Binary Catalysts Research Articles

Carbon dots anchored NiAl-LDH@In2O3 hierarchical nanotubes for promoting selective CO2 photoreduction into CH4

The efficient conversion of CO2 into hydrocarbon fuels (CH4) with high selectivity is considered as a great challenge in photocatalysis owing to the multiple-electron transfer pathway and competitive H2 generation. Herein, we developed carbon dots (CDs)-modulated S-scheme heterojunction of CDs/NiAl-LDH@In2O3 (C-DH@IN) through a facile in-situ hydrothermal method. Thanks to the multi-shell nanotube structure, the C-DH@IN shows an enhanced CH4 evolution rate of 10.67 µmol h−1 g−1 and higher selectivity of CH4 (85.70%) compared with In2O3 and NiAl-LDH@In2O3 binary catalyst in the pure water without sacrificial agent. Electron spin resonance (ESR) and in situ Fourier transform infrared spectra verify that the constructed S-scheme heterojunction can possess the strong redox capability and the HCOO− and CH3O− as critical intermediates play an important role in selective CO2 reduction to generate CH4. Furthermore, CDs with superior photoabsorption can boost the electron transfer and absorb H+, thus improving the integration of H+ and CO2 molecule. Therefore, this work emphasizes a facile strategy to achieve efficient CO2-to-CH4 conversion based on construction of CDs-based heterojunction catalysts.

Reversible trans-alkylation mechanisms at homogeneous catalytic systems investigated by a combined DFT and ASM-NEDA approach

We studied the reversible trans-alkylation(s) mechanism for the chain shuttling process by means of density functional theory (DFT) calculations combined with%VBur steric maps and the Activation Strain Model (ASM) coupled with Natural Energy Decomposition Analysis (NEDA). Our results revealed that the two partners of the catalytic pair involved in the industrial process for olefin-based block copolymers formation show comparable coordination energies with the chain shuttling agent and this similarity is due to the (fortuitus) ligand modification in situ by one of the two systems. The further extension of our analysis to several ligand classes (from ansa-metallocenes to octahedral nonmetallocenes) rule out the possibility of using binary catalysts with different coordination geometries as suitable pair.

Construction of S-Scheme Co2SnO4/graphdiyne heterojunction to promote carrier transfer for efficiently photocatalytic hydrogen evolution characterized with in situ XPS

Graphdiyne (g-CnH2n-2), a novel two-dimensional carbon isomeric material consisting of a network of sp and sp2 co-hybridized hybridized carbons, has been highly regarded for its excellent chemical and physical properties and unique structure since it was first synthesized in 2010. However, as a photocatalyst, its application in the field of hydrogen production is still rare, which is a good opportunity for the field of photochemical catalyze hydrogen production. In this work, a binary catalyst Co2SnO4/graphdiyne was constructed by calcining graphdiyne and CoSn(OH)6 together after grinding. The structure of high-temperature calcination closely linked Co2SnO4 and graphdiyne, which led to an increased contact area and more active sites with faster photogenerated electron transfer efficiency. Therefore, Co2SnO4/graphdiyne showed good photocatalytic hydrogen production efficiency. Under the optimum amount of EY the hydrogen production rate reached 8.79 mmol g−1 h−1, which was 80.11 and 33.70 times higher than that of Co2SnO4 and graphdiyne, respectively. The construction of Co2SnO4/graphdiyne S-scheme heterojunction proved by in-situ XPS, EPR (DMPO-•O2−) experiment and the hydroxyl radical detection experiment retains high redox potential and prolongs the lifetime of photo-generated carriers. The catalyst preparation method in this work is innovative, which provides a general and high-efficiency strategy for applying the graphdiyne-based S-scheme heterojunction photocatalyst to solar energy-hydrogen energy conversion for photocatalytic water decomposition into hydrogen.

