Bimetallic Nanocatalysts Research Articles

Crystal facet engineering coexposed CuIn (200) and In (101) in CuIn alloy nanocatalysts enabling selective and stable CO2 electroreduction

The electrocatalytic carbon dioxide reduction reaction (eCO2RR) into high-value-added chemicals and fuels is a promising strategy to mitigate global warming. However, it remains a significant stumbling block to the rationally tuning lattice plane of the catalyst with high activity to produce the target product in the eCO2RR process. To attempt to solve this problem, the CuIn bimetallic alloy nanocatalyst with specifically exposed lattice planes is modulated and electrodeposited on the nitrogen-doped porous carbon cloth by a simple two-step electrodeposition method, which induces high Faraday efficiency of 80% towards HCOO− (FEHCOO−) with a partial current density of 13.84 mA cm−2 at −1.05 V (vs. RHE). Systematic characterizations and theoretical modeling reveal that the specific coexposed CuIn (200) and In (101) lattice facets selectively adsorbed the key intermediate of OCHO*, reducing the overpotential of HCOOH and boosting the FEHCOO− in a wide potential window (−0.65–−1.25 V). Moreover, a homogeneous distribution of CuIn nanoparticles with an average diameter of merely ∼3.19 nm affords exposure to abundant active sites, meanwhile prohibiting detachment and agglomeration of nanoparticles during eCO2RR for enhanced stability attributing to the self-assembly electrode strategy. This study highlights the synergistic effect between catalytic activity and facet effect, which opens a new route in surface engineering to tune their electrocatalytic performance.

Spatial self-confinement of heterogeneous metallic CoX (X = Cu, Ni, Fe) within laminated porous carbon assemblies to efficiently activate peroxymonosulfate for tetracycline destruction

Sustainable and universal fabrication of carbon-loaded non-precious bimetallic nanocatalysts with tuned catalytic surface sites is crucially important but challengeable toward peroxymonosulfate(PMS)-motivated antibiotic degradation. We propose herein a universal, easily removable and sustainable salt template-mediated spatial self-confinement strategy to fabricate bimetallic nanoparticles deposited onto lamellar porous carbon assemblies for PMS-assisted tetracycline hydrochloride (TCH) destruction. Among CoX@C-600 (X = Cu, Ni, Fe) samples, CoCu@C-600 has the highest catalytic performance with a degradation efficiency of 98.6% and a rate constant of 0.3174 min−1 for TCH degradation via PMS motivation. The synergy between the heterogeneous metallic Co and Cu nanoparticles, unique tertiary pore structure and copious surface-exposed active sites are responsible for the high performance of CoCu@C-600. The magnetically recoverable CoCu@C-600 shows a good separation property and can be reused for five consecutive runs. Experimental and characterization results affirm the radical/non-radical (major active species of SO4•− and 1O2) and direct electron transfer mechanism. The degradation pathways and toxicity evaluation with the CoCu@C-600/PMS system are unveiled. The rational architecture design and catalytic site regulation are inspirable for universal syntheses of efficient catalysts for antibiotic degradation.

A sustainable solution for diclofenac degradation from water by heterojunction bimetallic nanocatalyst

BackgroundDiclofenac (DCF), a recalcitrant pharmaceutical compound, poses severe environmental concerns due to several health hazards. The Fenton, photo-Fenton, and photo-Fenton-like processes are popular advanced oxidation processes for eliminating toxins from water bodies. Due to its high reactivity and surface properties, nanotechnology has opened newer technological advances in the Fenton-like advanced treatment processes. MethodA facile and one-pot synthesis produces the nanocomposite materials. The natural phytochemicals, in situ, produce the nanoparticles of Fe(NPs) and Ag(NPs), and bentonite is supported with these nanoparticles to create an innovative heterojunction nanocatalyst BN@(Fe(NPs)+(AgNPs)). Additionally, the batch investigations utilize these materials in the photo-Fenton-like degradation of diclofenac in aqueous mediums. Significant findingsThe heterojunction nanocatalyst showed synergistic effects in the remediation of DCF. The nanocatalyst is highly efficient in degrading the DCF (2.0 mg L−1) and removes 83 and 70% of DCF within 2 h under UV-A and LED light irradiations, respectively. Interestingly, the degradation process mineralizes DCF to 74% under UV-A irradiation. Moreover, degrading DCF in a heterogeneous light-assisted Fenton-like process was favorably influenced by increased Fe(II) concentration in the bulk solution. The BN@(Fe(NPs)+Ag(NPs)) nanocatalyst possessed reasonably high stability and reusability for practical applications. Further, the nanocatalyst showed relatively high selectivity in the degradation of DCF using two different natural water samples.

