Carbon Nanotube Support Research Articles

Long-lasting copper carbon nanotubes for non-enzymatic electrochemical sensing of glyphosate

Accurate electrochemical detection of glyphosate (GLY) presents significant challenges due to its non-electroactive nature on conventional electrode materials. To address this challenge, copper-modified electrodes have been developed to form a complex with GLY, enhancing detection capabilities. In this study, we propose an innovative material: copper-modified carbon nanotubes on a glassy carbon electrode (Cu/CNT/GCE). The detection mechanism of GLY using Cu/CNT/GCE involves the formation of a copper-GLY complex, which inhibits the electrochemical response of copper, proportionally to the GLY concentration. This effect is enhanced by the synergistic interaction between copper and carbon nanotubes, increasing the electrochemical stability and detection capacity of the system. To evaluate the electrochemical performance of Cu/CNT/GCE, cyclic voltammetry was performed at different electrolyte concentrations and pH levels. Square wave voltammetry was employed for the electrochemical quantification of GLY, showing a linear correlation between GLY concentration and the inhibition of the copper response. The proposed sensor exhibited a low limit of detection (0.098 ppm) and a limit of quantification (0.326 ppm). Furthermore, the electrode demonstrated long-term stability, retaining 95 % of its signal after one year of storage. This stability is attributed to the carbon nanotube support, which prevents corrosion of copper particles. Recovery values ranged from 94 to 106 % for Citromax™ and Orium™ glyphosate with precision. The method showed excellent selectivity for GLY detection, even in the presence of other herbicides such as diuron and oryzalin. These properties suggest that Cu/CNT/GCE presents promising features for the electrochemical monitoring of GLY in diverse environmental samples.

Carbon Nanotube Support, Carbon Loricae and Oxygen Defect Co-Promoted Superior Activities and Excellent Durability of RuO2 Nanoparticles Towards the pH-Universal H2 Evolution.

This work reports a strategy that integrates the carbon nanotube (CNT) supporting, ultrathin carbon coating and oxygen defect generation to fabricate the RuO2 based catalysts toward the pH-universal hydrogen evolution reaction (HER) with high efficiencies. Specifically, the CNT supported RuO2 nanoparticles with ultrathin carbon loricae and rich oxygen vacancies at the surface (C@OV-RuO2/CNTs-325) have been synthesized. The C@OV-RuO2/CNTs-325 shows superior activities and excellent durability for the HER. It only requires overpotentials of 36.1, 18.0, and 19.3mV to deliver -10mA cm-2 in the acidic, neutral, and alkaline media, respectively. Its HER activities are comparable to that of the Pt/C in the acidic media but higher than those of the Pt/C in the neutral and alkaline media. The C@OV-RuO2/CNTs-325 shows excellent HER durability with no activity losses for > 500h in the acidic, neutral or alkaline media at -250mA cm-2. The density-functional-theory calculations indicate that the CNT supporting, the carbon coating, and the OVs can modulate the d-band centers of Ru, increasing the HER activities of C@OV-RuO2/CNTs-325, and stabilize the Ru atoms in the catalyst, increasing the durability of the C@OV-RuO2/CNTs-325. More interestingly, the C@OV-RuO2/CNTs-325 shows great potential for practical applications toward overall seawater splitting.

Molecular Solvation Environment Controls the Active Site in Cation-Mediated Electrocatalytic CO2 Reduction to Methanol

