Catalytic Stability Research Articles

Enhanced removal of tetracycline using three-dimensional electrochemical system with Fe/N/S co-doped coffee grounds biochar particle electrodes: Performance and mechanism

In this study, Fe/N/S co-doped biochar was prepared from coffee grounds for using as particle electrodes (PE) to construct a three-dimensional electrochemical system (3DES). Tetracycline (TC) was selected as the simulated contaminant to evaluate the performance of 3DES in removing trace organic contaminates form water. First, characteristics analysis revealed that the PE was the micron-level carbon-based solid material with good electric conductivity, excellent catalytic performance and stability. Then, the performance of the 3DES was evaluated. About 92% of TC and 76% of total organic carbon (TOC) was removed under optimal operation conditions of potassium peroxydisulfate (PDS) addition of 3mM, current density of 100mA·cm−2, PE dosage of 0.5g·L−1 and solution initial pH of 7. The 3DES exhibited satisfactory stability and application prospect for trace organic contaminates treatment in real water. Furthermore, analysis of the reactive oxidized species (ROS) revealed that the 1O2 and O2•− contributed much more to the TC removal than •OH and SO4•−. In addition, three possible pathways of TC removal in 3EDS was proposed. TC was degraded to organics with simple structures through functional group removal, ring-opening, and C=O bond rupturing, and finally mineralized into CO2, H2O, and NO3-, etc. Finally, toxicity evaluation of the intermediate products indicated that the ecological risks of TC was effectively reduced through 3DES. This study provided a new strategy for resource utilization of carbon-based solid waste and efficient treatment of refractory wastewater.

Fe3O4@SiO2‐APA‐Amide/Imid‐NiCl2 as a New Nano‐Magnetic Catalyst for the Synthesis of 4H‐Pyrimido[2,1‐b]benzothiazole Derivatives via MCRs Under Solvent‐Free Conditions

AbstractThis study presents the synthesis and characterization of a novel nano‐magnetic catalyst, Fe3O4@SiO2‐APA‐amide/imid‐NiCl2, designed for the efficient production of 4H‐pyrimido[2,1‐b]benzothiazole derivatives under environmentally friendly, solvent‐free conditions. The catalyst combines magnetic Fe3O4 nanoparticles with a silica shell and functionalized amide and imidazole groups, which enhance its catalytic activity and stability. By optimizing the reaction conditions, we achieved high yields of the target compounds while minimizing the environmental impact. The catalyst's magnetic properties facilitate easy separation and recovery, making it an attractive option for sustainable organic synthesis. The successful synthesis of the catalyst was confirmed through comprehensive characterization techniques, including X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrate that Fe3O4@SiO2‐APA‐amide/imid‐NiCl2 is a highly effective and reusable catalyst for the environmentally friendly synthesis of biologically relevant pyrimido[2,1‐b]benzothiazole derivatives, contributing to the advancement of green methodologies in organic chemistry.

Heterostructure of perovskite coupled graphitic carbon nitride for enhanced photodegradation under visible light

This study aimed to prepare and characterize LaFeO3 nanoparticles loaded graphitic carbon nitride (LFO/g-C3N4) photocatalyst and investigate the degradation of organic pollutants under UV and natural sunlight exposure. It is observed that LFO nanoparticles of an average size of about 67 nm were distributed on g-C3N4 sheets through chemical bonding owing to the formation of a composite. Compared to LFO and g-C3N4, composite has a good absorption ability to harvest more UV and visible light due to its large surface area and pore size. The photocatalytic studies revealed that the g-C3N4/LFO composite exhibits higher catalytic efficiency and stability for methylene blue (MB) degradation under UV and visible light. Under UV irradiation, the degradation efficiency of LFO, g-C3N4, and g-C3N4/LFO composite in synthetic wastewater was found to be around 50, 80 and 93 % with corresponding rate constants 0.05, 0.02, and 0.1 min−1 in 30 min, respectively. Under natural sunlight, the composite degraded 97 % of MB in 180 min with a rate constant of 0.016 min1. The higher photocatalytic activity of the composite was attributed to the interfacial charge transfer between LaFeO3 and g-C3N4, which are responsible for effective charge separation in the composite. Further, it has been investigated that singlet oxygen species (1O2) and hydroxyl radicals (•OH) are the main reactive species that contributed considerably to the complete degradation of MB. The nanocomposite was also demonstrated to be a stable catalyst and can be reused without any further modification.

