Low-cost Catalysts Research Articles

Green and clean synthesis of 4-arylideneisoxazol-5-ones using NaCl aqueous solution

The one-pot, three-component cyclization reaction a wide variety of aryl/heteroaryl aldehydes, hydroxylamine hydrochloride, and β-keto ester compounds was performed in a simple manner. The reactions carried out in the presence of sodium chloride (NaCl) as a profitable, green, and efficient catalyst at room temperature. Optimization experiments indicate that the amount of 17 mol% of loaded NaCl is sufficient to catalyze the reaction. Among the advantages of this NaCl-catalyzed method are availability of catalyst, no need for catalyst synthesis in several steps, commercially available reactants, use of aqueous conditions, clean synthesis, non-inflammable reaction medium, no environmental pollution, safety, cost-effectiveness, pot-economy, optimum efficiency, carbon efficiency, and economy of reaction steps. Due to the absence of harmful solvents, the use of sodium chloride as an abundant, low-cost, and useful catalyst, and the use of water as a solvent, this method is considered a green synthesis.

Temperature–Controlled hydrothermal hydrogenation of palmitic acid to alkanol or alkanes over Co@CN–x catalysts derived from ZIF–67

Biomass is one of the most abundant and important renewable resource. The selective hydrothermal hydrogenation of microalgae-based bio–oil to produce fine chemicals and fuels such as alkanols or alkanes has been widely studied in the past decade. However, developing a low–cost catalyst with high hydrogenation activity and hydrothermal stability remains a huge challenge. Here, we have constructed a new type of catalyst (Co@CN–900) to achieve highly selective preparation of alkanol (1-hexadecanol, 97.4 %, 220 °C, 30 min) and alkanes (composed of n-pentadecane, n-hexadecane, and cracking alkanes, 96.8 %, 280 °C, 300 min) from temperature–controlled hydrothermal hydrogenation of palmitic acid (a model compound of microalgae-based bio–oil). A large number of N–doped carbon nanotubes confined Co nanoparticles (NPs) catalysts are obtained through the simple one–step pyrolysis of ZIF–67. Catalysts with the special structures exhibit extremely high activity in the hydrothermal hydrogenation of palmitic acid, surpassing the commercial Pt/C catalyst, especially in the conversion rate of palmitic acid, the generation rate of 1-hexadecanol and n-hexadecane. More importantly, no significant deactivation was observed after 5 cycles, demonstrating relatively strong hydrothermal stability.

Boosting the oxygen reduction reaction activity of dual-atom catalysts on N-doped graphene by regulating the N coordination environment.

Development of low-cost and high-efficiency oxygen reduction reaction (ORR) catalysts is of significance for fuel cells and metal-air batteries. Here, by regulating the N environment, a series of dual-atom embedded N5-coordinated graphene catalysts, namely M1M2N5 (M1, M2 = Fe, Co, and Ni), were constructed and systematically investigated by DFT calculations. The results reveal that all M1M2N5 configurations are structurally and thermodynamically stable. The strong adsorption of *OH hinders the proceeding of ORR on the surface of M1M2N5, but M1M2N5(OH2) complexes are formed to improve their catalytic activity. In particular, FeNiN5(OH2) and CoNiN5(OH2) with the overpotentials of 0.33 and 0.41 V, respectively, possess superior ORR catalytic activity. This superiority should be attributed to the reduced occupation of d-orbitals of Fe and Co atoms in the Fermi level and the apparent shift of dyz and dz2 orbitals of Ni atoms towards the Fermi level after adsorbing *OH, thus regulating the active sites and exhibiting appropriate adsorption strength for reaction intermediates. This work provides significant insight into the ORR mechanism and theoretical guidance for the discovery and design of low-cost and high-efficiency graphene-based dual-atom ORR catalysts.

Synthesis of MnOOH and its application in a supporting hexagonal Pd/C catalyst for the oxygen reduction reaction.