Electrocatalytic synthesis of higher-value products from waste molecules is an emerging technique for sustainable chemical catalysis. Heterogeneous molecular electrocatalysts are an important group of materials where the catalytic activity and selectivity can be controlled using molecularly defined active sites. Despite extensive efforts to synthesize better molecular catalysts, the effects of molecular aggregation, which dominates the interaction of the catalyst with the electrode surface as well as with the electrochemical solvation environment, are not fully understood. Using cobalt phthalocyanine (CoPc) dispersed on carbon nanotubes (CNTs) as a model system, we find that controlling the direct interaction of the molecular catalyst with cations in the electrochemical double layer (EDL) results in significantly enhanced performance for CO2 reduction (CO2RR). Specifically, molecular dispersion of the CoPc onto CNTs yields a 4-fold increase in total current density and 8-fold increase in methanol (MeOH) selectivity compared to aggregated CoPc physically mixed with the same CNT support, enabling CO2 to MeOH conversion with 42.34% Faradaic efficiency (FE). Using surface-selective sum-frequency generation (SFG) vibrational spectroscopy, direct detection of reaction intermediates reveals that the potential-dependent adsorption of two distinct CO intermediates at two types of active sites, one less active and producing mostly CO, the other more active and able to produce methanol. DFT calculations show that the CO intermediate responsible for selective MeOH production results from the direct interaction with cations present in the EDL. This interaction, which is only possible when CoPc is molecularly dispersed on the electrode surface, is responsible for the cation-assisted conversion of CO to MeOH. Control experiments using either strongly hydrated Li+, or chelated K+ by 18-crown-6-ether, which suppress MeOH formation, further confirms the important role of this interaction. Similarly significant enhancement effects are also observed for nitrate reduction reaction (NO3RR) and oxygen reduction reaction (ORR), showing that dispersing molecular catalysts into monomers states is a general design parameter required to enhance activity and selectivity by cation-assisted reaction kinetics inside the EDL.

Influence of Carbon Nanotube Support on Electrochemical Nitrate Reduction Catalyzed by a Cobalt Complex

Access to clean water is a pressing environmental and public health concern. Excess nitrate (NO3 -) from the overuse of fertilizer finds its way into our surface water and groundwater, which leads to adverse health effects such as cancer and causes significant damage to ecosystems.1-4 The electrochemical nitrate reduction reaction (NO3RR) has emerged as a promising water treatment approach to address this issue. The NO3RR involves the transformation of waste NO3 - into value-added nitrogen species, such as ammonia (NH3), via reduction. NH3 serves as a valuable chemical in various applications, including its use as a fertilizer, chemical precursor, fuel, and a potential hydrogen (H2) carrier for energy storage and transportation.5-7 Leveraging renewable energy, the NO3RR provides a sustainable approach to distributed NH3 production, which stands in stark contrast to the energy-intensive Haber-Bosch process.8-10 As a result, there is growing interest in designing catalysts for the selective reduction of NO3 - to NH3. However, this requires that we obtain a clear understanding of the role of each component in the catalyst structure.Molecular catalysts have unique advantages over other electrocatalytic materials due to their well-defined structures, which can be tailored through the choice of the metal center and ligands.11,12 Moreover, molecular catalysts can be immobilized on substrates to create heterogeneous electrocatalysts capable of achieving a high current density.13,14 In previous investigations, we showcased the efficacy of multi-walled carbon nanotubes (CNTs) as a catalyst support for electrochemical carbon dioxide reduction reactions.13,15 In heterogenized molecular catalysts, CNTs are generally believed to provide high surface area and electron conduction. However, our recent investigation reveals that CNTs can serve as catalysts themselves for the NO3RR,16 which expands our understanding of the diverse roles CNTs play in NO3 - reduction electrocatalysis.A major challenge in the field of electrocatalysis is the development of catalyst design strategies to control the reaction selectivity. We report on an underexplored approach to overcome this challenge by tuning the CNT support for a cobalt complex. With pristine CNTs as the support, the cobalt complex/CNT hybrid catalyst is selective for NO3 - reduction to NH3 with a maximum Faradaic efficiency of 70%. In contrast, the cobalt complex supported on oxidized CNTs (OCNTs) generates mostly H2 under the same conditions. On the basis of kinetic measurements which reveal that the rate-determining step of NO3 – reduction is limited by the first electron transfer without involving a proton, we propose that the oxygen functional groups on the OCNT support help deliver protons and steer the supported cobalt complexes from catalyzing NO3 - reduction to H2 evolution. The performance of both of these hybrid catalysts is compared with the controls of bare CNTs and OCNTs. Additional control experiments include tests conducted in the absence of NO3 -. These control experiments together with the rest of the experimental data provide strong evidence to support the notion that the product selectivity of the NO3RR catalyzed by cobalt complexes can be controlled via the CNT support. This study demonstrates the importance of tailoring the catalyst support to advance reactivity in catalysis for environmental remediation.

