Powder Catalysts Research Articles

Cu2O Nanocrystal Model Catalysts

Comprehensive SummaryModel catalysts approach is widely adopted in fundamental studies of complex heterogeneous catalysis. Traditional model catalysts are single crystal‐based model catalysts, whose results, however, sometimes suffer from the “material gap” and “pressure gap” when applied to working catalysts. Recently, uniform catalytic nanocrystals with well‐defined structures have emerged, and we have put forward a concept of nanocrystal‐based model catalysts for fundamental studies of complex heterogeneous catalysis under conditions approaching working catalysts as closely as possible. In this perspective, we summarize our research progresses on Cu2O‐based nanocrystal model catalysts. Following a brief introduction, we summarize controlled synthesis of uniform Cu2O nanocrystals with various morphologies, morphology‐dependent surface compositions and structures and surface chemistry of uniform Cu2O nanocrystals, and heterogeneous catalysis of Cu2O‐based nanocrystals. Finally, we conclude the concept of nanocrystal‐based model catalysts and outlook that uniform nanocrystals can act not only as model catalysts but also as efficient catalysts. What is the most favorite and original chemistry developed in your research group?By far, the most favorite and original chemistry developed in my research group is the concept of “nanocrystal model catalysts”, which overcomes the so‐called “materials gap” and “pressure gap” encountered by the research field of surface chemistry for heterogeneous catalysis using traditional single crystal model catalysts.How do you get into this specific field? Could you please share some experiences with our readers?Surface chemistry studies of single crystal model catalysts had been considered to be able to achieve the fundamental understanding of complex heterogeneous catalysis before the “materials gap” and “pressure gap” were found to exist between single crystal model catalysts and working powder catalysts. Since then, to overcome the “materials gap” and “pressure gap” has been a main goal of the research field of surface chemistry for heterogeneous catalysis. I established my research group in 2004 when catalytic nanocrystals with uniform and well‐defined surface structures emerged quite a lot, and then had the idea of using nanocrystals as a novel type of model catalysts for fundamental studies of complex heterogeneous catalysis under conditions approaching workingcatalysts as closely as possible. Our work has successfully validated the concept of “nanocrystal model catalysts”. Therefore, my experience is to bear the important problems of the research field in mind and keep learning new knowledge from related research fields.What is the most important personality for scientific research?In my personal opinion, intuitivism, persistence, and self‐motivation are the most important personalities for scientific research.What is your favorite journal(s)?I prefer to publish my papers in journals that have large readerships so that the reported new knowledge can be widely shared.What are your hobbies? What's your favorite book(s)?My hobbies are the things that do not need thinking and special attention. These things make me truly relaxed. My favorite books are history of science with comments written by famous scientists (translated) in Chinese.If you have anything else to tell our readers, please feel free to do so.Scientific research is full of inter‐transformed frustration and happiness, but allows one to demonstrate the intelligence and capability freely and independently.

Considering the Influence of Polymer-Catalyst Interactions on the Chemical Microenvironment of Electrocatalysts for the CO2 Reduction Reaction.