Improving the catalytic activity and stability of Bacillus alcalophilus serine protease BAPB92 by rational design

Improving the catalytic activity and stability of Bacillus alcalophilus serine protease BAPB92 by rational design

Spherical Ru/FeOx composite as a bifunctional electrocatalyst for overall water splitting in neutral media

Electrochemical water splitting stands out as a promising technology for H2 production, due to its simplicity and high energy conversion efficiency. Therefore, it is a key issue to develop and design efficient catalysts for overall water splitting (OWS), especially in neutral media. Herein, the present study presents a stable bifunctional electrocatalyst, namely a spherical structure consisting of ruthenium and iron oxide composite supported on iron foam (Ru/FeOx), which was prepared using a simple two-step process. In 1.0M PBS, the optimized Ru/FeOx-300 demonstrates low overpotentials of 30 and 212mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10mAcm-2, respectively. More impressively, Ru/FeOx-300 requires only 1.505V to achieve a current density of 10mAcm-2 and exhibits superior electrochemical stability for 24h in a two-electrode neutral electrolyzer. The outstanding catalytic performance and stability of Ru/FeOx-300 nanospheres for water splitting are attributed to the binder-free integrated structure, the enhanced charge transfer facilitated and the synergistic effect between Ru and FeOx. This study offers a novel approach to the development of high-efficiency electrocatalysts for overall water splitting in neutral media.

Immobilization β-glucosidase from Dictyoglomus thermophilum on UiO-66-NH2: An efficient catalyst for enzymatic synthesis of kinsenoside via reverse hydrolysis reaction

Kinsenoside is a rare and valuable glycoside with extensive bioactivities. However, the enzymatic synthesis of kinsenoside has been a challenging task due to the limited enzyme toolbox and unsatisfactory yield. Herein, the β-glucosidase from Dictyoglomus thermophilum (DtBGL) was heterologously expressed, purified and enzymatically characterized. The purified DtBGL was successfully immobilized on the metal-organic frameworks of UiO-66-NH2. The DtBGL@UiO-66-NH2 was fully characterized using SEM, XRD, TGA and FTIR. The studies on enzymatic properties demonstrated that DtBGL@UiO-66-NH2 exhibited increased catalytic activity and stability compared to the free DtBGL. Particularly, DtBGL@UiO-66-NH2 could catalyze the synthesis of kinsenoside via the reverse hydrolysis reaction and the kinsenoside yield was 34.12 % under the optimized catalytic system, which was 1.9-fold higher compared with the free DtBGL. Moreover, DtBGL@UiO-66-NH2 displayed good reusability with a kinsenoside yield of 27.02 % after reuse for 3 times. The present work not only identifies and characterizes a highly active β-glucosidase with reverse hydrolysis activity, but also proposes the immobilized enzyme as an effective catalyst for the industrial production of glycosides.

Recycled industrial waste silicon steel as high-performance electrode for oxygen evolution reaction using electroless plating surface modification

Exploring the large-area, cost-effective, and high-performance electrocatalyticoxygen evolution reaction (OER) electrode for water splitting is of great significance. Inspiring from the ‘waste to resource’ toward the circular economy, herein, the waste silicon steels (SS) were transformed into high-performance CoxFe3-xP/SS OER electrode through a facile electroless plating method. The plating layer of CoxFe3-xP not only endows the CoxFe3-xP/SS with outstanding electrocatalytic OER activity but also improves the corrosion resistance and stability of CoxFe3-xP/SS. The obtained Co2Fe1P/SS electrode exhibits the lowest overpotential of 244 mV at a current density of 10 mA/cm2 in 1 M KOH with a low Tafel slope of 48.7 mV/dec. Even at high current densities and in 6 M KOH and alkaline seawater (seawater + 1 M KOH), the Co2Fe1P/SS electrode also shows relatively low overpotentials, as well as high long-term durability. Specially, a large-area Co2Fe1P/SS OER electrode(40 × 40 cm2)was successfully prepared via the electroless plating approach. Toward the CoxFe3-xP/SS, the bimetallic Co-Fe synergies and phosphating effect promote the exposure of active sites and charge transfer. In addition, generated M(OH)x/MOOH (M = Co or Fe) species during OER activation could synergize with CoxFe3-xP and contribute excellent catalytic activity and stability.