With the expansion of global energy problems and the deepening of research on oxygen reduction reaction (ORR) in alkaline media, the development of low cost and high electrocatalytic performance catalysts has become a research hotspot. In this study, a hexagonal Pd-C-MnOOH composite catalyst was prepared by using the triblock copolymer P123 as the reducing agent and protective agent, sucrose as the carbon source and self-made MnOOH as the carrier under hydrothermal conditions. When the Pd load is 20% and the C/MnOOH ratio is 1 : 1, the 20% Pd-C-MnOOH-1 : 1 catalyst obtained by the one-step method has the highest ORR activity and stability in the alkaline system. At 1600 rpm, the limiting diffusion current density and half-wave potential of the 20% Pd-C-MnOOH-1 : 1 electrocatalyst are -4.78 mA cm-2 and 0.84 V, respectively, which are better than those of the commercial 20%Pd/C catalyst. According to the Koutecky-Levich (K-L) equation and the linear fitting results, the electron transfer number of the 20%Pd-C-MnOOH-1 : 1 electrocatalyst for the oxygen reduction reaction is 3.8, which is similar to that of a 4-electron process. After 1000 cycles, the limiting diffusion current density of the 20%Pd-C-MnOOH-1 : 1 catalyst is -4.61 mA cm-2, which only decreases by 3.7%, indicating that the 20%Pd-C-MnOOH-1 : 1 catalyst has good stability. The reason for the improvement of the ORR performance of the Pd-C-MnOOH composite catalyst is the improvement of the conductivity of the carbon layer formed by original carbonization, the regular hexagonal highly active Pd particles and the synergistic catalytic effect between Pd and MnOOH. The method of introducing triblock copolymers in the synthesis of oxides and metal-oxide composite catalysts is expected to be extended to other electrocatalysis fields.

A high-performance electrocatalyst via graphitic carbon nitride nanosheet-decorated bimetallic phosphide for alkaline water electrolysis.

Developing renewable and clean energy systems for overall water electrolysis requires low-cost, highly efficient, and stable catalysts. With this motivation, nickel cobalt phosphorus (NiCoP) was electrodeposited onto nickel foam (NF) and then modified with graphitic carbon nitride (g-C3N4). The designed g-C3N4/NiCoP/NF electrode was used for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline water electrolysis. It exhibited a small overpotential of 80 mV@10 mA cm-2 with a Tafel slope of 89 mV dec-1 for the HER. It also exhibited an overpotential of 370 mV@10 mA cm-2 with a Tafel slope of 64 mV dec-1 for the OER. The g-C3N4/NiCoP catalyst exhibited satisfactory stability in an alkaline electrolyzer system, in which g-C3N4/NiCoP/NF was used as the anode and cathode. Meanwhile, the electrocatalyst requires only a cell voltage of 1.70 V to achieve 10 mA cm-2 current density for overall water electrolysis.

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Transition metals anchored on nitrogen-doped graphdiyne for an efficient oxygen reduction reaction: a DFT study.

The search for highly active and low-cost single-atom catalysts for the oxygen reduction reaction (ORR) is essential for the widespread application of proton exchange membrane fuel cells. Transition metals anchored on nitrogen-doped graphdiyne (GDY) have attracted considerable interest as potentially excellent catalysts for the ORR. However, the relationship between the active site and nitrogen-doped GDY remains unclear. In this work, we conducted a systematic investigation of sp-hybridized N atoms anchoring single transition metal atoms of 3d and 4d on GDY (TMC2N2) as electrocatalysts for the ORR. Firstly, 18 kinds of TMC2N2 were determined to have good thermodynamic stability. Due to the extremely strong adsorption of *OH, TMC2N2 exhibits inferior ORR performance compared to traditional Pt(111). Considering that *OH adsorption hinders the catalytic activity of TMC2N2, we modified the OH ligand of TMC2N2 to develop the high-valent metal complex (TMC2N2-OH) aiming to enhance the electrocatalytic activity. The adsorption of intermediates on most TMC2N2-OH is weakened after the modification of the OH ligand, especially for the adsorption of *OH. Thus, by comparing the ORR overpotential of catalysts before and after ligand modification, we find that the catalytic activity of different TMC2N2-OHs improves to various degrees. MnC2N2-OH, TMC2N2-OH, and TcC2N2-OH exhibit relatively high ORR catalytic activity, with overpotentials of 0.93 V, 1.19 V, and 0.92 V, respectively. Furthermore, we investigated the cause of improved catalytic activity of TMC2N2-OH and found that the modified coordination environment of the catalyst led to adjusted adsorption of ORR intermediates. In summary, our work sheds light on the relationship between nitrogen-doped GDY and transition metal sites, thus contributing to the development of more efficient catalysts.

