A comprehensive experimental and theoretical (DFT) exploration

The global market for n-propyl benzene value is projected to reach $30.47 billion by 2030, with a CAGR of 4.3% from 2023 to 2030. This market analysis identifies diverse applications for propyl benzene, spanning the petroleum industry, industrial chemicals, automotive sector, and more. The research introduces eugenol, a compound derived from lignin, as a model compound for bio-oil to n-propyl benzene (bio-fuel analogs) production. A novel Re-Ni/KIT-6-H-Mordenite catalyst is developed for efficient hydrodeoxygenation of eugenol, showcasing high conversion rates and selectivity under moderate temperatures. Comprehensive characterization techniques and theoretical calculations highlight the synergistic interaction between Re and Ni metals. The catalyst’s reusability and successful application for bio-fuel production under atmospheric conditions further validate its potential. This study pioneers the exploration of Re-Ni bimetallic catalysts for HDO of lignin-derived compounds, offering valuable insights into sustainable bio-fuel development.