An efficient NiFe binary alloy anode catalyst for direct borohydride fuel cells

The NiFe-x binary alloy catalysts have been prepared by one-step potentiostatic electrodeposition, while the effects of the introduction of Fe on the morphology, structure, and electrochemical properties have been also investigated sufficiently. The research results indicate that because of the introduction appropriate amount of Fe, the size of the catalyst particles is refined, which is beneficial to increase effective catalytic active sites and enhancement catalytic activity. At the same time, it changes the electron distribution of Ni thereby improving the adsorption to reactants. Moreover, it can also inhibit hydrogen evolution reaction (HER) thus to heighten the catalytic selectivity. When assembled with the NiFe-2 catalyst anode, the direct borohydride fuel cell (DBFC) can provide a peak power density of 540 mW cm−2 and the open circuit voltage (OCV) of 1.87 V at 298 K. We believe that this study may enlighten a new idea for the design and development of efficient noble metal-free anode catalysts of DBFC.

Enriched electrophilic oxygen species facilitate acidic oxygen evolution on Ru-Mo binary oxide catalysts

Enriched electrophilic oxygen species facilitate acidic oxygen evolution on Ru-Mo binary oxide catalysts

Determination of Optimum pH and NH3 Concentration of Malachite Ore for NH3/NH4NO3 Leaching by Response Surface Method to Produce Cu/Zn Oxide Binary Catalyst

Bu çalışmada, bir hidrosikarbonat minerali olan malahit ve bir karbonatlı mineral olan simitsonit içeren bakır cevherinin hidrometalurjik yöntemle işlenmesi neticesinde Cu/Zn oksit ikili katalizörü üretilmiştir. Cevherden maksimum oranda bakır ve minimum oranda çinkonun liç çözeltisine geçmesini sağlayacak ancak cevherde bulunan diğer metallerin çözünmesini engelleyecek pH ve çözücü derişiminin optimum değerleri yanıt yüzey yöntemi ile belirlenmiştir. Yanıt yüzey yönteminde elde edilen deneysel bulgulara çoklu regresyon analizi yapılarak bakır ve çinko liç verimleri ile bağımsız değişkenler arasındaki ilişkiyi gösteren ikinci dereceden model denklemler elde edilmiştir. Bakır ve çinko liç verimi üzerine NH3 derişiminin pH’dan daha etkili bir parametre olduğu belirlenmiştir. NH3 ve NH4NO3 derişimleri ile pH için optimum değerler sırasıyla 0,38 M, 0,11 M ve 9,80 olarak bulunmuştur. Optimum koşullarda cevherdeki bakırın %82,3’ünün çinkonun ise %45,1’inin çözeltiye geçtiği belirlenmiştir. Liç sonucunda elde edilen çözeltideki Cu+2 ve Zn+2 iyonları Na2CO3 çözeltisi ile çöktürülmüş ve oluşan katı ürün 350 °C’de 6 saat süreyle kalsine edilerek Cu/Zn oksit ikili katalizörü üretilmiştir. Katalizörün ağırlıkça bakır oksit içeriği yaklaşık %44 ve çinko oksit içeriği %56 olarak tespit edilmiştir.

A principal component analysis assisted machine learning modeling and validation of methanol formation over Cu-based catalysts in direct CO2 hydrogenation

With the advent of powerful machine learning algorithms strongly supporting complex non-linear regression modeling, catalyst design features for a wide and customized set of catalysts used for a specific reaction have been made easy. Herein, we use these techniques in the methanol synthesis by CO2 reduction over Cu-based binary and ternary catalysts with the help of three machine learning algorithms: artificial neural network, support vector machine regression, and gaussian process regression. 227 catalytic performance dataset points from existing literature on CO2 hydrogenation to methanol were compiled and initially accessed by Principal Component Analysis (PCA) for training and preliminary evaluation of the algorithms, which was further guided using a 10-fold cross-validation method. The predictive model and its insights were validated experimentally over 30 datasets derived from experimental runs of this reaction over a ternary Cu/ZnO/ZrO2 laboratory-synthesized catalyst at varying conditions of temperature, pressure, and space velocity in a continuous mode fixed-bed plug-flow reactor. The assessment of the space of input and laboratory data was aided by Principal Component Analysis (PCA), scores, and loadings plot. This work shows how experimentalists can predict typical heterogeneous catalytic reaction outputs (R2 greater than 0.9 for three variables) with fair accuracy using a combination of machine learning and PCA.

