Potential Catalyst Support Research Articles

Ti3C2Tx MXene-supported ruthenium nanoclusters for efficient electrocatalytic hydrogen evolution.

Developing an efficient and stable catalyst is both attractive and challenging for the electrochemical hydrogen evolution reaction (HER) due to the aggravation under the operating environment. MXene (Ti3C2Tx) is a potential catalyst support because of its abundant surface functional groups and unique hydrophilicity. However, anchoring noble metals onto MXene to construct high-performance electrocatalysts still presents some challenges. Herein, we present an MXene nanoparticle-supported Ru nanocluster (Ru@MXene-NP) electrocatalyst for HER. The Ru@MXene-NP not only effectively prohibits self-stacking but also ensures the full exposure of Ru nanoclusters. Thus, the Ru@MXene-NP catalyst exhibits an overpotential of 38.4 mV at 10 mA cm-2 and a Tafel slope of 26.4 mV dec-1 in an acidic medium, showcasing superior performance compared to most previously reported MXene-based catalysts. The small Tafel slope and low charge transfer resistance (Rct = 0.39 Ω) value indicate its fast electron transfer behavior. In addition, cyclic voltammetry curves and chronoamperometry tests demonstrate the high stability of Ru@MXene-NP. This work offers a novel perspective for designing catalysts by supporting noble metal nanoclusters on the MXene substrate's surface.

Polymer-derived SiOC ceramics: A potential catalyst support controlled by the sintering temperature and carbon content

A series of silicon oxycarbide ceramics with varying carbon content from ca. 10 wt% to ca. 40 wt% were prepared by thermal pyrolysis of four commercially available polysiloxanes and subsequent spark plasma sintering (SPS) at 1200 °C, 1400 °C, and 1600 °C. The results showed that the high carbon content led to a porous microstructure, and for SiOC with ca. 40 wt% carbon content, its porosity and specific surface area at 1600 °C reached 34% and 262 m2/g, respectively. The electrochemical behavior of materials was evaluated. It was shown that SiOC has a certain degree of electrocatalytic activity, and the sample with 10 wt% carbon content obtained at 1200 °C exhibited an overpotential of 450 mV vs. RHE at 10 mA·cm−2 in acid medium. Finally, it was analyzed that the electrochemical behavior of SiOC is closely related to the phase composition and microstructure of the resulting ceramics.

Highly Active Rh Catalysts with Strong π-Acceptor Phosphine-Containing Porous Organic Polymers for Alkene Hydroformylation.

Phosphine-containing porous organic polymers (phosphine-POPs) are a kind of potential catalyst support for alkene hydroformylation. However, the synthesis of phosphine-POPs with strong π-acceptor is still a challenge. Herein, we report the synthesis of phosphine-POPs with different π-acceptor properties [POL-P(Pyr)3, CPOL-BPa&PPh3-15, and CPOL-BP&PPh3-15] and evaluated their performances as ligands to coordinate with Rh(acac)(CO)2 for hydroformylation of alkenes. We found that the Rh center with stronger π-acceptor phosphine-POPs showed better catalytic performance. Rh/CPOL-BPa&PPh3-15 with strong π-acceptor bidentate phosphoramidites showed obviously higher activity and regioselectivity (TON = 7.5 × 103, l/b = 26.1) than Rh/CPOL-BP&PPh3-15 (TON = 5.3 × 103, l/b = 5.0) with weaker π-acceptor bidentate phosphonites. Particularly, the TON of the hydroformylation reached 27.7 × 103 upon using Rh/POL-P(Pyr)3 which possessed tris(1-pyrrolyl)phosphane coordination sites. Overall, our study provides an orientation to design phosphine-POPs for hydroformylation reactions.