Synergistic self-driven and heterogeneous effect of a biomass-derived urchin-like Mn3O4/C3N4 Janus micromotor catalyst for efficient degradation of carbamazepine.

It is well known that obtaining efficient carbamazepine degradation materials or rapid carbamazepine-removal methods is still a challenge in the field of environmental remediation. Hence, the present study aimed to concurrently address these issues by combining a self-driven, heterostructured and low-cost biomass-templated urchin-like Janus micromotor catalyst for highly efficient carbamazepine degradation. The catalyst could autonomously move in a circle-like motion pattern via O2 bubbles generated from the Mn3O4-catalyzed decomposition of H2O2 with a velocity of 223.5 ± 7.0 μm s-1 in 1% H2O2. Benefiting from the well-structured heterojunction at the interface of C3N4 and Mn3O4, carbamazepine (CBZ) was degraded by 61% in 100 min under sunlight irradiation. In addition, density functional theory calculation results proved that the formation of the heterojunction structure promoted the generation of photo-generated carriers. Thus, the presented method provides a promising pathway for the rational construction and preparation of movable catalysts for the efficient removal of organic pollutants from wastewater.

High catalytic performance of thermally treated Mn-rich limonite for catalytic oxidation of toluene

Abstract The development of active and low-cost transition metal oxide-based catalysts was vital for the catalytic oxidation of toluene. This study aimed to prepare Fe-Mn oxide catalysts by Mn-rich limonite, and investigate the catalytic activity and mechanism for toluene oxidation. The natural Mn-rich limonite was thermally activated at different temperatures and these thermally activated samples exhibited different oxidation activities. YL-300, obtained through thermal treatment at 300°C, exhibited excellent catalytic activity, showing 90% toluene conversion at 239°C (1000 ppm toluene) and remarkable catalytic stability even in the presence of water vapor (5 vol.%). The amount of oxygen vacancies in the catalyst was regulated by tuning the thermal treatment temperatures. Optimal thermal treatment facilitated the increase of oxygen vacancies and enhanced the oxygen mobility and redox capacity of YL-300, contributing to the complete oxidation of toluene to H2O and CO2. The oxidation of toluene was greatly influenced by the adsorbed oxygen species. This study demonstrates the potential of Mn-rich limonite as a promising catalyst for toluene oxidation, thereby promoting the utilization of natural mineral materials in the field of environmental pollution control.

Investigation of waste-derived and low-cost calcium oxide-based catalysts in co-pyrolysis of EFB-HDPE to produce high quality bio-oil

This study evaluated and compared the bio-oil yield produced from the co-pyrolysis of empty fruit bunch (EFB) and high-density polyethylene (HDPE) feedstock using four calcium oxide (CaO)-based catalysts. Three catalysts were derived from waste sources, namely, clamshell (CS), eggshell (ES), and chicken bone (CB), whereas Malaysia dolomite (MD) was extracted from limestone. Pure CaO catalyst served as a control experiment for comparison purposes. Surface area (BET), particle size (PSA), X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) examinations were used to compare all catalysts. BET and PSA demonstrated that waste-derived catalysts (CS, CB, ES) have the properties required for co-pyrolysis to produce good yield and quality of bio-oil, whilst XRD and SEM/EDX revealed the existence of CaO compound in each of the catalysts. The co-pyrolysis of EFB-HDPE was performed under controlled conditions in a fluidized-bed reactor. All co-pyrolysis parameters such as catalyst loading, feedstock loading, gas flow, and temperature were fixed for all reactions. The study explored the effect of each catalyst on the catalytic cracking of EFB-HDPE through the bio-oil yield and hydrocarbon composition from the reaction. The chemical composition of the bio-oil samples was analyzed by gas chromatography–mass spectrometry (GC-MS) analysis, whereas the bio-oil yield was calculated using mass-balance equation. The maximum oil yield was 26.07 wt% for ES, whereas pure CaO generated a 52.39% hydrocarbon composition, the highest among all catalysts, followed by ES.