Cobalt Nickel Bimetallic Nanocatalyst Supported on g‐C3N4 for Selective Hydrogenation of α,β‐Unsaturated Carbonyls and Nitroarenes

AbstractDesigned CoNi bimetallic catalysts on various supports were synthesized and tested for selective hydrogenation reactions. Amongst these, the newly developed CoNi@gC3N4 nanocatalyst demonstrated a unique reactivity profile. It was found to be most effective for selective hydrogenation of various chalcone derivatives and nitroarenes in the presence of other reducible functional groups such as halo, carbonyl, benzyl ether, cyclopropane, and isolated alkenes. The prepared bimetallic catalyst has advantages over the reported methods in terms of catalytic activity under mild conditions, selectivity, and reusability. The catalyst CoNi@gC3N4 has ability to selectively reduce nitro functional group to amine and allows formation of quinolines.

Phase Segregation in PdCu Alloy Nanoparticles During CO Oxidation Reaction at Atmospheric Pressure.

Bimetallic nanoparticle (NP) catalysts are widely used in many heterogeneous gas-based reactions because they often outperform their monometallic counterparts. During these reactions, NPs often undergo structural changes, which impact their catalytic activity. Despite the important role of the structure in the catalytic activity, many aspects of how a reactive gaseous environment affects the structure of bimetallic nanocatalysts are still lacking. Here, using gas-cell transmission electron microscopy (TEM), it is shown that during a CO oxidation reaction over PdCu alloy NPs, the selective oxidation of Cu causes the segregation of Cu and transforms the NPs into Pd-CuO NPs. The segregated NPs are very stable and have high activity for the conversion of CO into CO2 . Based on the observations, the segregation of Cu from Cu-based alloys during a redox reaction is likely to be general and may have a positive impact on the catalytic activity. Hence, it is believed that similar insights based on direct observation of the reactions under relevant reactive conditions are critical both for understanding and designing high-performance catalysts.

Co-Promoted CoNi Bimetallic Nanocatalyst for the Highly Efficient Catalytic Hydrogenation of Olefins

Bimetallic catalysts, especially non-noble metals, hold great potential for substituting for noble metals in catalytic hydrogenation. In present study, a series of CoxNiy (x + y = 6) bimetallic catalysts were prepared through the impregnation–reduction method and cyclohexene was chosen as probe-molecule to study the promotion effect of Co on the catalytic olefin hydrogenation reactions. Meanwhile, density functional theory (DFT) was utilized to investigate the formation energies and the charge distribution of CoNi bimetals, as well as the transition state (TS) searches for hydrogen dissociation and migration. The results suggest that bimetals tend to have superior catalytic performance than pure metals, and Co3Ni3 shows the highest catalytic activity on the cyclohexene hydrogenation. It was found that the charge transfer from Co to Ni and the alloying give rise to the refinement of CoNi grains and the improvement of its catalytic activity and stability. Thus, it may be possible to obtain better catalytic performance by tuning the metal/metal atomic ratio of bimetals.

Boosting the Photocatalysis of Plasmonic Au-Cu Nanocatalyst by AuCu-TiO2 Interface Derived from O2 Plasma Treatment.