On the Optimization of Ni/A and Ni/X Synthesis Procedure toward Active and Selective Catalysts for the Production of CH4 from CO2

Herein, optimization of zeolite NaA/NaX synthesis conditions in order to obtain the final product with high surface area and pore volume was investigated. An optimal synthesis condition was 5 days aging time and crystallization time of 9 h with the co-addition of cetyltrimethylammonium bromide (CTAB) and heptane. All those optimal synthesis conditions provided mixed phase between zeolite NaA and NaX, and addition of those organic phases improved the surface area and pore volume of the final synthesized zeolite. The role of CTAB and heptane on increasing the surface area of zeolite was studied by in situ small-angle X-ray scattering (SAXS). The SAXS results evidenced that small nucleation precursor was formed upon the addition of organic phase, and this nucleation precursor can provide zeolite with high-characteristic XRD signals of mixed phase of zeolite A and X after the crystallization process. The synthesized zeolite obtained from optimal synthesis condition with high surface area was further used as a catalyst support by impregnating with 5, 10, 15, and 20wt%Ni for catalyzing CO2 methanation reaction. The results found that 15wt%Ni/zeolite expressed the highest catalytic activity with high CH4 selectivity and stability. This was due to high dispersion of Ni species on catalyst surface and high metal-support interaction between Ni and zeolite. These results indicated that the mixed phase zeolite support can be a potential catalyst support for this reaction.

Catalytic Removal of NOx on Ceramic Foam-Supported ZnO and TiO2 Nanorods Ornamented with W and V Oxides

Energy consumption steadily increases and energy production is associated with many environmental risks, e.g., generating the largest share of greenhouse gas emissions. The primary gas pollution concern is CO2, CH4, and nitrogen oxides (NOx). Environmental catalysis plays a pivotal role in NOx mitigation (DeNOx). This study investigated, for the first time, a collection of ceramic foams as potential catalyst support for selective catalytic NOx reduction (SCR). Ceramic foams could be an attractive support option for NOx removal. However, we should functionalize the surface of raw foams for such applications. A library of ceramic SiC, Al2O3, and ZrO2 foams ornamented with nanorod ZnO and TiO2 as W and V oxide support was obtained for the first time. We characterized the surface layer coating structure using the XPS, XRF and SEM, and TEM microscopy to optimize the W to V molar ratio and examine NO2 mitigation as the SCR model, which was tested only very rarely. Comparing TiO2 and ZnO systems reveals that the SCR conversion on ZnO appeared superior vs. the conversion on TiO2, while the SiC-supported catalysts were less efficient than Al2O3 and ZrO2-supported catalysts. The energy bands in optical spectra correlate with the observed activity rank.

Carbon Nanofibers as Potential Catalyst Support for Fuel Cell Cathodes: A Review

Carbon Nanofibers as Potential Catalyst Support for Fuel Cell Cathodes: A Review

High surface area biochar from Sargassum tenerrimum as potential catalyst support for selective phenol hydrogenation

Biochar is a biomass-derived carbon-rich, highly porous, and renewable material, which can be used as catalyst support. In this study, high surface area biochar is prepared from Sargassum tenerrimum dry seaweed (SDSW) by the chemical activation method. The effect of variations in experimental conditions (KOH amount, carbonization temperature, activation time, and heating rate) on the physicochemical properties of activated biochar was investigated. Optimum activated carbon (SDSW-ABC) has been used as catalyst support for the preparation of Ni and Co based catalyst. Prepared catalyst (NiCo/SDSW-ABC) was characterized using BET, TGA, XRD, TPD, TPR, and TEM. Catalytic activity of NiCo/SDSW-ABC was evaluated for phenol hydrogenation at a wide range of temperatures (60–140 °C), hydrogen pressures (3–7 MPa), and reaction times (2–8 h) in various polar solvents. The catalyst demonstrated selective phenol conversion (≥99.9%) to cyclohexanol (≥99.9%) at 5 MPa, 100 °C, and 4 h in isopropanol. NiCo/SDW-ABC also explored for hydrogenation of few other lignin model compounds with different functionalities to evaluate the applicability of catalyst.

Three-dimensional hierarchical porous carbon structure derived from pinecone as a potential catalyst support in catalytic remediation of antibiotics.