The electrochemical CO2 reduction reaction (CO2RR) is an attractive method for capturing intermittent renewable energy sources in chemical bonds, and converting waste CO2 into value-added products with a goal of carbon neutrality. Our group has focused on developing polymer-encapsulated molecular catalysts, specifically cobalt phthalocyanine (CoPc), as active and selective electrocatalysts for the CO2RR. When CoPc is adsorbed onto a carbon electrode and encapsulated in poly(4-vinylpyridine) (P4VP), its activity and reaction selectivity over the competitive hydrogen evolution reaction (HER) are enhanced by three synergistic effects: a primary axial coordination effect, a secondary reaction intermediate stabilization effect, and an outer-coordination proton transport effect. We have studied multiple aspects of this system using electrochemical, spectroscopic, and computational tools. Specifically, we have used X-ray absorption spectroscopy measurements to confirm that the pyridyl residues from the polymer are axially coordinated to the CoPc metal center, and we have shown that increasing the σ-donor ability of nitrogen-containing axial ligands results in increased activity for the CO2RR. Using proton inventory studies, we showed that proton delivery in the CoPc-P4VP system is controlled via a proton relay through the polymer matrix. Additionally, we studied the effect of catalyst, polymer, and graphite powder loading on CO2RR activity and determined best practices for incorporating carbon supports into catalyst-polymer composite films.In this Account, we describe these studies in detail, organizing our discussion by three types of microenvironmental interactions that affect the catalyst performance: ligand effects of the primary and secondary sphere, substrate transport of protons and CO2, and charge transport from the electrode surface to the catalyst sites. Our work demonstrates that careful electroanalytical study and interpretation can be valuable in developing a robust and comprehensive understanding of catalyst performance. In addition to our work with polymer encapsulated CoPc, we provide examples of similar surface-adsorbed molecular and solid-state systems that benefit from interactions between active catalytic sites and a polymer system. We also compare the activity results from our systems to other results in the CoPc literature, and other examples of molecular CO2RR catalysts on modified electrode surfaces. Finally, we speculate how the insights gained from studying CoPc could guide the field in designing other polymer-electrocatalyst systems. As CO2RR technologies become commercially viable and expand into the space of flow cells and gas-diffusion electrodes, we propose that overall device efficiency may benefit from understanding and promoting synergistic polymer-encapsulation effects in the microenvironment of these catalyst systems.

Degradation performance and mechanism toward methyl orange via nanoporous copper powders fabricated by dealloying of ZrCuNiAl metallic glassy precursors

The catalyst of nanoporous Cu (NP-Cu) powders, with the chemical composition of Cu79.63Ni6.85O13.53 (at%), was successfully fabricated by dealloying of Zr–Cu–Ni–Al metallic glassy precursors. The as-prepared NP-Cu powders, co-existing with Cu2O phase on Cu ligament surface, had a three-dimensional network porous structure. The NP-Cu powders/H2O2 system showed superior catalytic degradation efficiency toward azo dyes in both acidic (pH 2) and neutral (pH 7) environments. Moreover, the cyclic tests indicated that this powder catalyst also exhibited good durability. A novel degradation mechanism of NP-Cu powders/H2O2 was proposed: the high degradation performance in acidic environment was mainly derived from heterogeneous reaction involved with a specific pathway related to Cu3+ to produce HO·, while in neutral environment it was primarily resulted from homogeneous reaction with the generation of HO· from the classical Cu-based Fenton-like process. This work indicates that the NP-Cu powders have great potential applications as catalysts for wastewater treatments.

In Situ Synthesis of Monolithic Cu2O–CuO/Cu Catalysts for Effective Ozone Decomposition

Nowadays, ozone (O3) has become a worldwide pollutant, and it is challenging to prepare monolithic O3 decomposition catalysts substituting the conventional complicated process of adhering catalyst powders onto porous substrates. Herein, monolithic Cu2O–CuO/Cu catalysts are obtained facilely by in situ thermal oxidizing–reducing copper foam. After optimization, the CuO nanowires (NWs) are first produced by annealing Cu foam in O2 at 400 °C for 2 h and then the NW surface is reduced into Cu2O by annealing in Ar/H2 at 350 °C for 2 h. The obtained Cu2O–CuO/Cu monolithic catalyst exhibits high catalytic activity to 20 ppm O3, maintaining 100% at a space velocity of 11,000 h–1 and even about 94% at 38,000 h–1. The catalytic ability toward O3 can be attributed to the generated Cu+/Cu2+ redox couples, the donor/acceptor-type point defects, and the Cu2O–CuO p–p heterojunction. This demonstrates the successful and convenient preparation of the monolithic catalyst for rapid, controllable, and productive O3 removal applications.