Tuning catalytical properties of Pd/MWCNT nanoparticles via precursor variation in supercritical carbondioxide deposition

A practical, stable and non-conventional supercritical carbon dioxide deposition precursor was used to prepare Pd/MWCNT nanoparticles. The bis(2,2’bipyridyl)palladium(II) chloride precursor has a similar solubility value to commercially used precursors while advantageously it can be reduced at moderate temperatures. Palladium nanoparticles, whose particle size distribution were estimated around 10.5 nm, was deposited on multi-walled carbon nanotube support at 80 ºC and under 20.6 MPa. The catalyst showed higher performance for the selected model Suzuki-Miyaura cross-coupling reaction when compared with a similar catalyst which was prepared under similar supercritical conditions but from a different precursor. In general temperature and pressure is the main parameters to tune material properties for this method. Hence, this study reveals how different precursors in supercritical deposition method may affect the material properties for the target applications.

Highly-efficient CoRuOx nanocatalysts for acidic oxygen evolution: The merit of optimum ordering degree of carbon nanotube support

Hydrogen production from proton exchange membrane water electrolysis is constrained by the sluggish kinetics of the anodic oxygen evolution reaction. RuO2 has attracted considerable attention due to its low reaction overpotential, but its inferior stability remains a major challenge. Herein, a strategy is proposed to enhance the catalytic activity and stability of CoRuOx nanoparticles by doping Co and regulating the ordering degree of carbon nanotubes (CNTs) by air annealing. It was found that the CoRuOx@CNTs-300 catalyst exhibited the best catalytic activity and stability when the annealing temperature was 300 °C. At the current density of 10 mA cm−2, the overpotential of this catalyst was only 201 mV, which was nearly 100 mV lower than that of commercial RuO2 (300 mV). Surprisingly, there was no significant increase in the overpotential when tested at a current density of 10 mA cm−2 for 50 h. The density functional theory calculations indicate that the high activity of the catalyst is due to the electronic coupling of CoRuOx nanoparticles and CNTs, and that the introduction of Co and CNTs improves the electronic structure and solvation energies of the Ru in the active site, dramatically increasing the structural stability.

Improving Pt Utilization and Electrochemical Activity of Proton Exchange Membrane Fuel Cells Through Surface Modification of Carbon Nanotube Catalyst Support

The main hindrances in commercializing hydrogen fuel cells are the high catalyst cost, sluggish oxygen reduction reaction (ORR) kinetics, and low durability over long cycling. Herein, a low‐Pt‐based efficient cathode catalyst decorated on nitrogen‐doped carbon nanotube (CNT) support is developed. The effect of N doping and chemical etching of CNTs on the performance of proton exchange membrane fuel cells (PEMFC) are demonstrated in this work. Half‐cell studies showed that Pt decorated N‐doped etched carbon nanotubes (Pt/NECNT) exhibit higher electrochemical surface area, onset potential, specific activity, and mass activity than Pt/CNT, Pt/ECNT, Pt/NCNT, and commercial Pt/C samples. In contrast to the commercial Pt/C catalyst, minimal loss in limiting current density and half‐wave potential is observed for Pt/NECNT catalyst even after the 10000th ADT cycle. From single‐cell study, the peak power density of 950 mW cm−2 and operational power density of 840 mW cm−2 (at 0.6 V) are obtained using Pt/NECNT cathode catalyst at 80 °C with low Pt loading. The remarkable enhancement in the electrocatalytic activity, kinetic property, and high durability of Pt/NECNT are ascribed to the N doping and surface modification of CNT support.

Electronic structure modification of metal phthalocyanines by a carbon nanotube support for efficient oxygen reduction to hydrogen peroxide.