Plasmonic gold (Au) and Au-based nanocatalysts have received significant attention over the past few decades due to their unique visible light (VL) photocatalytic features for a wide variety of chemical reactions in the fields of environmental protection. However, improving their VL photocatalytic activity via a rational design is prevalently regarded as a grand challenge. Herein we boosted the VL photocatalysis of the TiO2-supported Au-Cu nanocatalyst by applying O2 plasma to treat this bimetallic plasmonic nanocatalyst. We found that O2 plasma treatment led to a strong interaction between the Au and Cu species compared with conventional calcination treatment. This interaction controlled the size of plasmonic metallic nanoparticles and also contributed to the construction of AuCu-TiO2 interfacial sites by forming AuCu alloy nanoparticles, which, thus, enabled the plasmonic Au-Cu nanocatalyst to reduce the Schottky barrier height and create numbers of highly active interfacial sites. The catalyst's characterizations and density functional theory (DFT) calculations demonstrated that boosted VL photocatalytic activity over O2 plasma treated Au-Cu/TiO2 nanocatalyst arose from the favorable transfer of hot electrons and a low barrier for the reaction between CO and O with the construction of large numbers of AuCu-TiO2 interfacial sites. This work provides an efficient approach for the rational design and development of highly active plasmonic Au and Au-based nanocatalysts and deepens our understanding of their role in VL photocatalytic reactions.

Iron-palladium supported graphene as an efficient bimetallic catalyst for the selective oxidation of benzyl alcohol to benzaldehyde

The catalytic oxidation of benzyl alcohol (OBA) is one of the significant methods to produce benzaldehyde, an essential reagent in the chemical and pharmaceutical industries. However, developing an active and efficient catalyst for OBA is a tremendous challenge in commercialization. This research describes a simple, eco-friendly method for producing Fe, Pd, and Fe: Pd bimetallic nanoparticles fabricated by sol immobilization over graphene to conduct OBA. The resulting composite nano-alloys were then characterized using X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The oxidation state and elemental composition of as-fabricated nanoparticles were analyzed using XPS. The point of zero charges (pHPZC) was analyzed and the PZC value indicated that the proposed adsorbent material tends to have a positive charge. The OBA reaction efficiency (87%) of bimetallic nanocatalysts stabilized in graphene support was increased through surface modification of the ratio of both metals. The experimental error was based on three parallel tests and the carbon balance (99.6%) was analyzed during the experiments A proposed reaction mechanism of OBA validated the β-hydride step's elimination by molecular oxygen converting the metal hydride into a water molecule, forming a peroxide intermediate to form water and oxygen molecules. The Fe on the nanocatalyst’s surface is preferentially responsible for the adsorption of the substrate molecule, resulting in the formation of metal-alkoxide. Since it lacks electrons, Fe is more likely to be oxidized, allowing it to perform better than monometallic catalysts in terms of catalytic activity. The present study has great potential to be applied on an industrial scale and studied for industrialists, researchers, and academicians.

Sub-Millisecond Laser-Irradiation-Mediated Surface Restructure Boosts the CO Production Yield of Cobalt Oxide Supported Pd Nanoparticles.

The catalytic conversion of CO2 into valuable commodities has the potential to balance ongoing energy and environmental issues. To this end, the reverse water-gas shift (RWGS) reaction is a key process that converts CO2 into CO for various industrial processes. However, the competitive CO2 methanation reaction severely limits the CO production yield; therefore, a highly CO-selective catalyst is needed. To address this issue, we have developed a bimetallic nanocatalyst comprising Pd nanoparticles on the cobalt oxide support (denoted as CoPd) via a wet chemical reduction method. Furthermore, the as-prepared CoPd nanocatalyst was exposed to sub-millisecond laser irradiation with per-pulse energies of 1 mJ (denoted as CoPd-1) and 10 mJ (denoted as CoPd-10) for a fixed duration of 10 s to optimize the catalytic activity and selectivity. For the optimum case, the CoPd-10 nanocatalyst exhibited the highest CO production yield of ∼1667 μmol g-1catalyst, with a CO selectivity of ∼88% at a temperature of 573 K, which is a 41% improvement over pristine CoPd (~976 μmol g-1catalyst). The in-depth analysis of structural characterizations along with gas chromatography (GC) and electrochemical analysis suggested that such a high catalytic activity and selectivity of the CoPd-10 nanocatalyst originated from the sub-millisecond laser-irradiation-assisted facile surface restructure of cobalt oxide supported Pd nanoparticles, where atomic CoOx species were observed in the defect sites of the Pd nanoparticles. Such an atomic manipulation led to the formation of heteroatomic reaction sites, where atomic CoOx species and adjacent Pd domains, respectively, promoted the CO2 activation and H2 splitting steps. In addition, the cobalt oxide support helped to donate electrons to Pd, thereby enhancing its ability of H2 splitting. These results provide a strong foundation to use sub-millisecond laser irradiation for catalytic applications.