In this study, pinecone was converted via two stage pyrolysis to produce low cost activated carbon. Furnace pyrolysis was used in the first step to convert pinecone to carbonized material, followed by microwave pyrolysis of the carbonized material activated with KOH to obtain activated carbon (ACK) materials as a suitable catalyst support. The ACK samples were characterized by their morphology, structural, adsorption and electrochemical properties. The optimized ACK 2.24-16 prepared from the pinecone had a complex three-dimensional (3D)-hierarchical porous structure, with an abundance of micropores and mesopores compared to other ACK samples judging from the high iodine number (1900 mg g−1) and the methylene blue number (4000 mg g−1) capacity. The optimized ACK 2.24-16 had the highest current response and least charge transfer resistance, along with moderate surface area (427 m2 g−1) as a promising photocatalyst support. The 3D hierarchical porous ACK significantly assisted catalyst dispersion, and enhanced visible light absorption and fast interfacial charge transfer. This work shows the promising aspect of utilizing pinecone to produce a low-cost photocatalyst support for environmental remediation.

CO2 hydrogenation over acid-activated Attapulgite/Ce0.75Zr0.25O2 nanocomposite supported Cu-ZnO based catalysts

A series of Cu-ZnO based catalysts supported on the Attapulgite/Ce0.75Zr0.25O2 (ATP-CZO) nanocomposite prepared by different methods were synthesized using impregnation method for CO2 hydrogenation to CO and methanol. The physicochemical properties and catalytic performance of these catalysts were investigated by N2 adsorption/desorption, XRD, FE-SEM, TEM, N2O chemisorption, XPS, H2-TPR and CO2-TPD techniques. Results showed that the ATP-CZO-SC-P400 nanocomposite prepared by polyethylene glycol (PEG 400) modified solution combustion (SC) method owned the best dispersion of CZO particles on the ATP-CZO composite. Due to the dispersing effect of PEG 400, the intensity of Ce0.75Zr0.25O2 solid solution was enhanced, and the interaction between Ce-Zr-O oxides and ATP support was improved. Furthermore, the formation of strong basic sites and copper surface area of the catalyst were enhanced. As a result, the CZFK/ATP-CZO-SC-P400 catalyst showed the highest yield of methanol and CO from CO2 hydrogenation. The intimate contact between metallic Cu sites and strong basic sites of ZnO, ATP-CZO composite and ZnO-CZO interfaces on the surface of catalyst was considered as an important factor. Attapulgite, with unique property, low cost and easy availability, is a potential catalyst support for CO2 hydrogenation reaction.

High conductivity of novel Ti0.9Ir0.1O2 support for Pt as a promising catalyst for low-temperature fuel cell applications

The novel nanostructured Ti0.9Ir0.1O2 acting as a potential catalyst support for Pt in fuel cell applications was easily synthesized by means of a facile and simple low-temperature hydrothermal process without using any surfactants and further heat treatment. Interestingly, even in low iridium doping concentration, the Ti0.9Ir0.1O2 support possessed the high electronic conductivity of 0.016 S/cm, which was ∼105 times as high as pure TiO2 (4.15 × 10−7 S/cm), suggesting the efficient doping of iridium into TiO2 lattice. Furthermore, the modified chemical reduction route utilized to prepare the 20 wt % Pt/Ti0.9Ir0.1O2 electrocatalyst exhibited the good anchoring and uniform distribution of Pt nanoparticles (NPs) (∼3 nm) over Ti0.9Ir0.1O2 surface and thus eventually resulted in the high electrochemical surface area (∼85.08 m2/gPt) compared to that of the commercial 20 wt % Pt/C (E-TEK) catalyst (∼69.21 m2/gPt). The cyclic voltammetry results in the methanol media revealed that the 20 wt % Pt/Ti0.9Ir0.1O2 displayed the superior electrocatalytic activity compared to the 20 wt % Pt/C (E-TEK) catalyst towards the methanol electro-oxidation. For instance, the 20 wt % Pt/Ti0.9Ir0.1O2 catalyst possessed the higher oxidation current density (∼28.8 mA/cm2), the lower onset potential (∼0.12 V) and the higher If/Ib ratio in comparison with the commercial 20 wt % Pt/C (E-TEK) catalysts. It is worth noting that the chronoamperometry results also indicated that the 20 wt % Pt/Ti0.9Ir0.1O2 exhibited higher durability than the commercial 20 wt % Pt/C (E-TEK) catalyst. Beside introducing novel Ti0.9Ir0.1O2 material, these results also offer a pathway of exploring the low dopants content of TixIr1-xO2 material to serve as a good catalyst support for many fuel cell applications.