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Zn(OAc)2•2H2O- Catalyzed Synthesis of Chromeno[2,3-d] Pyrimidinones under Solvent-free Conditions

Due to their high synthetic efficiency, multi-component reactions (MCRs) have shown to be extraordinarily effective at producing compounds in a single synthetic operation. The chromeno[2,3-d] pyrimidine moieties represent important building blocks in synthetic bioactive compounds. The reaction of barbituric acid, aldehydes, and cyclohexane-1,3-diones in the presence of zinc acetate (5 mol%) under neat conditions at 70 0C, yielded a facile and one-pot synthesis of corresponding chromeno[2,3-d]pyrimidineones. Thirteen compounds containing neutral, withdrawing and electron donating groups (H, NO2, -CN, -Cl; -OH, -CH3 and -OCH3) were synthesized in good, isolated yields ranging from 78-91%. The successful involvement of o-, m-, and p- substituted nitro benzaldehydes suggested that steric hindrance had no effect. All of the synthesized compounds are well-known, and this process is unique in that it makes use of zinc acetate, an accessible, low-cost Lewis acid catalyst.

Theoretical exploration of the nitrogen fixation mechanism of two-dimensional dual-metal FeTM@GY (TM = Fe, Mo, Co, and V) electrocatalysts.

In contrast to the energy-consuming Haber-Bosch process, ammonia synthesis by electrocatalysis under ambient conditions is an efficient and environmentally friendly method. In this work, through first principles calculations, the potential of four dual-atom FeTM (TM = Fe, Mo, Co, and V) anchored graphyne (FeTM@GY) as efficient nitrogen reduction reaction (NRR) catalysts is systematically investigated. Among them, FeMo@GY is the most promising, with excellent NRR catalytic activity, high ability to suppress the competing hydrogen evolution reaction (HER), and good stability. Moreover, NRR prefers the maximum pathway with the calculated onset potentials of -0.27 V for FeMo@GY. This work not only suggests that FeMo@GY holds great promise as an efficient, low-cost, and stable dual-atom catalyst for NRR but also further provides a guiding idea for the design of efficient NRR catalysts.

Charting the electronic structure for discovering low-cost intermetallic catalysts

We utilize electronic-structure-based descriptors to screen stable and active intermetallic catalysts. Several novel catalysts are proposed for HER and ORR reactions and the effectiveness of descriptors has been thoroughly investigated.

Dense r-Ru/FeCoP heterointerfaces induced by a defect-assisted strategy for ultrastable alkaline overall water splitting.

Simplifying the anchoring process of Ru nanoparticles (NPs) and activating their bifunctional activity are challenges in the construction of Ru-based catalysts. In this work, FeCoP nanosheets anchored by Ru NPs (r-Ru/FeCoP) were innovatively synthesized using an oxygen defect-assisted-gas-phase phosphorization strategy. Surprisingly, the η100 values of r-Ru/FeCoP in the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes were 0.8 and 0.58 times those of Pt/C and RuO2, respectively. Notably, the rich Ru NPs as HER active sites on r-Ru/FeCoP enhanced the conductivity of the catalyst and promoted the reaction kinetics for HER, while the metal atoms on the FeCoP nanosheets served as OER active sites to accelerate the desorption of O2. The synergy between the two promoted the improvement of overall water splitting efficiency. Overall, this work provides a new approach for the development of low-cost bifunctional catalysts with high Ru utilization.

Waste ceramic frit as novel catalyst triggering sodium borohydride methanolysis reaction

Hydrogen energy is remarkable as a clean and efficient energy source alternative to fossil fuels. In recent years, hydrogen production from methanolysis of borohydride species has been the subject of many studies. Catalysts are of critical importance in hydrogen production with NaBH4. The widespread and commercial availability of this process depends on the cost and sustainability of the catalysts. Due to the cost and environmental impacts of metal-containing or metal-doped support materials used as catalysts, low-cost, environmentally friendly, and high-activity catalysts are being investigated. For this purpose, waste ceramic frits were used as catalysts in the NaBH4 methanolysis reaction. The hydrogen generation rates (HGR) of 11 different frits were compared. The oxide contents of these frits were determined by XRF analysis, and the two frits with the highest HGR values were characterized by XRD and SEM-EDX methods. For the two frits identified by code F1 and F2, initial rates of 10,027 mL/min.gcat and 8839 mL/min.gcat were obtained at 30 °C with 0.05 g catalyst and 1.25 % NaBH4, respectively. The activation energies of F1 and F2 frits were calculated as 18.27 kJ/mol and 29.71 kJ/mol, respectively.