Selective aerobic oxidation of benzyl alcohol under ambient conditions using polyionic nanoclay-supported gold/palladium nanoparticles

Oxidation of alcohols to their respective aldehydes, esters, and acids is a common value-added industrial process, though techniques often rely on harsh reaction conditions (e.g., high temperature, strong base, organic solvents, hydrothermal processes) to achieve rapid reaction turnovers. The incorporation of gold and palladium nanoparticles facilitates the dehydrogenation and O2 reduction processes, respectively, and these advantages can be dually incorporated and enhanced using supported nanoparticle alloys. Herein, we utilize polyionic nanoclays (PINCs) as two-dimensional inorganic-organic architectures for supporting monometallic and bimetallic gold and palladium nanocatalysts for the model oxidation of benzyl alcohol to the corresponding aldehyde, ester, and acid. In addition, we present two new PINC surface chemistries (N-methylpyrrolidinium- and pyridinium-functionalized PINCs) and compare their performances as catalyst supports to show that catalyst enhancement is altered by the PINC surface chemistry. Reaction conditions are mild (aqueous, room temperature, open to atmosphere, weak or no base) yet reaction turnovers are comparable to those of more demanding literature accounts.

Ni-Cu bimetallic catalytic membranes for continuous nitrophenol conversion

Bimetallic nanocatalysts are of great interest due to their greater activity, selectivity, and chemical and electrochemical stability, compared to their monometallic counterparts. Bimetallic nanocatalysts formed from abundant and inexpensive elements provide greater opportunities for applications over noble metal catalysts. In this study, inexpensive Ni-Cu bimetallic catalytic membrane microreactors (CMMRs) were synthesized in a simple two-step process to catalytically degrade the environmental pollutant, 4-nitrophenol (4-NP), and produce the valuable feedstock, 4-aminophenol (4-AP). Ni-Cu nanoparticles were either produced by a replacement reduction reaction or a co-reduction reaction, producing either bimodal or integrated nanostructures, respectively, as demonstrated by transmission electron microscopy (TEM), while the electronic reconfiguration between bimetallic systems was verified by X-ray photoelectron spectroscopy (XPS). Compared to 4-NP batch conversion, flow-through reactions demonstrated enhanced mass transfer contributing to 2-fold higher conversion (>99%), 30-fold higher processing capacity (0.95 mol∙m−2∙h−1) and co-reduced Ni-Cu CMMRs boasted a reaction rate constant of 725.03 min−1.4-NP conversion on the Ni-Cu catalysts in the presence of NaBH4 followed the Langmuir-Hinshelwood (L-H) mechanism, and the conversion efficiency was highly dependent on flow rate, representing an optimization trade-off critical for CMMR applications. The polydopamine-assisted fabrication and the tortuous membrane pore structure contributed to the CMMRs’ stability with <5% metal loss during operation. The enhanced activity was attributed to the synergistic electronic effects of the Ni-Cu bimetallic structure, the metal-polydopamine interactions, and the catalysts’ unique structure and high surface area.