Ruthenium nanoclusters distributed on phosphorus-doped carbon derived from hypercrosslinked polymer networks for highly efficient hydrolysis of ammonia-borane

Developing effective catalysts for hydrogen production from ammonia-borane (AB) hydrolysis is highly important for the potential usage of hydrogen-based energy. Here, phosphorus-doped carbon (PPC) derived from hypercrosslinked polymer networks of triphenylphosphine and benzene was employed as support to synthesize Ru/PPC through the in situ stabilization of ultrafine and uniform Ru nanoclusters (NCs). It was found that the Ru NCs with a mean diameter of 1.13 nm dispersed well on the PPC surface. The Ru/PPC exhibited a high turnover frequency of 413 mol H2 (molRu·min)−1 under mild conditions. The high catalytic performance of Ru/PPC could be ascribed to the small size of metal, which can offer more catalytically active components for the reaction. This work reveals that the PPC has promising potential catalyst support in stabilizing metal NCs for AB hydrolysis to generate hydrogen.

Recycling of red mud as a catalyst for complete oxidation of benzene

In this work, we investigated waste red mud (WRM) generated from industrial processes as a potential catalyst support for the complete oxidation of toxic organic compounds. Two different types of red mud based catalysts were prepared using calcination (CRM) and hydrochloric acid aqueous solution (HRM) pretreatments. In addition, HRMs loaded with different amounts of palladium were prepared and examined for their catalytic behaviors. For comparison, aluminas (γ-Al2O3) loaded with different amounts of palladium were also used. The catalyst samples prepared were characterized by using nitrogen adsorption, ICP-AES, TPR, XRD, FT-IR, and FE-TEM to examine their textural and chemical characteristics. The catalytic activity of the samples used depended on the pretreatment techniques applied, lattice oxygen mobility, the type of supports, and the loading amount of palladium. It was also interesting to note that water vapor in the feed stream inhibits catalytic activity for the complete oxidation of benzene.

Synthesis and Pore Structure Characterisation of Novel Mesoporous MgO-CeO<sub>2</sub>/SBA-15 as a Potential Catalyst Support

The high interest in the synthesis of mesoporous catalyst demands that novel materials are developed with simple methods capable of improving process yields. In this work, a novel heterogeneous mesoporous catalyst support has been synthesized using mesoporous SBA-15 loaded with mixed bimetal oxides of CeO2 and MgO. Formation of the SBA-15 was actuated in air at room temperature (25°C) and in oven conditions at 100°C after which cerium nitrate and magnesium nitrate precursors were then impregnated into the SBA-15 framework and calcined at 550°C for each of the air and oven crystallization processes. XRD peak patterns confirmed SBA-15 formation and dispersion of nanocrystallites of CeO2 and MgO within the porous framework of SBA-15. Both the air and oven dried processes produced mesoporous MgO-CeO2/SBA-15 catalysts with isotherms that exhibit typical H1 type hysteresis confirming that they possess open-ended cylindrical mesopores. The structural data extracted gave average pore size, pore volume and surface area values in the ranges of 3-5.2 nm, 0.600-2.500 cc/g and 400-500 m2/g respectively which is ideal for several industrial applications.