Boosted Photocatalytic CO2 Conversion of a Cs2AgBiBr6@Co3O4 Composite with High Activity and Selectivity under Low-Concentration CO2 and Natural Sunlight

To explore high-efficiency photocatalysts that can operate under low-concentration CO2 and natural light conditions remains a significant challenge in the field of photocatalysis. Here, we have constructed lead-free Cs2AgBiBr6@Co3O4 (CABB@Co3O4) composites with compact heterogenous interfaces, enhanced CO2 adsorption capability and excellent photoelectronic characteristics. The optimal CABB@Co3O4 heterojunction exhibits nearly 100% selectivity for visible-light-driven CO2 to CO conversion with the high catalytic efficiency and stability in high-purity and diluted CO2. Importantly, the CABB@Co3O4 photocatalyst is one of a few examples to drive photocatalytic CO2 reduction under the 5v% CO2 and natural sunlight, exhibiting a linear relationship between CO evolution rate and light intensity. The outstanding photocatalytic performance mainly originates from the suppressed carrier recombination and the decreased energy barrier for the formation of the key *COOH intermediate. This work provides prospective guidance for designing efficient photocatalysts toward CO2 conversion under the actual environmental conditions.

Iron and nickel based alloy nanoparticles anchored on phosphorus-modified carbon-nitrogen plane enhances electrochemical nitrate reduction to ammonia

The catalysts of iron and nickel nanoparticles anchored on carbon–nitrogen plane (FeNi-CN) are considered as the potential candidates for promising electrochemical nitrate reduction to ammonia (ENO3RR). However, the high d-orbital energy levels of iron and nickel sites coordinated with nitrogen atoms often lead to overly strong adsorption of reaction intermediates on active sites, severely limiting the improvement of catalytic performance. Herein, a catalyst FeNi3@P-NC consisting FeNi3 alloy nanoparticles confined in phosphorus (P)-modified carbon–nitrogen plane is successfully fabricated, where the electron withdrawal effect induced by P on the carbon–nitrogen plane decreases the d-orbital energy, and optimizes the d-band center of FeNi alloy, thus weakening the overly strong adsorption of intermediates at the metal-N sites and thereby improving NO3RR activity. The prepared FeNi3@P-NC catalyst exhibits exceptional NO3RR performance with a 93 ± 4.5 % Faradaic efficiency of NH3 production (FENH3) and a high NH3 yield rate (YNH3) of 9633 ± 227.3 μg h−1 cm−2 at −0.7 V versus Reversible Hydrogen Electrode (vs. RHE) under alkaline medium. Importantly, FeNi3@P-NC also demonstrates superior catalytic stability and durability, which maintains stability over twenty-five successive electrochemical cycles and for 50 h of continuous electrolysis at 100 mA cm−2.

Stability effects of alumina fibers on SnO2/Al2O3 NFs for efficient electrocatalytic performance towards CO2 reduction reaction

The weak stability of electrocatalysts seriously hinders the practical application in the field of electrocatalytic CO2 reduction reaction (CO2RR), so how to select catalyst supports and realize the ingenious combination between active sites and supports is still a challenge. In this work, alumina fibers (Al2O3 NFs) were employed to support Sn catalytic active sites with the aid of sol-gel methods and electrospinning. As-obtained SnO2-loaded aluminum oxide nanofibers (SnO2/Al2O3 NFs) catalyst possesses bulk-like SnO2 and nano-SnO2 loaded Al2O3 NFs. Interestingly, nano-SnO2 loaded Al2O3 NFs mainly contributes to the superior electrocatalytic properties towards CO2RR, particularly, faraday efficiency of formic acid (FEHCOOH) can reach 72.8% when the potential is -1.264 V, with HCOOH partial current density of 32.76 mA cm-2, and a long-term catalytic stability can be achieved. This study not only provides a new idea for enhancing the stability of electrocatalysts, but also expands the application field of Al2O3 NFs.

Hollow silicalite-1 encapsulated nickel nanoparticles as highly stable catalysts in maleic anhydride hydrogenation

Anchoring active metal particles in zeolite cages can significantly improve catalytic stability. In this study, hollow silicalite-1 (HoS-1) encapsulated Ni nanoparticles catalyst (Ni@HoS-1) was prepared using the impregnation method and applied in MA hydrogenation. The encapsulation mechanism was explained as the zeolite wall restricting the evaporation of water in HoS-1, hence Ni particles would be spontaneously enriched within the zeolite cage after drying and calcination. Experiments revealed the specially designed structure effectively protected Ni particles from leaching, and after 5 cycles in liquid-phase batch reactions, the final MA conversion of Ni@HoS-1 is 40.8 % higher than that of Ni/S-1 (85.5 % vs 44.7 %). Moreover, the low acidity of Ni@HoS-1 also delayed the accumulation of carbon deposits, extending the continuous reaction lifespan from 128 h of Ni/S-1 to 188 h. These findings provided a new perspective for the controllable locating of active metal sites against the supports.