An active and selective two-electron oxygen reduction reaction (2e- ORR) is required for efficient electrosynthesis of H2O2. This reaction can be promoted by metal phthalocyanines (MPcs), which serve as model catalysts with well-defined structures. MPc molecules have mostly been evaluated on conductive carbon-based substrates, including glassy carbon (GC) and carbon nanotubes (CNTs), yet their influence on the electrocatalytic properties is not well understood. This study demonstrated that the ORR activity per surface area was improved by up to 4-fold with MPc molecules supported on CNTs (MPc/CNTs, M = Co, Mn, and Fe) compared to MPc loaded directly on GC. Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that the CNTs modified the electronic structure of the MPc molecules to optimize the *OOH binding energy and boost the heterogeneous electron transfer rates. Detailed kinetic analysis enabled multiple reaction pathways to be decoupled to extract the metal-dependent intrinsic 2e-/4e- ORR activities. Finally, MPc/CNT catalysts were employed in an H2O2 electrosynthesis flow cell, which delivered an industrial-scale current density of -200 mA cm-2 and an H2O2 faradaic efficiency of 88.7 ± 0.6% with the CoPc/CNT catalyst in a neutral electrolyte.

Reaction characteristics of homogeneous and heterogenous reactions for glucose gasification in supercritical water using ruthenium catalyst supported on carbon nanotube

In this study, a spherical, Ru-based catalyst with a Carbon nanotube (CNT) support was used in a continuous-flow system, where homogeneous and heterogeneous reactions occurred simultaneously. Therefore, determining the homogeneous and heterogeneous reaction rates is important. Glucose (5 and 10) wt%, a typical model biomass compound, was chosen as the feedstock, and the reaction temperature was set at (500 and 600) ℃. The weight hourly space velocity was changed (40, 80, or 160) h−1 by maintaining the catalyst loading at 0.15 g and altering the flow rate (2, 4, or 8) mL/min. A reaction model where homogeneous and heterogeneous reactions proceed in parallel was developed, and the reaction rates were determined. The homogeneous reaction rate constants were (0.00968 and 0.0194) /s for (500 and 600) ℃, respectively, and the heterogeneous ones for Ru-based catalyst with a CNT support were (0.0137 and 0.0420) m3/(kg s) for (500 and 600) ℃, respectively.

Kinetic study of Ni-M/CNT catalyst in methane decomposition under microwave irradiation

Methane catalytic decomposition has been studied with catalysts that can attenuate the energy of electromagnetic waves to heat and drive the reaction. Herein, we report, for the first time, a comprehensive kinetic study of Ni-M (M=Pd, Cu, or Fe)-CNT catalysts under microwave irradiation. These binary metal alloy nanoparticles have been synthesized on multiwalled carbon nanotube support with solvothermal process. These catalysts showed incredible performance for both absorbing microwave energy and catalyzing the reaction to form carbon nanotubes and hydrogen. Ni-M-CNT has a reaction order of 0.74. 10Ni-1 Pd-CNT, 10Ni-1Cu-CNT, and 10Ni-1Fe-CNT have activation energies at 87, 75, and 69 kJ/mol. The investigation was carried out in a differential reactor. The results indicated that 10Ni-1Fe-CNT had the lowest activation energy due to the increase in microwave susceptibility. This work pioneered the microwave catalytic methane decomposition field as well as paving the way for future electrification of COx-free hydrogen production.

Strain enhances the activity of molecular electrocatalysts via carbon nanotube supports

Support-induced strain engineering is useful for modulating the properties of two-dimensional materials. However, controlling strain of planar molecules is technically challenging due to their sub-2 nm lateral size. Additionally, the effect of strain on molecular properties remains poorly understood. Here we show that carbon nanotubes (CNTs) are ideal substrates for inducing optimum properties through molecular curvature. In a tandem-flow electrolyser with monodispersed cobalt phthalocyanine (CoPc) on single-walled CNTs (CoPc/SWCNTs) for CO2 reduction, we achieve a methanol partial current density of >90 mA cm−2 with >60% selectivity, surpassing wide multiwalled CNTs at 16.6%. We report vibronic and X-ray spectroscopies to unravel the distinct local geometries and electronic structures induced by the strong molecule–support interactions. Grand canonical density functional theory confirms that curved CoPc/SWCNTs improve *CO binding to enable subsequent reduction, whereas wide multiwalled CNTs favour CO desorption. Our results show the important role of SWCNTs beyond catalyst dispersion and electron conduction.