Polystyrene-NiO-CNT composite ball and film for photocatalytic degradation of methylene blue dye

Immobilization of photocatalysts on the solid support is important for environmental pollutant removal. We have prepared NiO-CNT composite photocatalyst following co-precipitation and catalytic pyrolysis method. The polystyrene-NiO-CNT composite film was prepared by adding 200 mg of NiO-CNT in 10 mL chloroform and different wt% (30%, 50%, and 70%) of waste expanded polystyrene (WEPS), and subsequently, the film was cast on a petri-dish with a film thickness of 0.45 mm. The charcoal balls (weight = 2 g, diameter = 2 cm) were coated with PS-NiO-CNT (30% PS) solution. The prepared photocatalyst powder, ball, and film, were compared for degradation of 100 mL methylene blue (MB) dye (10 mg/L). It was found that the powder and ball catalyst has exponential degradation, whereas the film catalyst has linear degradation nature. The powder sample (200 mg/100 mL) can degrade ∼ 96% of MB while a ball can degrade ∼ 86%, a film with 30% PS can degrade ∼ 81% within 4 h. The film and ball are magnetic, easily recyclable, and can be reused up to the 4th cycle without an appreciable loss (<10%) of degradation efficiency.

CuCeOx/VMT powder and monolithic catalyst for CO-selective catalytic reduction of NO with CO

The reaction path of a CuCe/VMT(M) catalyst in the CO-SCR reaction at N2O low temperature was found.

Effect of temperature and time for the production of polylactic acid without initiator catalyst from lactide synthesized from ZnO powder catalyst

Polylactic acid (PLA) is a biodegradable polymer that most importance at the present due primarily to its properties as biological degradation and biocompatibility derived from renewable resources. This study investigated the role of zinc oxide powder and tin(II) 2-ethylhexanoate as the catalysts for lactide and PLA synthesis, respectively. Polylactic acid was obtained by four stages: dehydration, oligomerization, depolymerization and ring opening polymerization. The catalyst was added and water was removed at the first stage then the reactions are carried out at different temperatures and reaction time on the other stages. The ratio of lactic acid and zinc oxide powder was 1000:3 for lactide synthesis, the ratio of lactide product and tin(II) 2-ethylhexanoate was 1000:4 for PLA synthesis without any initiator. The PLA products were analysed for the yield, some chemical and physical properties such as functional group, decomposition temperature, melting temperature of synthesized PLA. It is found that at reaction temperature of 160°C and reaction time for 5 h gave the highest yield PLA of 64.5% with its decomposition temperature of 311°C and melting point temperature at 152°C. There are two main mechanisms, polymerization and depolymerisation occurring in reaction and each mechanism plays a major role with respect to the reaction condition. At higher reaction temperature and longer time, the rate of depolymerisation is higher than that of polymerization leading to the lower of decomposition and melting temperature of synthesized PLA.

Diffusion measurements of hydrocarbons in H-MCM-41 extrudates with pulsed-field gradient nuclear magnetic resonance spectroscopy.

Mesoporous materials are promising catalysts for production of biofuels. Herein, H-MCM-41 catalysts with different concentrations of the silica Bindzil binder (10–50 wt%) were prepared and characterized using pulsed-field gradient (PFG) NMR in the powder form and as extrudates. Effective diffusion coefficients (De) are measured in all cases. Diffusivities of n-hexadecane were found smaller for extrudates as compared to the powder catalysts. The estimates of diffusive tortuosity were also determined. PFG NMR data showed one major component that reveals diffusion in interconnected meso- and micropores and one other minor component (1–2%) that may correspond to more isolated pores or may represent complex effects of restricted diffusion. Therefore, several approaches including initial slope analysis of spin-echo attenuation curves, two-component fitting and Laplace inversion were used to discuss different aspects of diffusional transport in the studied H-MCM-41 materials. Correlations between De and the amount of Bindzil, the specific surface area, the micropore volume, the particle size, the total acid sites and the Lewis acid sites are discussed.

