Cobalt-based Catalysts Research Articles

Engineering pyridinic-N-Co sites for enhanced CO2 hydrogenation to methanol

Regulation of hydrogenation capacity in cobalt-based catalysts is crucial for the effective conversion of CO2 into methanol. Herein, we developed a cobalt catalyst supported on nitrogen-doped carbon (viz., Co-N/C), specifically enriched with pyridinic N bonding to the cobalt sites. The hydrogenation capacity of the Co-N/C catalyst was carefully tuned by controlling the arrangement of pyridinic and pyrrolic N dopants through the ammonolysis treatment of the ZIF-67 precursor. The incorporation of pyridinic N significantly reduces electron localization around the cobalt centers, thereby minimizing unwanted hydrogenation to methane. The optimized Co-N/C catalyst, characterized by a predominance of pyridinic N, achieved a turnover frequency of 47.8h-1 for methanol production under 2MPa pressure and 180oC in a slurry reactor, surpassing the performance of a conventional Co/C catalyst featuring pyrrolic N by a factor of seven. Additionally, the Co-N/C catalyst exhibited excellent long-term stability, generating 70mmol of CH3OH and only 1.5mmol of CH4 over five cycles (totaling 30h). Both theoretical and experimental investigations revealed that pyridinic N has a greater affinity for bonding with Co compared to pyrrolic and graphitic N, and the pyridinic-N-cobalt serves as active sites for CO2 hydrogenation.

Dual active site pathways in cobalt-based bimetallic catalysts enhance oxygen evolution reaction activity: Density functional theory studies

Co single-atom catalysts show significant potential in enhancing oxygen evolution reaction (OER) efficiency, crucial for advancing renewable energy technologies. However, their performance is constrained by a single active site, making it challenging for traditional OER pathways to surpass theoretical overpotential limits. By focusing on dual active sites, this study systematically investigates the structural evolution and catalytic performance of Co based double atom catalysts using density functional theory. Co as the primary metal (M1), pairs with 15 different transition metals (M2) to create bimetallic catalysts. The formation energies, binding energies, and Gibbs free energy changes along four potential OER reaction pathways are calculated to assess the stability and activity of these catalysts. The results show enhanced catalytic performance along path II (H₂O → *OH → *2OH → *OOH → O₂) for Co-Ni, Co-Cu, Co-Pd, and Co-Pt catalysts. This improvement stems from synergistic interactions between metal atoms, bypassing high-energy barriers in traditional pathways. Notably, the d-band centers of Cu, Pd, and Pt near the Fermi level boost electron transfer. Co provides stable adsorption sites, optimizing the conversion of intermediates. This study advances understanding of the reaction mechanism and guides the development of more efficient catalysts.

Activating copper by creating low-coordinated copper sites for antibiotic detoxification through Electrocatalytic hydrodechlorination reaction

Electrocatalytic hydrodehalogenation (ECHD) offers a sustainable venue for detoxifying halogenated antibiotics by converting CX (XBr, Cl and F) bonds to CH bonds. Metallic copper (Cu) is a promising catalyst with higher chemical stability compared to general cobalt-based catalysts but suffers from lower activity toward dilute antibiotic pollutants. Herein, we activated the Cu by creating numbers of low-coordinated Cu sites on skeleton surface of a Cu foam electrode (r-CF) through a stepwise calcination and electrochemical reduction (C-ER) process. The r-CF electrode demonstrated extraordinary activity in FLO removal with a mass activity of 3.3 gFLO h−1 m−2. More importantly, it achieved 100 % conversion of CCl bonds at a relatively mild potential of −0.30 V, outperforming pristine Cu foam electrode (64.6 %) and most reported catalysts. Mechanistic studies revealed that the low-coordinated Cu sites exhibited an upshift d band center towards Fermi level, which facilitated pollutant adsorption and electron transfer on these sites. Furthermore, the C-ER processing increased the roughness of the skeleton, enlarging the laminar region in the vicinity of active sites and enhancing the turbulent state around the electrode during ECHD. These dual enhancement contributed to the mass transfer of FLO from bulk solution to electrode and their stabilization at active sites. The r-CF was further applied to detoxify a FLO-contaminated lake water sample. It was able to reduce the antibacterial activity of the water by 81.7 %. This work offered a new approach to activate the Cu for ECHD, and demonstrated the promise of Cu-mediated ECHD for antibiotics contamination remediation.