Enhanced catalytic performance of Pd-Pt bimetallic alloy nanocatalyst for hydrogenation of nitrile butadiene rubber

Nowadays, the rational design of high-performance catalysts with desirable resistance to metal leaching has become the principal challenge in the hydrogenation of nitrile butadiene rubber. In the present work, the Pd-Pt bimetallic alloy nanocatalyst exhibits an outstanding hydrogenation degree of 99.0%, obviously higher than that of the conventional monometallic Pd/SiO2 catalyst with the same Pd content (92.9%), accompanied by approximately 100% selectivity to C=C bonds. The results reveal that electron transfer from Pt to Pd confirms that the Pd species are in a rich-electron state, which boosts hydrogen activation and improves catalytic activity. Additionally, the incorporation of inactive Pt species promotes the formation of uniformly dispersed Pd-Pt alloy nanoparticles. The incorporation of inactive Pt species can enhance the metal-support interaction, reducing the residual metal content in hydrogenated nitrile butadiene rubber. The current research demonstrates a simple procedure for designing efficient bimetallic catalysts for the hydrogenation of unsaturated elastomer.

Highly selective PtCo bimetallic nanoparticles on silica for continuous production of hydrogen from aqueous phase reforming of xylose

Hydrogen (H2) is a promising energy vector for mitigating greenhouse gas emissions. Lignocellulosic biomass waste has been introduced as one of the abundant and carbon-neutral H2 sources. Among those, xylose with its short carbon chain has emerged attractive, where H2 can be catalytically released in an aqueous reactor. In this study, a composite catalyst system consisting of silica (SiO2)-supported platinum (Pt)-cobalt (Co) bimetallic nanoparticles was developed for aqueous phase reforming of xylose conducted at 225 °C and 29.3 bar. The PtCo/SiO2 catalyst showed a significantly higher H2 production rate and selectivity than that of Pt/SiO2, whereas Co/SiO2 shows no activity in H2 production. The highest selectivity for useful liquid byproducts was obtained with PtCo/SiO2. Moreover, CO2 emissions throughout the reaction were reduced compared to those of monometallic Pt/SiO2. The PtCo bimetallic nanocatalyst offers an inexpensive, sustainable, and durable solution with high chemical selectivity for scalable reforming of hard-to-ferment pentose sugars.

Preparation of graphene supported Ni–Fe bimetallic nanocatalyst and its catalytic upgrading and viscosity reduction performance for heavy oil

Graphene supported single metal catalyst can improve the dispersion of active components and enhance the viscosity reduction effect of heavy oil. However, there is little research on graphene-supported bimetallic catalysts in the field of heavy oil upgrading and viscosity reduction. In this paper, super heavy oil of Liaohe Oilfield was taken as the research object. Graphene was selected as the carrier material, and nickel and iron chlorides were used as precursors. Graphene-supported nickel-iron bimetallic nanocatalysts were prepared by solvothermal method, and their synthesis feasibility was proved by microscopic characterization. Then the prepared catalyst was used in the evaluation experiment of catalytic upgrading and viscosity reduction performance of Liaohe heavy oil. By analyzing the parameters of oil samples before and after catalytic upgrading and viscosity reduction, the catalytic upgrading and viscosity reduction effect was evaluated and the viscosity reduction mechanism was revealed. The results showed that the viscosity reduction rate of heavy oil with graphene supported Ni–Fe bimetallic catalyst was 42.38%. With the aid of decalin, the viscosity reduction rate of heavy oil could reach 71.43%. At this time, the content of heavy components, the average molecular weight of heavy components and the aromaticity fA of oil samples decreased after catalytic upgrading and viscosity reduction, while the aromatic condensation degree HAU/CA and the branched chain index BI increased, and the modification effect was significant. Among them, the average molecular weight of asphaltene decreased from 2266 to 1444, with the most obvious decrease. The decrease of heteroatom content in asphaltene led to a significant decrease in intermolecular force and hydrogen bonding, which was the main reason for the catalytic upgrading and viscosity reduction of heavy oil by graphene supported Ni–Fe bimetallic catalyst.