Revealing the effect of electronic interaction between dual redox sites on CeO2-Fe2O3 NH3-SCR catalyst through interface contact tailoring

Due to the requirements of different applications environments, higher catalytic activity or SO2 and H2O tolerance, the binary or ternary metal oxide NH3-SCR catalysts with dual redox sites have been widely studied in recent years. The electronic interaction between the dual redox sites has a significant impact on the catalyst performance. Herein, a series of CeO2-Fe2O3 composite catalysts with continuously enhanced interface contact as well as electronic interactions were prepared through a facile grinding method. The activity tests showed that neither the catalyst with the least interfacial contacts nor the one with the greatest interfacial contacts exhibited the highest NOx removal activity. The comprehensive characterizations demonstrated that the apparent physicochemical properties including the NH3 adsorption ability, redox property, and so on, changed in favor of NH3-SCR reaction when enhancing the interface contact for the CeO2-Fe2O3 composite catalysts. However, the reaction mechanism as well as the reactivity of main NH3 and NO adsorbed species were also altered by the electronic interactions between Ce and Fe active species. The unsatisfactory NOx removal activity of the CeO2-Fe2O3 catalyst with strongest electronic interactions between Ce and Fe active species was explained by the reactivity of main NH3 and NO adsorbed species. This work can provide new ideas for improving the performance of NH3-SCR catalysts through changing the interface contact and electronic interaction between the dual redox sites.

Optimal Architecture of a Dual S-Scheme ZnIn2S4-ZnO-Al2O3 Heterosystem with High H2 Evolution Rate under Visible Light.

In this study, dual S-scheme ZnIn2S4-Al2O3-ZnO (ZIS-Al-Zn) heterojunctions were produced by a facile, low cost, and rapid combustion technique. These heterojunctions accelerated the photocatalytic hydrogen production due to the multi-channel-promoted separation of photocarriers. By optimizing the content of the components, the synthesized ZIS-Al-Zn composite with 20 wt% of ZnIn2S4 and 30 wt% of Al2O3 in the ZIS-Al-Zn composite demonstrated the highest hydrogen production rate of 54.2 mmol g-1 h-1, which was nearly 11 and 8.30 times better than ZnO-Al2O3 and ZnO-ZnIn2S4 composites, respectively. The results of DRS, PL, EIS, LSV, and CV techniques showed the highest shift in the light absorption, rapid interfacial transfer, and quenched recombination of photocarriers over the ternary ZIS-Al-Zn composite than single and binary catalysts. The obtained results revealed the formation of a dual S-scheme mechanism of transfer of photocarriers in ZIS-Al-Zn heterojunctions, contributing to better hydrogen production efficiency. The optimized ZIS-Al-Zn composite also exhibited good stability and reusability.

Confinement Effects of Hollow Structured Pt-Rh Electrocatalysts toward Complete Ethanol Electrooxidation.

In the anodic ethanol oxidation reaction (EOR) for direct ethanol fuel cells, the coverage of hydroxide (OHads) is a major adsorbent competing with C-C bond cleavage, which is necessary for complete ethanol oxidation (C1-pathway) and durability. Beyond utilizing a less-alkaline electrolyte that causes ohmic losses, an alternative strategy to optimize OHads coverage is to intentionally exploit local pH changes near the electrocatalyst surface that are governed by a combination of released H+ during EOR and OH- mass transport from the bulk solution. Here, we manipulate the local pH swing by fine-tuning the electrode porosity with Pt1-xRhx hollow sphere electrocatalysts based on particle size (250 and 350 nm) and mass loading. With the smaller size of 250 nm, Pt0.5Rh0.5 (∼50 μg cm-2) shows a high activity of 1629 A gPtRh-1 (2488 A gPt-1) in a 0.5 M KOH-containing electrolyte, which is ∼50% higher than the most active binary catalysts to date. Moreover, a higher C1-pathway Faradaic efficiency (FE) of 38.3% and 80% longer durability are achieved with a 2-fold increase in mass loading. In the more porous electrodes, a local acidic environment created by hindered OH- mass transport better optimizes OHads coverage, providing more active sites for the desired C1-pathway and a continuous EOR.