Preparation of catalyst as Au doped Mn1Co9Ox/ceramic system for total oxidation of CO

In this paper, the Au doped Mn1Co9Ox was investigated for total oxidation of CO. The sol-gel method was applied to prepare this catalyst and some modern analysis methods as XRD, EPR, TPx, SEM were utilized to characterize its properties. The XRD patterns showed only Co3O4 phase without any peaks belonging to Mn or Au. However, the presence of Au and Mn was confirmed by EPR and O2-TPD results. With the aim to further apply catalyst in reality, the Au doped Mn1Co9Ox was deposited on ceramic by sol-gel, wet impregnation. The SEM images displayed the successful coating of active phase on substrate. However, the complete catalyst system didn’t have the high activity in total CO oxidation like the catalyst powder because of large agglomerations on coatings.

Block catalytic system for neutralization of carbon monoxide based on aerated concrete

The paper presents the results of a study of catalysts for the conversion of carbon monoxide based on aerated concrete, modified with magnetite and chromium ferrite separately and in aggregate. It was found that at a consumption of 100 g of catalyst powder per 1 dm3 of a typical mixture for producing aerated concrete and obtaining blocks of modified aerated concrete according to the traditional technology, their efficiency is 70-85% at 400 °C and decreases to 9-13% at 200 °C. In terms of strength and physicochemical properties, aerated concrete samples differ little from standard ones, and in some cases even exceed them. The proposed method for fixing catalyst particles in blocks of aerated concrete makes it possible to build fundamentally new schemes for neutralizing carbon monoxide when placing modified blocks directly at the loading of electrode raw materials in furnaces. This greatly simplifies the conversion process and its control system.

Industrial application of swirl regenerating micro-channel separation (SRMS) for fine catalysts removal from methanol-to-olefin quench water

Methanol to olefin (MTO) process is a chemical technology for producing low-carbon olefins from coal-based or natural gas-based methanol, which has changed the pattern of low-carbon olefins relying on petroleum cracking. However, a large amount of fine catalyst powders circulating in the water system of the MTO plant threats the sustainability of the process severely. Previously, a pilot-scale study about swirl regenerating micro-channel separation (SRMS) technology to remove the fine waste catalyst powders from MTO quench water was reported. In this study, the SRMS equipment was scaled up to an industrial level with a processing capacity of 400 m3/h based on the results of pilot-scale experiments, and the performance of the industrial unit was monitored for over 6 months. The results obtained directly from the industrial site showed that the SRMS unit based on deep-bed filtration and swirling flow enhanced washing and desorption could effectively remove the fine catalyst particles in the quench water, and the effluent particle concentration was maintained below 20 mg/L. Furthermore, the total oil content in the quench water reduced from 43.2 mg/L to 22.8 mg/L after being processed by the SRMS unit, which demonstrates that the SRMS unit also has an appreciable ability for oil pollutants removal. After the long-term operation of the SRMS unit, the equilibrium concentration of particulate matter in the quench water was reduced to under 50 mg/L, which significantly improved the performance of the quench water heat exchanger and effectively reduced the cleaning frequency of the heat exchanger, air cooler, and other equipment in the water system. Through the industrial-scale technical comparison, this technology outperforms the other common quench water treatment methods in equipment investment, maintaining cost, freshwater supplement, and energy consumption.

Catalytic co-pyrolysis of 5-Amino-1H-Tetrazole assembled with copper and boron powder: Pyrolysis kinetics and reaction mechanism