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Optimization of Catalytic Pyrolysis Process of Waste Cooking Oil with a Low-Cost Carbonaceous Catalyst Using Central Composite Design of Response Surface Methodology

Tin-doped NiFe2O4 nanoblocks grown on an iron foil for efficient and stable water splitting at large current densities.

Developing low-cost and self-supported bifunctional catalysts for highly efficient water splitting devices is of great significance. Herein, different from previously reported NiFe2O4-based electrocatalysts, we have grown nano-NiFe2O4 directly onto the iron foil (IF) surface and in situ introduced Sn4+ into NiFe2O4. The resulting experimental phenomena confirmed that the as-synthesized Sn-NiFe2O4/IF can deliver large-current densities (>1000 mA cm-2) during oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) processes at a low overpotential. The needed overpotentials at the current density of 10 and 1000 mA cm-2 are 231 and 368 mV for OER and 57 and 439 mV for HER, respectively. Additionally, when applied for the two-electrode water splitting, the corresponding needed voltage for Sn-NiFe2O4/IF at the current density of 10 mA cm-2 was only 1.56 V, which was comparable to the commercial Pt/C-RuO2/IF electrode. Thus, the introduced Sn4+ greatly enhanced the electrocatalytic property of Sn-NiFe2O4/IF, resulting in a superior bifunctional catalyst that can be applied for large-scale hydrogen production.

Structural and compositional analysis of MOF-derived carbon nanomaterials for the oxygen reduction reaction.

The development of low-cost and efficient cathode catalysts is crucial for the advancement of fuel cells, as the oxygen reduction reaction (ORR) on the cathode is constrained by expensive commercial Pt/C catalysts and a significant energy barrier. Metal-organic frameworks (MOFs) are considered excellent precursors for synthesizing carbon nanomaterials due to their simple synthesis, rich structure and composition. MOF-derived carbon nanomaterials (MDCNM) inherit the morphology of their precursors at low dimensional scales, providing abundant edge defects, larger specific surface area, and excellent electron transport paths. Furthermore, the rich composition of MOFs enables the carbon nanomaterials derived from them to exhibit various physicochemical properties, including stronger electron gaining ability, oxygen affinity, and a higher degree of graphitization, resulting in excellent ORR activity. However, a more detailed analysis is necessary to understand the advantages and mechanisms of MDCNM in the field of the ORR. This review classifies and summarizes the structure and different chemical compositions of MDCNM in low dimensions, and provides an in-depth analysis of the reasons for their improved ORR activity. Additionally, the recent practical applications of MDCNM as cathode material in fuel cells are introduced and analyzed in detail, with a focus on the enhanced electrochemical performance.

Structural elucidation of Cr2O3-Al2O3 catalyst: Synthesis & characterization

The development of active, stable, and low-cost catalysts for efficient reactions is appealing but difficult. The objectives of this study are to synthesize Cr2O3-Al2O3 catalysts and analyze their physical properties using SEM, XRD, TGA-DTA, and FTIR. The impregnation method was used to create Cr2O3-Al2O3 catalysts with five different chromium oxide loadings (3wt%, 6wt%, 9wt%, 12wt%, and 15wt%). The physical properties of the catalysts were characterized using FTIR, SEM, BET, and TGA. The FTIR spectra and SEM images of the samples confirmed that Cr2O3 was successfully incorporated on Al2O3 support. TGA was used to evaluate the weight loss and thermal stability of the catalysts during the calcination process. The hydroxyl groups of alumina, as well as its water affinity, cause more mass loss when heated because water molecules are released. The addition of chromium oxide, on the other hand, alters thermal interactions, resulting in different mass loss behavior for chromium oxide alumina. The surface area changes seen by BET analysis gave insights into the structural flexibility of the catalyst across varied loading levels. The physical properties of synthesized catalysts demonstrated their ability to be utilized in a variety of catalytic reactions.