The Effect of Reducing Agent for Synthesizing Palladium Nanoparticle on Carbon Nanotube Support and Its Superior Catalytic Activity towards Methanol Oxidation Reaction

In this report, we have synthesized carbon nanotube supported palladium nanoparticles (CNT-Pd) by using different reducing agents such as sodium borohydride (SBH), hydrazine monohydrate (HY) and ascorbic acid (AA) for the methanol oxidation reaction (MOR) in alkaline media. The elemental and morphological properties of all catalysts are verified by HRTEM, XPS, and XRD. From the HRTEM images, it is found that CNT-Pd reduced by sodium borohydride CNT-Pd (SBH) exhibited a narrow size distribution of Pd nanoparticles (PdNPs) with an average size of 3.15 nm. The role of the reducing agents (SBH, HY, and AA) is investigated by applying them as anode catalysts for the methanol oxidation reaction (MOR) and it is found that the reducing agent remarkably affected the electrochemical activities. CNT-Pd (SBH) catalysts show the superior catalytic activity and durability towards MOR among all catalysts, which may be due to the Pd NPs in CNT-Pd (SBH) having a perfect crystal structure with a narrow size distribution.

In situ x-ray absorption investigations of a heterogenized molecular catalyst and its interaction with a carbon nanotube support.

A highly active heterogenized molecular CO2 reduction catalyst on a conductive carbon support is investigated to identify if its improved catalytic activity can be attributed to strong electronic interactions between catalyst and support. The molecular structure and electronic character of a [Re+1(tBu-bpy)(CO)3Cl] (tBu-bpy = 4,4'-tert-butyl-2,2'-bipyridine) catalyst deposited on multiwalled carbon nanotubes are characterized using ReL3-edge x-ray absorption spectroscopy under electrochemical conditions and compared to the homogeneous catalyst. The Reoxidation state is characterized from the near-edge absorption region, while structural changes of the catalyst are assessed from the extended x-ray absorption fine structure under reducing conditions. Chloride ligand dissociation and a Re-centered reduction are both observed under applied reducing potential. The results confirm weak coupling of [Re(tBu-bpy)(CO)3Cl] with the support, since the supported catalyst exhibits the same oxidation changes as the homogeneous case. However, these results do not preclude strong interactions between a reduced catalyst intermediate and the support, preliminarily investigated here using quantum mechanical calculations. Thus, our results suggest that complicated linkage schemes and strong electronic interactions with the initial catalyst species are not required to improve the activity of heterogenized molecular catalysts.

Enhancing electrochemical performance of ultrasmall Fe2O3-embedded carbon nanotubes via combusting-induced high-valence dopants

• Ti 4+ , Sn 4+ , and Zr 4+ were successfully incorporated in Fe 2 O 3 by a flame synthesis. • The Fe 2 O 3 /CNTs nanocomposite was directly obtained by a flame synthesis. • Combustion reaction generating oxygen functional groups favor the wettability of electrode. • High-valence metal ions optimize the electron structure and enhance Na + adsorption. • The flexible Ti-FeO-CNT//MnO 2 achieved an exceeding high operating potential of 2.0 V. Doping is a reasonable solution to improve the electronic structure and surface properties of nanomaterials. Herein, we propose a rapid and simple methodology, flame synthesis, as an effective preparation strategy for incorporating high-valence metal ions (Ti 4+ , Sn 4+ , and Zr 4+ ) into ultrasmall Fe 2 O 3 on carbon nanotube support (i.e., M-FeO-CNT). The resulting materials exhibit not only a boosted Na + adsorption as shown by density functional theory (DFT) calculations, but also display an increased oxygen deficiency. The electrochemical activity and charge transfer efficiency of Fe 2 O 3 can be improved by reasonably substituting Fe 3+ with Ti 4+ , Sn 4+ , and Zr 4+ . The electrochemical investigation of Ti-doped Fe 2 O 3 (Ti-FeO-CNT) electrode demonstrates a splendid specific capacitance of 1.25 F cm −2 at 1 mA cm −2 in 1 M Na 2 SO 4 . This is significantly higher as compared to the capacitance of 0.48 F cm −2 . Flexible solid-state asymmetric supercapacitor Ti-FeO-CNT//MnO 2 is verified with operating voltage of 2.0 V and stability over 3000 cycles, and delivers a high energy density of 2.14 mWh cm −3 at power density of 25 mW cm −3 . The flame synthesis is expected to be widely applicable for the preparation of high-valence metal ions doped nanosized Fe 2 O 3 functionalized materials, thus opening up new avenues for energy and catalysis research.