As a novel rich nitrogen content material, 5-Amino-1H-Tetrazole (5AT) has been considerably popularized in the propellants area recently. The pyrolysis is deemed as the prelude of combustion for solid phase 5AT, which plays a crucial role in combustion process and grasping the pyrolysis characteristics will be more beneficial to further explore the combustion properties of 5AT-based propellant. In this paper, several efforts have been made to enhance the pyrolysis behaviors of 5AT, including employing metal particles as catalysts, and modifying the surface treatment method. Due to the calorific value, the boron and copper powder are selected as the potential catalysts. The solvent/non-solvent (S/NS) and solution recrystallization method are compared to explore the impact of these two modification methods. TG-FTIR technique is applied to capture evolved signals of organic compounds to further deduce the most probable decomposition pathway. Moreover, model-free and model-fitting methods are both employed to calculate the kinetic parameters. The results reveal that, for the modified 5AT samples with the same boron powder catalyst, the activation energies and reaction model (all governed by F4) in the initial stage (100–330 °C) are not significantly impacted by these two modification methods. However, during the latter stages (400–750 °C), the catalytic actions of boron powder appear to be more active, and solution recrystallization method exerts better modification effect, the activation energies was reduced 18.3 kJ/mol and 10.9 kJ/mol respectively for the latter stages compared to S/SN method. Also, the reaction model is transformed from nth-dimensional model (D3) to nth-order model (F1) in the third stage. Particularly, the catalytic actions of copper powder results in the simplification of decomposition steps for 5AT, the activation energies was 138.8 kJ/mol and the catalytic effect of which was improved about 25% compared to the catalytic effect of boron powder in the first stage and its reaction model is also found to be changed into F3. It illustrates that copper powder could embody a better catalytic effect than boron powder under the same modification method. The conclusions of this study could provide a worthwhile guidance for the understanding, designs and applications of the 5AT-based propellants.

Novel powder catalysts of ferrocene-based metal-organic framework and their catalytic performance for thermal decomposition of ammonium perchlorate

It is of great significance to develop a novel and efficient combustion catalyst for thermal decomposition of ammonium perchlorates (AP) to regulate combustion performance of solid propellants. In this work, a series of ferrocene-based transition metals organic frameworks(MOFs) with 1,1′-ferrocenedicarboxylic acid (FcDA) as ligand, namely M-FcDA-MOFs (M = Co(II)、Mn(II)、Cu(II)、Fe(III) and Zn(II)), were successfully fabricated via simple solvothermal method. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The specific surface area and thermal stability of the samples were analyzed by N2 absorption/desorption isotherms and thermogravimetry (TG). Catalytic performance of the M-FcDA-MOFs towards the thermal decomposition of AP was investigated with differential scanning calorimetry-thermogravimetry (DSC-TG) techniques. The results show that the ferrocene-based MOFs have large specific surface area and high thermal stability, and can remarkably decrease the high temperature decomposition peak temperature (HTD) and apparent activation energy, enhance the apparent heat release of AP, and their catalytic performance is better than that of commercial combustion catalyst catocene. Among the samples investigated here, the Co-FcDA-MOF exhibited the best catalytic activity, which can decrease the HTD peak temperature and activation energy of AP by 90 °C and 20.4%, respectively, and increase the apparent heat release by 1082 J·g−1.

Highly controlled structured catalysts for on-board methanol reforming

The on-board methanol steam reforming (MSR) has long been considered as an effective approach to in-situ produce hydrogen for fuel cell vehicles (FCVs). However, the conventional MSR catalyst pellets suffer from easy breakage during the vehicle movement, leading to increased pressure drop and reduced system stability. Herein, we introduce an integrated method to prepare the highly controlled structured catalysts based on coupled processes: direct prototyping the structured substrate using digital light processing (DLP) 3D printing technology, in-situ dynamic crystallization of active components assisted by magnetic resonance imaging (MRI) and calcination. The synthesized catalyst owns a gradient layer of active component, and exhibits better MSR performance, higher mechanical strength, reduced pressure drop, higher Cu dispersion and better adhesion of active compounds when compared with the conventional powder and pellet catalysts. The demonstrated successful application proves the feasibility of developed method, which has great potential to be used for preparing precisely other monolithic catalysts with customized structures.