Electrochemically assisted preparation of defect-rich Co3O4 electrocatalysts in a water-modified deep eutectic solvent for enhanced oxygen evolution in acid

Co3O4-based electrode materials exhibit great potential for utilization as efficient catalysts for the oxygen evolution reaction (OER), especially in acidic media. However, enhancing their catalytic stability remains a crucial challenge. Herein, we present a facile electrochemical deposition approach coupled with calcination treatment to achieve in-situ growth of active Co3O4 films from a deep eutectic solvent with water as the modifier. The incorporation of water optimizes the structure of fabricated Co3O4 by increasing oxygen vacancies and elevating the Co2+/Co3+ ratio, enabling it to sustain the OER in 0.5 M H2SO4. Impressively, the catalyst grown on Pt/Ti substrate exhibits stable operation over 125 h at 10 mA cm−2. Attenuated total reflection-fourier transform infrared (ATR-FTIR) spectroscopy reveals that OER on the defect-rich Co3O4 catalyst occurs through both lattice oxygen mediated mechanism (LOM) and adsorption evolution mechanism (AEM).

Anchoring atomic Pd on molybdenum disulfide with state-of-the-art specific activity in the electrochemical dehalogenation of florfenicol

The widespread discharge of halogenated organic pollutants (HOPs) in wastewater brings significant risks to the environment and human health due to potent high toxicity, antibacterial activity, and strong biodegradation resistance. Adsorbed atomic hydrogen (H*ads)-mediated electrocatalytic hydrodehalogenation (EHDH) has been recognized as an efficient strategy for HOPs removal through selectively breaking carbon-halogen bonds. In this work atomic Pd uniformly anchored on molybdenum disulfide (denoted as Pd-MoS2) was synthesized through a facile hydrothermal method and found with state-of-the-art specific activity in florfenicol (FLO) removal via the H*ads-mediated EHDH process. Pd-MoS2 completely dehalogenated (∼100 %) FLO within 30 min at a rate constant of 0.15 min−1, which was 6.0, 6.5 and 33.1 times the value of MoS2, Pd/C and carbon paper samples, respectively. Notably, the toxicity of the wastewater was reduced to 1/6 of its original value after the treatment. Moreover, Pd-MoS2 presented superior catalytic stability in five successive cycles. Furthermore, Pd-MoS2 was also robust in complex water environment with practical applicability for industrial wastewater treatment. A dual-active-center mechanism with enhanced H*ads production capacity and the improved H*ads utilization efficiency was contributed to the increased EHDH activity on Pd-MoS2.

Effective synergistic interaction between InZnZrOx ternary metal oxides and SAPO-34 molecular sieve catalysts for CO2 hydrogenation to light olefins

The synergistic interaction of metal oxides with molecular sieves is essential for the catalytic hydrogenation of carbon dioxide (CO2) into light olefins (C2=–C4=) over bifunctional tandem catalysts. Herein, a series of In2O3-doped InZnZrOx (IZZ) ternary metal oxides was prepared and physically mixed with SAPO-34. The bifunctional catalyst was used in the direct conversion of CO2 to light olefins. The relationship between IZZ oxide structures prepared using different methods and the catalytic performance of bifunctional catalysts was investigated. Moreover, the migration of InOx in ternary metal oxides was revealed. Results revealed that for IZZ oxides prepared via precipitation coating and impregnation, InOx species migrated to the SAPO-34 surface during thermocatalytic reaction due to the dispersion of In2O3 on the ZnZrOx surface and its weak interaction with ZnZrOx. This led to the neutralization of acid centers on SAPO-34 by InOx, thereby destroying the synergistic interaction between the oxides and SAPO-34, resulting in a large amount of unneeded methane and poor light olefin selectivity. However, the co-precipitated IZZ-CP oxides exhibited a ternary solid solution structure and inhibited the migration of InOx. This enhanced CO2 and H2 activation, affording more formate (HCOO*) and methoxide (CH3O*) intermediates that strengthened the synergistic interaction between the oxides and molecular sieves. After optimizing the In2O3 doping amount in IZZ-CP oxide and the reaction conditions, the IZZ-CP/SAPO-34 bifunctional catalyst achieved 17.9 % CO2 conversion, 80.1 % C2=–C4= selectivity, only 7.6 % methane and 44.6 % CO selectivity. It also maintained excellent catalytic stability without significant deactivation after continuous reaction for 80 h.