Non-Noble FeCrOx Bimetallic Nanoparticles for Efficient NH3 Decomposition

Ammonia has the advantages of being easy to liquefy, easy to store, and having a high hydrogen content of 17.3 wt%, which can be produced without COx through an ammonia decomposition using an appropriate catalyst. In this paper, a series of FeCr bimetallic oxide nanocatalysts with a uniform morphology and regulated composition were synthesized by the urea two-step hydrolysis method, which exhibited the high-performance decomposition of ammonia. The effects of different FeCr metal ratios on the catalyst particle size, morphology, and crystal phase were investigated. The Fe0.75Cr0.25 sample exhibited the highest catalytic activity, with an ammonia conversion of nearly 100% at 650 °C. The dual metal catalysts clearly outperformed the single metal samples in terms of their catalytic performance. Besides XRD, XPS, and SEM being used as the means of the conventional characterization, the local structural changes of the FeCr metal oxide catalysts in the catalytic ammonia decomposition were investigated by XAFS. It was determined that the Fe metal and FeNx of the bcc structure were the active species of the ammonia-decomposing catalyst. The addition of Cr successfully prevented the Fe from sintering at high temperatures, which is more favorable for the formation of stable metal nitrides, promoting the continuous decomposition of ammonia and improving the decomposition activity of the ammonia. This work reveals the internal relationship between the phase and structural changes and their catalytic activity, identifies the active catalytic phase, thus guiding the design and synthesis of catalysts for ammonia decomposition, and excavates the application value of transition-metal-based nanocomposites in industrial catalysis.

Theoretical and Experimental Study for Cross-Coupling Aldol Condensation over Mono- and Bimetallic UiO-66 Nanocatalysts

Mono- and bimetallic UiO-66 nanocatalysts were synthesized using the solvothermal synthesis method and evaluated in the aldol condensation reaction of benzaldehyde and acetone in a batch reactor. N2 physisorption, thermogravimetric analysis, temperature-programmed desorption of ammonia, X-ray diffraction, field-emission scanning electron microscopy–energy-dispersive X-ray, X-ray photoelectron spectroscopy, potentiometric titration, and Fourier transform infrared were used to characterize the nanocatalysts. The higher activity exhibited by the Zr/Hf-UiO-66 catalyst could be attributed to the lower orbital energy interaction with benzaldehyde, as shown by density functional theory. A synergetic effect is observed for the bimetallic UiO-66 nanocatalyst between Zr and Hf, obtaining a higher reaction rate than the monometallic nanocatalysts. Meanwhile, this antagonistic effect was shown in the bimetallic catalysts between Zr and Ce, which was less active than the monometallic UiO-66 catalyst due to free COOH generated during the synthesis. Finally, the selectivity results showed that incorporating Hf and Ce on Zr-UiO-66 favors benzalacetone formation by cross-coupling condensation of benzaldehyde and acetone at isoconversion conditions.

Catalytic boosting on AuCu bimetallic nanoparticles by oxygen-induced atomic restructuring

Understanding the structure-activity relationship over silica-supported Au-based bimetallic nanocatalysts in CO oxidation is essential in elucidating active sites and catalytic mechanisms. Here, we uncover that structure-activity relationship over a silica-supported 10 nm sized AuCu bimetallic model nanocatalyst for CO oxidation. Oxygen–induced atomic restructuring of AuCu nanocrystals is comprehensively investigated using combined operando spectroscopic and microscopic techniques, including near-ambient-pressure X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier-transform spectroscopy, and environmental transmission electron microscopy. We show that the formation of CuOx/Au heterostructure gives rise to the enhancement of catalytic activity for CO oxidation. The formation of the reactive heterostructure on catalysis was rationalized by density functional theory calculation. Our results indicate that intermediate heterostructure with a metal-oxide interface leads to strong electronic coupling between catalyst and support (i.e., electronic metal-support interaction effect).