Heterojunction Mo-based binary and ternary nitride catalysts with Pt-like activity for the hydrogen evolution reaction

The development of earth-abundant electrocatalysts with Pt-like catalytic activity for the hydrogen evolution reaction (HER) is of great significance to green hydrogen production. Herein, a novel strategy is described to construct dual-phase nitride nanobelts composed of Mo2N and Ni0.2Mo0.8N by nitridation of Ni2+ intercalated layered MoO3 nanobelts (NBs). The Mo2N/Ni0.2Mo0.8N catalyst exhibits superior stability and a low overpotential of 26 mV at 10 mA cm−2 and Tafel slope of 31 mV dec−1 in both the alkaline electrolyte and simulated seawater, which is comparable to or better than that of the benchmark Pt/C catalyst. The excellent alkaline HER characteristics is attributed to the Mo2N/Ni0.2Mo0.8N heterostructure with adjustable content and robust interfaces and without metal Ni segregation and structure collapse during nitridation. Density-functional theory (DFT) calculations and experiments reveal that the Mo2N/Ni0.2Mo0.8N interface with strong electronic interactions optimizes H adsorption/desorption yielding moderately weak bonding metal sites with positive ΔGH* as the catalytic centers, thereby accelerating the HER kinetics and boosting the HER activity. The results reveal a simple strategy for the preparation of heterostructured nitride-based catalysts with Pt-like activity for hydrogen evolution.

CdS Covered with Ga-P Electron Exchange Membrane for Efficient Photocatalytic Hydrogen Prodection

Abstract: CdS is one of the best semiconductor photocatalysts. However, photocorrosion will occur when CdS takes part in the photocatalytic system. The general solution is to add sacrificial reagents to inhibit this phenomenon. Even so, it can not maintain the stability of CdS. In order to improve the stability and efficiency of CdS in pure water, Ga-P electron exchange membrane was designed to modify its surface. Under radiation of visible light, a significant increase can be observed in hydrogen production activity. In the absence of Pt as electron transfer agent, the modification of Ga-P realizes decomposition of pure water from zero to one. At the same time, the hydrogen production rate is increased about 5 times with Pt and catalytic life is greatly extended. Through proof of controlled experiment, Ga-P electron exchange membrane can not only prolong the lifetime of photogenerated electrons, but also change the direction of electrons. The formation of a protective membrane makes composite photocatalyst improve the stability and enhance the photocatalytic activity. Based on the analysis of TEM, fluorescence lifetime, UV-Vis diffuse reflection and photocurrent response, the mechanism is analyzed from atomic radius, nuclear orbit and energy level. For homogeneous electronic band structure and XPS analysis, we determined that the binary catalyst formed an S-scheme heterojunction. The work provides a potential way to design a more efficient and stable composite photocatalyst in the future. And contributed to the development of S-scheme heterojunctions.

Understanding the Bifunctional Trends of Fe-Based Binary Single-Atom Catalysts.

Binary single-atom catalysts (BSACs) have demonstrated fascinating activities compared to single atom catalysts (SACs) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Notably, Fe SACs is one of the most promising ORR electrocatalysts, and further revealing the synergistic effects between Fe and other 3d transition metals (M) for FeM BSACs are very important to enhance bifunctional performance. Herein, density functional theory (DFT) calculations are first adapted to demonstrate the role of various transition metals on the bifunctional activity of Fe sites, and a notable volcano relationship is established through the generally accepted adsorption free energy that ΔG* OH for ORR, and ΔG* O -ΔG* OH for OER, respectively. Further, ten of the atomically dispersed FeM anchored on nitrogen-carbon support (FeM-NC) are successfully synthesized with typical atomic dispersion by a facile movable type printing method. The experimental data confirms the bifunctional activity diversity of FeM-NC between the early- and late- transition metals, agrees very well with the DFT results. More importantly, the optimal FeCu-NC shows the expected performance with high ORR and OER activity, thereby, the assembled rechargeable zinc-air battery delivers a high power density of 231mW cm-2 , and an impressive stability that can be stably operated over 300h.