Open-loop response of Fischer–Tropsch reactions to manipulation of temperature and pressure

Abstract In the present work, the Fischer–Tropsch synthesis (FTS) is carried out through simulation. This reaction uses a gas mixture, called synthesis gas, composed of carbon monoxide rich in hydrogen (H2/CO > 2.5), to form medium and long chain hydrocarbons (C5 +). For the modeling of this system, a packed bed reactor with a cobalt-based catalyst has been considered, which promotes the polymerization of methylene species, selective to linear paraffins and 1-olefins. The objective of this work is evaluating the impact of operation variables, such as feed flows and temperature, coolant flow, system pressure, on the chain length distribution of the products. Current operating policies does not promote selectivity to the production of synthetic gasolines (C5–C12), because of the drastic increase in the temperature inside the reactor as consequence of the high exothermicity of the reactions (ΔH = −170 kJ mol−1). It has been impossible to maintain these reactions within the appropriate temperature range (475–520 K) without the presence of an external agent that manages the available heat, for this project molten sales have been proposed as a cooling medium (KNO3–NaNO3), based on its favorable heat transfer characteristics. By analyzing the system responses, the open loop model has allowed us to explore multiple hydrocarbon production scenarios, specifically highlighting the increasing of the yield of synthetic gasoline (48 wt%) in the products, from a defined molten salts (coolant) countercurrent flow range (7.05E-2 at 2.50E-1 m/h). It was noticed that this heat management allowed us to obtain a specific range of hydrocarbons, representing the opportunity to control the growth of the chain length. In conclusion, this analysis will lay the foundations for the design control policies, which help to increase current yields of synthetic gasoline, making it possible to achieve the desired quality for the immediate future.

Catalysts screening on production of syngas over novel cobalt-based catalysts supported with dolomite: effect of calcination temperature and Co loading

Catalysts screening on production of syngas over novel cobalt-based catalysts supported with dolomite: effect of calcination temperature and Co loading

Leveraging interlocking structural defects of g-C3N4/CNT networks: Toward enhanced oxygen reduction activity of the cobalt-based electrocatalyst

Carbon-based transition-metal electrocatalysts are regarded as promising candidates for catalyzing oxygen reduction reaction (ORR), yet their electrocatalytic ORR performances are greatly limited by active sites utilization caused by the metal aggregation and pore collapse under high temperature. This study rationally designed a cobalt-based ORR catalyst supported on a g-C3N4/carbon nanotube (CNT) network as a cost-effective alternative of platinum-based catalysts. CNT were embedded into the lamellar precursor of melamine and cyanuric acid, and a synergistic effect between CNT and precursor was realized to regulate the density and activity of active sites. The polycondensation of precursors led to the formation of an "interlocking" structure of CNT supports with abundant exposed defects, allowing for effectively anchoring cobalt ions to generate Co-Nx sites. Meanwhile, partial Co ions underwent reconstruction and transportation to form Co nanoparticles and extended the disruptive CNT structure, exposing more interfacial defects to enhance the ORR catalytic properties. The prepared Co@g-C3N4/CNT catalyst demonstrated impressive ORR activity comparable to commercial Pt/C catalyst, showing superior stability. This research offers a promising approach for engineering interfacial defects to synthesize high-performance non-precious metal electrocatalysts for energy conversion applications.

Lewis Acid Sites in Hollow Cobalt Phytate Micropolyhedra Promote the Electrocatalytic Water Oxidation.

The acid-base microenvironment of the metal center is crucial for constructing advanced oxygen evolution reaction (OER) electrocatalysts. However, the correlation between acidic site and OER performance remains unclear for cobalt-based catalysts. Herein, Lewis acid sites in hollow cobalt phytate micropolyhedra (M-CoPA, M = Cu, Sr) were synthesized by a cation-exchange strategy, and their OER performances were studied systematically. Experimentally, Lewis acid Cu2+ sites with stronger Lewis acidity exhibited superior intrinsic activity and long-term stability in alkaline electrolytes. The spectroscopic and electrochemical studies show Lewis acid sites in hollow cobalt phytate micropolyhedra can modulate the electronic distribution of the adjacent cobalt center and further optimize the adsorption strength of oxygenated species. This study figures out the effect of Lewis acid sites on the OER kinetics and provides an effective way to develop high-efficiency electrocatalysts for energy conversion systems.