Adjusting OH tolerance of Ni4 clusters supported on ultra-small carbon nanotube with lattice vacancies for hydrogen oxidation catalysts

The hydroxide (OH) binding on Ni4 clusters supported on the (5, 5) ultra-small carbon nanotubes (CNTs) with lattice vacancies is theoretically investigated by applying the density functional theory (DFT) method. All Ni4 clusters are strongly adsorbed on the (5, 5) ultra-small CNTs with lattice vacancies and formed very stable Ni4/Vn structures. The results show that the OH binding energy (OHBE) at a Ni site nearly increases linearly with increasing Ni d band center. On the other side, this OHBE also increases as the number of vacancies increases. These findings could be attributed to interactions with carbon dangling bonds, which alter the electronic structure of the CNT-supported Ni4 clusters. Furthermore, an unusual behavior is observed for a Ni4 cluster supported on the (5, 5) ultra-small without a vacancy, where its OHBE is noticeably stronger than the others. These assertions are also supported by the projected crystal orbital overlap population (pCOOP), the projected crystal overlap Hamiltonian population (pCOHP), and the Mulliken–Löwdin analyses, which confirm the presence of bonding, anti-bonding, and non-bonding of OH states on Ni4/Vn. As a result, we can conclude that OH strongly binds to all Ni4/Vn. Adjusting OHBE tolerance to the Ni4 clusters is regarded as evidence of the CNT support effect, resulting in an increase in the activity of the hydrogen oxidation reaction (HOR) catalyst in an alkaline environment. It is necessary to make the high performance of the Ni cluster catalysts.

Localized growth of atomic-layer-deposited platinum catalysts on plasma-treated surface of carbon nanotubes

Platinum–carbon nanotube (CNT) catalysts were evaluated for use as the cathode catalyst in polymer electrolyte membrane fuel cells. Pt catalysts were fabricated by atomic layer deposition (ALD) on bare untreated or O2 plasma treated CNTs. Pt formed as particles that uniformly covered both the bare and plasma-treated CNT supports. The Pt particles on the bare CNTs were relatively small, and the particle size increased with increasing number of ALD cycles. By contrast, Pt formed as sparsely deposited large particles on the plasma-treated CNTs. This morphological difference caused a clear difference in the electrochemical and fuel cell performance. Experiments confirmed that relatively high and stable power production can be obtained using the relatively large Pt catalysts grown on the plasma-treated CNTs. Factors other than electrochemical enhancement by the geometric features were also found to affect the fuel cell performance.

Carbon nanotube as catalyst support in supercritical water

Carbon nanotubes (CNT) are possible catalyst supports for biomass gasification. In this study, glucose (5 wt%), a typical model compound of biomass, was gasified with a 0.5 wt% ruthenium catalyst on a CNT support. Only 0.15 g of catalyst containing 0.5 wt% Ru was sufficient to achieve complete gasification. High stability was observed in supercritical water at 600 °C and 25 MPa using a packed bed reactor. Compared with previous studies, the amount of Ru used in this study was one to two orders of magnitude lower than that on other catalyst supports. This makes CNT a promising catalyst support for supercritical water gasification.