La–Ce binary oxide catalysts for low-temperature dry reforming

A series of Ni-based catalysts supported by La–Ce binary oxide were synthesized by a one-pot microwave-assisted hydrothermal method. With fine-tuning of the La/Ce ratio and synthesis process, fabricated Ni/La–Ce catalysts showed comparable catalytic performance in low-temperature dry reforming of methane (DRM). With a La/Ce ratio of 1:4, the synthesized catalyst had optimal conversions of reactants but severe coke formation. When La/Ce ratio increased to 1:1, with declined DRM reactivity Ni/La–Ce catalyst showed great coke resistance. Different characterizations had been performed on the fresh and spent Ni/La–Ce catalyst to evaluate the correlations between structures and surface properties with the catalytic performance of catalysts. It was found that synthesis and carbonate species formed on the surface of La–Ce binary oxide played important roles in the DRM reaction. The La–Ce binary oxide had its intrinsic lattice configuration with La inserting into the CeO2 phases and proved its efficiency in low-temperature DRM reactions.

Carbon-Dots-Modified Hierarchical ZnIn2S4/Ni-Al LDH Heterojunction with Boosted Charge Transfer for Visible-Light-Driven Photocatalytic H2 Evolution.

The construction of a heterojunction structure is considered a significant route to promote solar-driven H2 production. Herein, a CDs/ZnIn2S4/Ni-Al LDHs (CDZNA) ternary heterojunction was elaborately constructed via the in situ growth of ZnIn2S4 on Ni-Al LDHs with the incorporation of carbon dots (CDs) cocatalyst, which was used as a highly efficient catalyst for the photocatalytic H2 generation. Characterizations indicated that 2D ZnIn2S4 nanosheet homogeneously dispersed on the surface of Ni-Al LDHs fabricated an intimate hierarchical architecture and provided a high BET surface area (135.12 m2 g-1). In addition, the unique embeddable-dispersed CDs as electron mediators possessed numerous active sites and promoted the charge separation on ZnIn2S4/Ni-Al LDHs (ZNA) binary catalyst. By coupling these two features, the CDZNA catalyst exhibited a considerable H2 production rate of 23.1 mmol g-1 h-1 under visible-light illumination, which was 16.4 and 1.4 times higher than those of ZnIn2S4 and ZNA, respectively. A proposed mechanism of photocatalytic H2 production over the CDZNA catalyst was also discussed. This work provides a promising strategy to achieve highly efficient solar energy conversion in a ternary photocatalytic system.

Carbon Dioxide Cycloaddition to Epoxides: A Comparative Study on the Catalytic Activities of Two Binary Catalysts VIVO(N2O2)/TBAB and VVO2(O2N)/TBAB and In Situ Derivation of a Bifunctional Catalyst

Carbon Dioxide Cycloaddition to Epoxides: A Comparative Study on the Catalytic Activities of Two Binary Catalysts VIVO(N2O2)/TBAB and VVO2(O2N)/TBAB and In Situ Derivation of a Bifunctional Catalyst

STEAM CONVERSION OF ETHANOL TO HYDROGEN OVER CO-CE-O CATALYSTS

In the offered article, the reaction of steam conversion of ethanol to hydrogen over binary cobalt-chromium oxide catalysts was explored. It had been found that at temperatures up to 400°C, ethanol is mainly converted into ethyl acetate. It is shown that with increasing reaction temperature, the yield of ethyl acetate passes through a maximum. At the high temperatures of the ethanol steam reforming reaction, the main reaction product is hydrogen. The peak yield of hydrogen is detected over the catalyst Co: Ce=1:9 at 650°C and is equal to 89.9%. It has been demonstrated that carbon monoxide and methane are by-products of the reaction of the steam conversion of ethanol into hydrogen. Keywords: Ethanol conversion, binary catalysts, cerium oxide, hydrogen, ethyl acetate.