Synthesis of Mesoporous Silica-Supported NiCo Bimetallic Nanocatalysts and Their Enhanced Catalytic Hydrogenation Performance.

In this work, mesoporous silica SBA-16-supported NiCo bimetallic nanocatalysts were synthesized by coimpregnation of Ni and Co precursors followed by calcination and reduction, and various characterization techniques confirm the formation of NiCo bimetallic nanostructures in the catalysts. The synthesized NiCo/SBA-16 shows enhanced catalytic performance for hydrogenation of a series of nitroaromatics. Under the reaction conditions of 80 °C and 1.0 MPa of H2, the yields of aniline for nitrobenzene hydrogenation over NiCo0.3/SBA-16 can reach more than 99% at 2.0 h. The enhanced catalytic performance can be ascribed to the formation of NiCo bimetallic nanostructures, where the synergistic effect between Ni and Co improves their catalytic activities for hydrogenation of nitroaromatics.

Preparation and characterization of bimetallic zero-valent iron nanocatalysts for nitrophenol degradation

Backgroundp-Nitrophenol (4-NP) is an organic pollutant found in wastewater discharged from agricultural facilities worldwide. This pollutant is considered as hazardous and toxic by the US Environmental Protection Agency (USEPA). MethodsThe spherical chain-shaped nanophase zero-valent-iron (nZVI) with different metal (Ag, Cr, Cu) loadings was used for wastewater simulation to form bimetallic nanocatalyst (BNC). Moreover, the nZVI and BNC was synthesized and characterized for 4-NP removal. The as-synthesized nZVI and BNCs were used to degrade 4-NP in wastewater, where a higher conversion of 4-NP to aminophenol (4-AP) was observed. The core-shell shape of nZVI@Cu BNCs was also investigated with small angle X-ray scattering (SAXS) to demonstrate the parameters of core-shell model in SAS View. Significant findingsExperimentally, the Cu removal efficiencies at different loading ratios were nZVI@Cu-800> nZVI@Cu-400> nZVI@Cu-200> nZVI@Cu-100. The thermal induced aggregations of nZVI were demonstrated with SAXS, where the 55 °C group displayed 181% increase in size when compared with the 25 °C group. The XANES/EXAFS spectra revealed the presence of Cu2O in nZVI@Cu, a phenomenon which provided the reductive degradation mechanism of the chemical reactions. In this study, heavy metal absorbed onto nZVI and BNCs reduced 4-NP heavy metal contaminants to less toxic 4-AP. Thus, the as-synthesized nZVIs could effectively convert harmful 4-NP in wastewater into useful and high-value 4-AP by-products.

The exceptional performance of the plasmonic Au-Fe/TiO2 nanocatalysts achieved by O2 plasma activation

The plasmonic Au-based bimetallic nanocatalysts have the potential to exhibit superior visible-light (VL) photocatalytic activity, and their performance in reaction is greatly dependent on the method of activation. Herein, Au-Fe/TiO2 nanocatalysts are prepared by a modified incipient wetness impregnation method with the precursors of HAuCl4 and FeCl3. The visible-light activities of the samples activated by calcination at 300 °C, 50%H2/Ar plasma and O2 plasma are compared using CO oxidation. Au-Fe/TiO2 activated by O2 plasma has the most exceptional performance with a CO conversion of 90%. The samples are characterized by transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, and CO chemisorption. It is found that O2 plasma restructures nano Au and Fe on the TiO2 support into Au-Fe alloy, preventing nano Au particle size increase. The Au-Fe alloy nanoparticles on TiO2 has a narrow size distribution and are approximately 4 nm in size. Many surface oxygen species on Au-Fe alloy are observed, as well as a unique board peak assigned to CO adsorption, and they can improve the activity and stability of Au-Fe alloy in CO oxidation. Finally, a reaction mechanism of Au-Fe/TiO2 activated by O2 plasma for CO oxidation is developed. This research demonstrates that the treatment of O2 plasma is an available approach to producing efficient Au-Fe plasmonic nanocatalysts.