Facile preparation of lotus seedpod-derived magnetic porous carbon for catalytic oxidation of Ponceau 4R

In this research, magnetic porous carbon was directly synthesized through one-step pyrolysis of FeCl3 – lotus seedpod mixture. Properties of the obtained material were analysed by X-ray powder diffraction, SEM image, nitrogen adsorption isotherm and vibrating sample magnetometer. The results showed that magnetic Fe3O4 particles were successfully formed over material template in 1 hour. The magnetic porous carbon possessed the specific magnetization of 7.13 emu/g, high specific surface area of 288 m2/g and total pore volume of 0.18 cm3/g. The material was subsequently applied as a potential catalyst for Ponceau 4R degradation by H2O2. Parameters including pH, H2O2 concentration, and different types of catalysts were investigated. At pH 3, 200 ppm H2O2, and 0.40 g/L magnetic porous carbon, 83% Ponceau 4R 50 ppm was removed after 120 minutes treatment. Moreover, the catalyst powders were separated from the treated mixture easily by a magnet. Summarily, magnetic porous carbon can promise to be an efficient catalyst in decomposition of Ponceau 4R.

Catalytic ozonation membrane reactor integrated with CuMn2O4/rGO for degradation emerging UV absorbers (BP-4) and fouling in-situ self-cleaning

• The combination of CuMn 2 O 4 and rGO enhanced the catalytic ozonation. • Coating times and calcination temperature determined catalytic membrane properties. • [Ozone] and TMP affected the degradation of micropollutants significantly. • Self-cleaning and catalytic ozonation are catalytic ceramic membrane superiority. To develop degradation efficiency of emerging ultraviolet absorbers (benzophenone-4, BP-4) and in-situ self-cleaning of membrane fouling in membrane filtration, a novel CuMn 2 O 4 /rGO catalytic ceramic membrane (CR/CM) was fabricated and used in catalytic ozonation membrane reactor (COMR) for water purification. Firstly, the CuMn 2 O 4 /rGO powder catalyst was optimized, according to the performance of catalytic ozonation BP-4. After that, the potential reaction sites was proposed as surface oxygen defect in CuMn 2 O 4 /rGO. Secondly, the optimized CuMn 2 O 4 /rGO powder was deposited on the surface of ceramic membrane by the vacuum negative pressure method. The thickness and roughness of the active layer were adjusted by changing the coating times. The best fabrication condition was twice surface coating. The performance of this CR/CM mainly depended on [ozone] and transmembrane pressure (TMP). The optimum reaction parameters were [ozone] = 20 mg/L and TMP was 0.20 bar. Compared with the pristine ceramic membrane coupled with ozonation, the degradation efficiency of BP-4 increased by 61.3%, the self-cleaning efficiency of catalytic membrane was 52.87%. The proposed COMR, gave a full play to the respective advantages of membrane filtration and catalytic ozonation technology, including degrading micro-organic pollutants effectively and alleviating membrane fouling.

Architecting design of interface heating fabric evaporator and its application in clean water production

Given the problems in sewage treatment and clean water production, this study developed a solar steam generating device. Such a developed device comprised a superhydrophobic photocatalytic layer and a polypyrrole photothermal layer. To be specific, the superhydrophobic photocatalysts were capable of selectively adsorbing surface organic solvents and photodegrading dissolved pollutants, while the polypyrrole photothermal layer had a function of absorbing light energy and forming an interfacial heating layer to avoid heat loss. To improve the photodegradation ability, the photocatalyst of Bi2MoO6 was added, and its crystal structure and specific surface area were investigated specifically. The photocatalyst was supported on a fabric substrate to form a bulk material, thereby avoiding the defects of poor reuse of powder catalysts. After 8 cycles, the degradation efficiency remained higher than 98 %. In addition, the fabric exhibited an excellent mechanical stability, of which the average friction coefficient remains stable. Interestingly, after the sewage treatment, the fabric could act as the substrate of photothermal devices to ensure floating. The steam production efficiency was improved by the synergistic effect of the polypyrrole photothermal layer and the fabric.