Dynamically Stabilizing Oxygen Atoms in Silver Catalyst for Highly Selective and Durable CO2 Reduction Reaction

AbstractOxide derived catalyst displays outstanding catalytic activity and selectivity in electrochemical carbon dioxide reduction reaction (CO2RR), in which, it is found that residue oxygen atoms play a pivotal role in regulating the catalyst's electronic structure and thus the CO2RR process. Unfortunately, the intrinsic thermodynamic instability of oxygen atoms in oxide derived catalyst under cathodic CO2RR potentials makes it unstable during continuous electrolysis, greatly hindering its practical industrial applications. In this work, we develop a pulsed‐bias technique that is able to dynamically stabilize the residue oxygen atoms in oxide derived catalyst during electrochemical CO2RR. As a result, the oxide derived catalyst under pulsed bias exhibits super catalytic stability in catalyzing electrochemical CO2RR, while keeping excellent catalytic activity and selectivity.

Rapid Preparation of Platinum Catalyst in Low-Temperature Molten Salt Using Microwave Method for Formic Acid Catalytic Oxidation Reaction.

In this paper, platinum nanoparticles with a size of less than 50 nm were rapidly and successfully synthesized in low-temperature molten salt using a microwave method. The morphology and structure of the product were characterized by SEM, TEM, EDX, XRD, etc. The TEM and SEM results showed that the prepared product was a nanostructure with concave and uniform size. The EDX result indicated that the product was pure Pt, and the XRD pattern showed that the diffraction peaks of the product were consistent with the standard spectrum of platinum. The obtained Pt/C nanoparticles exhibited remarkable electrochemical performance in a formic acid catalytic oxidation reaction (FAOR), with a peak mass current density of 502.00 mA·mg-1Pt and primarily following the direct catalytic oxidation pathway. In addition, in the chronoamperometry test, after 24 h, the mass-specific activity value of the Pt concave NPs/C catalyst (10.91 mA·mg-1Pt) was approximately 4.5 times that of Pt/C (JM) (2.35 mA·mg-1Pt). The Pt/C NPs exhibited much higher formic acid catalytic activity and stability than commercial Pt/C. The microwave method can be extended to the preparation of platinum-based alloys as well as other catalysts.

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Strong Metal‐Support Interaction between Pt and TiO2 over High‐temperature CO2 Hydrogenation

The catalytic activities and stability of oxide‐supported metal catalysts are significantly affected by metal‐support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal‐support interaction (SMSI) and electronic metal‐support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile‐supported Pt nanoparticles (NP) over high‐temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2−x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high‐temperature reverse water‐gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM‐1×h‐1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time‐on‐stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Unveiling the Activity Origin of Electrochemical Oxygen Evolution on Heteroatom‐Decorated Carbon Matrix

AbstractChemical modification via functional dopants in carbon materials holds great promise for elevating catalytic activity and stability. To gain comprehensive insights into the pivotal mechanisms and establish structure‐performance relationships, especially concerning the roles of dopants, remains a pressing need. Herein, we employ computational simulations to unravel the catalytic function of heteroatoms in the acidic oxygen evolution reaction (OER), focusing on a physical model of high‐electronegative F and N co‐doped carbon matrix. Theoretical and experimental findings elucidate that the enhanced activity originates from the F and pyridinic‐N (Py−N) species that achieve carbon activation. This activated carbon significantly lowers the conversion energy barrier from O* to OOH*, shifts the potential‐limiting step from OOH* formation to O* generation, and ultimately optimizes the energy barrier of the potential‐limiting step. This wok elucidates that the critical role of heteroatoms in catalyzing the reaction and unlocks the potential of carbon materials for acidic OER.

Enhancing Organic Pollutant Degradation Efficiency through a Photocatalysis-Electro-Fenton System via MoS2 Crystal Morphology Regulation.

A photocatalysis-electro-Fenton (PEF) system was constructed via molybdenum disulfide (MoS2) to remove tetracycline (TC) without an external oxidant supply and solution pH adjustment. In the system, original graphite felt (GF) was used as a cathode, from which H2O2 was in situ generated continuously under power. MoS2 was motivated by visible light to facilitate the cycle of Fe2+/Fe3+, enhancing the Fenton process to produce •OH. The experimental results showed that the system can increase the degradation rate of pollutants by more than 5 times. Moreover, the quenching and electron paramagnetic resonance (EPR) tests demonstrated that •OH was the dominant active species. X-ray photoelectron spectroscopy (XPS) characterization, Mo concentration, and cycle experiments proved the excellent catalytic activity and chemical stability of MoS2. It is worth mentioning that the photocatalytic performances of different morphologies of MoS2 (flower, flake, and radar) were compared. As a result, flower-like MoS2 exhibited a much superior photoresponse than flake and radar, which could accelerate the Fe2+/Fe3+ cycle further effectively. These findings highlight the morphology-performance relationship of MoS2 under a PEF system and the mechanisms of contaminant degradation, which is of great significance for developing photoelectric Fenton technology.