Investigation and modification of carbon buckypaper as an electrocatalyst support for oxygen reduction

The present study focused on a development of a buckypaper [a 45-µm-thick film composed of entangled Carbon nanotube (CNTs)] electrode or electrocatalyst support for oxygen reduction reaction (ORR). The surfaces of the pristine nanotubes in the buckypapers were functionalized by three well-known oxidative approaches: chemical, thermal, and electrochemical. Physical properties of the buckypapers and supported Pt electrocatalysts were characterized by thermogravimetric analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy (TEM). Electrochemical oxidation created the highest defect density as indicated by Raman data. In contrast, no significant change in surface functional group was observed after thermal oxidation. The TEM images revealed the successful deposition of Pt particles onto the buckypapers (35 wt% Pt/CNT) by an impregnation-reduction method, with average particle size between 2.5 and 3.5 nm. Electrocatalytic activity of the Pt electrocatalysts toward oxygen reduction was evaluated using a rotating disk electrode. The ORR results showed Pt electrocatalysts supported on the modified buckypaper displayed substantially enhanced ORR activity in comparison to the pristine Pt/buckypaper. The highest ORR activity at 0.85 V was ~5.3 mA cm−2. Our results demonstrated that buckypaper may be a potential catalyst support for fuel cell applications.

Study of Co-electrospun Nafion and Polyaniline Nanofibers as Potential Catalyst Support for Fuel Cell Electrodes

Nanostructured composites of electron and proton conducting materials were fabricated via simultaneous electrospinning of Nafion and PANI solutions on a rotating collector for application as fuel cell catalyst supports. Poly (ethylene oxide) (PEO) was used as a carrier polymer to enhance chain entanglements and therefore the electrospinnability of both solutions. Dual nanofiber mat with a Nafion/PANI composition of 50/50wt% was prepared. Post electrospinning annealing at 150°C for 5 mins and densification at 500 psi was performed to enhance Nafion domain crystallinity and fiber fraction (i.e. reduce void volume), respectively. PEO was selectively removed by treatment of the electrospun mats in boiling acid solution for one hour. Conductivity of the nanofiber mats was investigated using electrochemical impedance spectroscopy and equivalent circuit was used to decouple impedance from electron and proton transfer in the composite fiber mat. The resultant dual nanofiber mat exhibited an in-plane conductivity (σ=) of 0.014 and 0.023S/cm for electrons and protons, respectively. Through plane conductivity (σ⊥) was also studied and the dual nanofiber mat showed anisotropy for both proton and electron conductivities with (σ=)/(σ⊥)=1.27 and 1.4, respectively. Such dual nanofiber mats with percolating phases of both electron- and proton-conductors and three dimensional through–connected inter-fiber pore structure (for gas transport) can potentially serve as excellent catalyst supports for fuel cells.

Glycerol electrooxidation on highly active Pd supported carbide/C aerogel composites catalysts

The nanosized carbide supported on carbon aerogel composites have been synthesized by polycondensation of resorcinol and formaldehyde (RF) method in the presence of sodium tungstate and sodium molybdate. The materials are characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy (EDS), and cyclic voltammetry. The Pd nanoparticles supported on binary-carbide and carbon aerogel composites (Pd@WC-Mo2C/C) for glycerol oxidation are investigated for the first time. The Pd@WC-Mo2C/C as electrocatalyst shows a superior activity toward the glycerol oxidation in terms of the peak current density, which is almost two times higher than that of Pd/C and show better poison-resistant ability. The binary transition-metal carbide will be the potential catalyst support for the direct alcohol fuel cells.

On the transformation mechanism of K2Ti4O9 to TiO2(B) and formation of microvoids

TiO2(B), a potential catalyst support, has been synthesized from a support precursor, K2Ti4O9. High resolution electron microscopy revealed that the 32% volume loss in this transforma- tion is achieved by formation of facetted microvoids, around 10 nm in size, maintaining the morphol- ogy and size of the original crystals. A structural mechanism, including a hypothetical structure for a K2Ti2O5 intermediate, is suggested.