Effect of Calcination on Shell Powder Catalyst Towards Effectiveness on Catalysing Transesterification of Crude Glycerol to Glycerol Carbonate

Valorisation of crude glycerol has gained much interest in the industry associated with the surplus of crude glycerol caused by the increase usage of biodiesel. Transesterification of crude glycerol using a heterogenous base catalyst is one of the effective ways to utilize the additional glycerol. Seawater clams commonly serve as a food source to us and the waste shells are a source of calcium carbonate that is abundantly available and can be converted into a heterogenous base catalyst for the transesterification process. Therefore, this study focuses on the utilization of catalyst synthesized from a species of seawater clam, Paratapes Undulatus in a transesterification reaction using crude glycerol (C.GLY) as a reactant together with dimethyl carbonate (DMC) to synthesize glycerol carbonate (GLYC). The catalysts are characterized using Field Emission Scanning Electron Microscope (FESEM), Attenuated Total Reflectance (ATR), Thermogravimetric Analysis (TGA), X-ray diffraction (XRD) and Particle Size Analyser (PSA). The product is characterized using Gas Chromatography (GC-FID). The performance of the synthesized shell catalyst with different calcination condition was studied. The reaction using the calcined shell catalyst is carried out at 75°C, molar ratio of 2 and 2wt% of catalyst for 1 hour. The catalyst that has the best performance is the shell catalyst that is calcined for 3h, which give the yield of 54.16%.

Influence of mixing time during glycine–nitrate process on the structural properties and reducibility of a dual-phase Ni–Cu–Mn spinel catalyst

The potential of Ni–Cu–Mn spinels as methane reforming catalysts for hydrocarbon-fueled solid oxide fuel cell (SOFC) applications is highly dependent on its catalytic properties, particularly reducibility. The reducibility of a spinel-structured catalyst is often correlated with its structural properties and fabrication processes. In this work, the structural properties and reducibility of a Ni–Cu–Mn spinel catalyst was evaluated on the basis of mixing time during the glycine–nitrate process. Phase analysis results showed that Ni 0.4 Cu 0.6 Mn 2.0 O 4 and (Cu, Mn) 3 O 4 in normal or inversed spinel structures were observed in GNP-produced Ni–Cu–Mn spinel catalyst powders. Distortion in inverse spinel structures enhanced the reducibility of the spinel catalyst. Morphological analysis results showed that complete nitrate binding occurred at a minimum mixing time of 24 h and resulted in homogenous particle size distribution and uniform elemental distribution. Furthermore, the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing was fully reduced at 450 °C. The reducing pattern of the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing time showed strong metal–support interaction and the fast adsorption of reactants. These effects were due to either the distribution of divalent cations in octahedral sites or large amounts of bulk pores. In conclusion, a minimum mixing time of 24 h is sufficient to produce the desired structural properties and reducibility of Ni–Cu–Mn spinel catalysts for SOFC applications.

Deposition of CaFe2O4 and LaFeO3 perovskites on polyurethane filter: A new photocatalytic support for flowthrough degradation of tetracycline antibiotic

The immobilization of powder catalysts on substrates has been the subject of increasing interest in the field of photocatalysis. For the first time, highly efficient LaFeO3 and CaFe2O4 perovskites were hydrothermally deposited on polyurethane filters (LFO/PU, CFO/PU). Furthermore, the photo-Fenton catalytic decomposition of tetracycline antibiotic by the new catalyst filters was explored under visible light irradiation. The structural, optical, and morphological characteristics of the photo-active filters were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), UV–visible diffusion spectra (UV–vis DRS), X-Ray fluorescence (XRF), and thermogravimetric/dynamic thermal analyses (TG-DTG). The decomposition studies were conducted in both batch and micro-flow reactor systems. The effects of solution pH, reactive species, and water type on the reaction mechanism were examined. It was found that the photo-Fenton degradation of tetracycline improved when the perovskite proportions on the filter were increased; the removal rates reached 94% and 80% forLFO/PU and CFO/PU, respectively. The high degradation performance obtained in lake (∼71%) and seawater (∼76%) demonstrated the great potential of photo-active catalyst filters, and their excellent stability was confirmed by reusability tests. In the continuous flow system, the photocatalytic filters kept the degradation rate stable at 83% and 44% after 7 h of examination forLFO/PU and CFO/PU, respectively. These results suggest that the as-prepared catalytic filters may be suitable for industrial photocatalytic applications.