Catalytic Hydrogenation of Anthracene on Binary (Bimetallic) Composite Catalysts

The catalytic activity of the binary composite catalysts of Fe2O3-CoO/CaA and Fe2O3-CoO/ZSM-5 was studied. They were obtained by impregnation of CaA and ZSM-5 zeolites with aqueous solutions of sulfates of iron (FeSO4·7H2O) and cobalt (CoSO4·7H2O). The total metal content was no more than 5%. Then, oxidizing burning at 720 °C for 60 min was performed to produce the metal oxides. It was found that the obtained Fe-Co/CaA catalyst contains iron and cobalt as CoFe2O4 compound, and the Fe-Co/ZSM-5 catalyst includes CoFe2O4 and CoFe. The phase composition of the obtained catalysts was detected by the X-ray diffraction analysis. The surface morphology was investigated by the electron microscopy. The elemental composition of the obtained catalysts was determined by energy dispersive spectroscopy with mapping and inductively coupled plasma atomic emission spectroscopy. The atomic absorption analysis by the IR-spectroscopy showed the shifts of absorption bands in the infrared spectra of the pure zeolites and with added Fe and Co. The catalytic hydrogenation of anthracene was performed to determine the catalytic properties of the obtained catalysts. It is one of the most common model compounds applied to investigate the efficiency of catalytic systems. The result of hydrogenation found that conversion of anthracene at 400 °C, initial pressure of 6 MPa and duration of 60 min using the Fe-Co/CaA catalytic system equaled to ~87%. However, hydrogenation products equaled to ~84%. Anthracene conversion using the Fe-Co/ZSM-5 catalytic system and the same conditions was ~91%; among them, hydrogenated derivatives were ~71%. The proposed method is characterized by its simple execution. The obtained catalysts are be slightly inferior to platinum and rhodium catalysts in the catalytic activity.

Ternary single atom catalysts for effective oxygen reduction and evolution reactions

Synergistic effects have been demonstrated for binary single-atom catalysts (SACs), while it is still challenging to investigate the activity and performance of ternary SACs due to the lack of robust method to synthesize these materials. Herein, we provide a general approach for the preparation of ternary SACs, and the features of single atoms highly dispersed on the support have been identified and verified. As an illustration, trace platinum decorated iron-cobalt ternary single atom catalysts (PtFeCo/NC) possess an obviously enhanced bifunctional activity of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as high stability. The density functional theory calculations reveal that the synergistic effects induced by the introduction of Pt enable modulating the adsorption strength of reaction intermediates both on the Fe-N4 and Co-N4 sites, thus enhancing the ORR and OER activity, respectively. In addition, the PtFeCo/NC-based Zn-air battery delivers a higher power density than that of commercial Pt/C-RuO2, and can be steadily operated over 188 h.

In situ XPS proved effective charge transfer over ZIF-67@CoFe LDH S-scheme heterojunctions for efficient visible light driven hydrogen evolution

A binary catalyst ZIF-67@CoFe LDH with an S-scheme heterojunction mechanism and a framework structure is designed by a physical hybrid process. On the one hand, in situ irradiation X-ray photoelectron spectroscopy analysis showed that the internal electric field drove the photogenerated electrons in ZIF-67 to move towards CoFe LDH, forming an S-scheme heterojunction of ZIF-67@CoFe LDH, which greatly accelerates the separation of photo-generated carriers. On the other hand, the unique framework structure of ZIF-67 provides a large number of aiming points for the CoFe LDH nanorod clusters, effectively preventing the aggregation of CoFe LDH nanorod clusters. When CoFe LDH is aimed at the ZIF-67 surface, the unique 3D/2D structure of ZIF-67@CoFe LDH facilitates the mass transfer properties between ZIF-67 and CoFe LDH and enhances the absorption of visible light. In other words, the unique framework structure of ZIF-67 acts as a “scaffold”, which not only allows for a uniform dispersion of CoFe LDH, but also facilitates a stable loading of CoFe LDH onto the ZIF-67 surface. As a result, the binary catalyst exhibits excellent hydrogen evolution activity and stability. Under 5W (λ ≥ 420 nm) LED illumination, ZCF-15 (586.2 μmol g−1h−1) showed the best hydrogen evolution activity, which is 3.04 times higher than that of ZIF-67 (193 μmol g−1h−1) and CoFe LDH (192.7 μmol g−1h−1), respectively. After 25 h of cycling experiments, ZCF-15 still had 76% of the original amount of hydrogen evolution.