Direct CO2 hydrogenation over Na and CeO2-promoted Iron and Cobalt-based Catalysts Supported on MCM-41

This contribution has studied iron or cobalt-based Fischer-Tropsch catalysts, promoted with CeO2 and Na and supported on MCM-41 mesoporous silica in the direct CO2 hydrogenation to hydrocarbons. The cobalt-based catalyst is more active in the presence of ceria as a promoter, presenting long-chain hydrocarbons under reaction conditions of 350 °C, 40 bar, H2/CO2 = 3, and GHSV = 6000 mL g-1 h-1. The characterization of the catalysts suggests that CoCeNa/M exhibits a strong Co-O-Si bond formation, preventing the cobalt oxide reduction to Co2+ species, which can be associated with methane production. On the other hand, iron-based catalysts present higher CO and CH4 concentrations, as shown via in situ DRIFTS, suggesting a possible iron carbide phase, which can be formed by the severe FTS reaction conditions, producing a high concentration of water and competing with Sabatier reaction.

A bifunctional catalyst for direct CO2 conversion to clean fuels: Mechanistic insights and a comprehensive kinetic model

The escalating global concern over CO2 emissions has spurred extensive research aimed at developing innovative solutions for capturing, storing, and utilizing CO2, crucial for establishing a closed carbon loop. Thermo-catalytic CO2 hydrogenation stands out as a promising approach, though challenged by CO2's high stability, hindering the production of heavy liquid hydrocarbons. This study explores the design and performance of a bifunctional cobalt-based catalyst, promoted by Ru and supported by multiple shells of carbon, mesoporous silica, and ceria for CO2 hydrogenation in the Modified Fischer-Tropsch Synthesis (MFTS) route. Through meticulous characterization and evaluation, the catalyst demonstrates suitable textural properties, reducibility, and dispersion of active sites, promoting CO2 conversion and selectivity towards heavier hydrocarbons, highlighting the significance of catalyst design and operating conditions. The catalyst exhibits notable stability across catalyst deactivation, attributed to its thermal conductivity provided by SiC matrices. SiC-supported catalysts play a pivotal role in enhancing the efficiency, selectivity, and stability of CO2 hydrogenation catalysts. Moreover, in this study, through meticulous evaluation of elementary reactions based on molecular dynamic (MD) computations, a detailed mechanism for MFTS is presented. Key to this mechanism is the H-assisted CO2 dissociation pathway, supported by computational analysis. The pathway involves sequential reactions starting from CO2 adsorption on catalyst sites, followed by successive transformations leading to the formation of hydrocarbon building blocks. Ultimately, a developed MFTS kinetic model based on the MD-evaluated mechanism, which accurately predicts product selectivity across various operational conditions, indicating its robustness and reliability, is presented.

Ultrastable cobalt-based chainmail catalyst for degradation of emerging contaminants in water

Developing stable and efficient cobalt-based catalysts for degradation of emerging contaminants (ECs) in water is deemed as a practical strategy to avoid secondary pollution in advanced oxidation processes (AOPs). Herein, we developed a ultrastable cobalt-based chainmail catalysts (Co-NC900) using 2, 2’-bipyridine-assistant pyrolysis method. More than 96.6 % of imidacloprid (IMD) in water could be degraded within 5 min in the presence of Co-NC900 and peroxymonosulfate (PMS). Amazingly, Co-NC900 still give 95 % degradation efficacy for IMD after15 runs. And only 0.083 μg L−1 of Co could be detected in the reaction mixture after continuous using 7 d. Density Functional Theory (DFT) calculations demonstrated that Co-NC900 can efficiently activate PMS through unique ping-pong mechanism (C-N bond breaking and re-forming process), and further degrade ECs. This study presents a novel approach for the development of efficient and stable metal-based catalysts for the removal of ECs from water.

Sulfonated Covalent Organic Frameworks Anchoring Cobalt as High-Efficient and Stable Catalysts for Peroxymonosulfate Activation.