Optimization of olefins' yield in Fischer-Tropsch synthesis using carbon nanotubes supported iron catalyst with potassium and molybdenum promoters

Light olefins' (C2-C4) production from syngas (H2 +CO) through Fischer-Tropsch synthesis (FTS) benefits from Fe-based catalysts supported on carbon nanotubes (CNTs). Two-level full factorial design was applied for K and/or Mo-promoted Fe/CNTs catalyst to investigate the effects of synthesis conditions including Mo/K mass ratio, ultrasonic time, and iron loading on light olefins' yield. These catalysts were characterized to perform an in-depth study of Mo/K binary promoter effects on Fe/CNTs catalyst in Fischer-Tropsch to light olefins. CO chemisorption and TEM revealed that molybdenum plays a significant role in metal dispersion, leaving structural defects on CNTs support. Additionally, H2-TPR confirmed that K as promoter facilitates reducibility of Fe/CNTs catalysts, which promoted CO conversion in FTS. Compared with the un-promoted Fe/CNTs catalysts, addition of molybdenum as a promoter increased light olefins' selectivity by 33.4%, while potassium led to an increase in CO conversion by 96.3%. The optimum formulation (0.5K5Mo10Fe/CNTs) obtained olefins' yield of 35.5%.

Carbon nanotube supported Ga@PdAgCo anode catalysts for hydrazine electrooxidation in alkaline media

In this study, carbon nanotube supported (CNT) monometallic (Pd), trimetallic (PdAgCo), and multimetallic (Ga@PdAgCo) catalysts in different weight percentages (0.5–10%) are synthesized by the NaBH4 reduction method and characterized transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray diffraction (XRD) analytical methods. According to the TEM analysis results, while agglomeration doesn’t observe for 3% Ga@PdAgCo(80:10:10)/CNT catalyst, agglomeration is observed in certain parts for 7% Ga@PdAgCo(80:10:10)/CNT catalyst. The occurrence of agglomeration has a negative effect on catalytic activity. XRD analysis shows that as metal was added, the diffraction peaks are negatively shifted, thereby forming an alloy. Electrochemical measurements such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) are used for the hydrazine electrooxidation activities of the catalysts. The highest specific activity is achieved as 250.39 mA/cm2 (22592.66 mA/mg Pd) with catalyst. The electrochemical surface area (ECSA) of 3% Ga@PdAgCo/CNT catalysts is also calculated as 1392.43 m2/g. The homogeneous distribution of the metals on the support material and the alloy formation has an effect on the catalytic activity for the 3% Ga@PdAgCo(80:10:10)/CNT catalyst. Although Pd is an active metal on its own, the synergistic effect between them as a result of the formation of alloys with different metals and the electronic state change on the catalyst by adding different metals to Pd has a great influence on the catalytic activity. As a result, Ga@PdAgCo/CNT catalyst with its high current value stands out as a new anode catalyst for hydrazine electrooxidation.

Converting of kesambi (Schleichera oleosa l.) oil into biodiesel using ZnO-based solid acid catalyst

Alumina-supported zinc oxide-copper oxide (ZnO-CuO/γ-Al2O3) solid catalyst which coded ZCA and zinc oxide with multi-walled carbon nanotube support (ZnO/MWCNTs) coded by ZCNT catalyst have been successfully synthesized and used to produce biodiesel from Kesambi (Schleichera olesosa l.) oil. The catalyst was synthesized using a combination of precipitation and impregnation method based on a modified Stober gel-based process. Before being used for transesterification of kesambi oil, ZCA and ZCNT catalyst was characterized using N2 adsorption-desorption followed by Brunauer-Emmett Teller (BET) calculation and Scanning Electron Microscopy (SEM) analysis. The transesterification process was conducted in a glass batch-type reactor with refluxed methanol. The effect of loading ZnO (wt.% to catalyst support) on the yield of biodiesel was investigated. The results showed that the catalyst of ZCA was potentially used for the transesterification of kesambi oil. The highest biodiesel yield above 80% was achieved after 3 hours of transesterification.