Heterogeneous cobalt-based catalysts are highly effective in activing peroxymonosulfate (PMS) and produce free radicals to deal with recalcitrant organic pollutants in water. However, unfeasible recyclability and gradual performance degradation remain challenging due to the easy agglomeration and leaching of active cobalt species. Herein, a strategy is proposed to construct stably anchored and highly dispersed Co2+ sites on dual functional sulfonated covalent organic frameworks (COF-Co). The sulfonic acid groups are able to realize the targeted binding with cobalt ions through a two-step cation-exchange method, leading to strong combination with active Co2+ sites and utmost utilization efficiencies. Moreover, the super-hydrophility of sulfonic acid groups favors the rapid accessibility of organic molecules to the catalyst and accelerates the degradation. Remarkably, COF-Co exhibits high activity in PMS activation, effective oxidation for tetracycline degradation (92% within 30min at 30mg L-1) and other coloring contaminants, and excellent recycle stability. This work can guide the rational design of efficient and environmentally friendly PMS-activated catalyst with great potential for application in wastewater treatment.

Efficient Adsorption and Degradation of Tetracycline Hydrochloride Using Metal-Organic Framework-Derived Cobalt-Based Catalysts and Mechanism Insight.

High-performance Co-based catalysts were derived by pyrolysis using synthesized MOFs as self-sacrificial templates. Various catalytic systems were constructed by peroxymonosulfate (PMS) to degrade tetracycline hydrochloride (TC). Adsorption-degradation efficiencies, cycle performance, dynamics, and the adsorption catalytic mechanism of various catalytic systems for TC were studied. The effects of different synthetic solvents, pyrolysis temperatures, and single/bimetallic element compositions on degradation efficiency were innovatively compared. The optimal catalyst and PMS dosage for the experiment were determined to be 10 mg and 0.1 mL, respectively. The results indicated that all catalytic systems could efficiently degrade TC and have a high acid-base resistance. The catalyst activity was significantly influenced by the pyrolysis temperature. The optimum pyrolysis temperatures for Zn@Co-N-C-T, CH3OH@Co-N-C-T, and H2O@Co-N-C-T were 1000, 900 and 900 °C, respectively. More abundant pore structures and active sites were generated in Zn@Co-N-C-1000, exhibiting an excellent TC degradation efficiency and adsorption capacity, achieving 94.73% and 167.564 mg/g, respectively. Meanwhile, the total organic carbon (TOC) of TC (50 mL, 50 mg/L) achieved a removal rate (TOC/TOC0) of 50.28%. Zn@Co-N-C-1000/PMS maintained over 83.27% TC degradation after five cycles. The adsorption mechanism of the catalyst for TC was investigated through the analysis of adsorption kinetics and isotherm models. The quenching test and EPR results indicated that TC was primarily degraded through the nonradical pathway. The efficient degradation of TC is attributed to the rapid electron transfer processes occurring at the two-phase interface and the redox cycling of Co0/Co2+/Co3+. Finally, LC-MS was used to analyze the intermediate products of TC degradation in the Zn@Co-N-C-1000/PMS system, and two degradation pathways were proposed.

Increasing catalytic efficiency of cobalt centers in oxygen reduction reaction - Evidence from cobalt with salen ligands polymer complex

Substantial research is performed for cobalt-based catalysts for various applications in catalysis, including oxygen reduction reaction (ORR) catalysis in nonaqueous electrolytes. Cobalt exhibits high catalytic activity due to partially filled d-orbitals, which promote the formation of chemisorption bonds with various molecules. The catalytic activity of metal centers can be influenced both by changing their immediate environment and by varying the reaction conditions. This paper investigates the influence of solvent type, electrolyte concentration, and organic framework conductivity on the efficiency of ORR catalysis in non-aqueous electrolytes as illustrated by poly-CoSal polymer complex. The findings show that the increase in the solvent donor number of and conductivity of the organic backbone leads to highly efficient cobalt catalysts, which can be potentially be applied in oxygen cathodes of Li-O2 batteries. CoSal-based catalysts increase the discharge voltage of Li-O2 cells and can operate in dry atmospheric air.

Adsorption Property and Morphology Evolution of C Deposited on HCP Co Nanoparticles.

Despite extensive studies of deposited carbon in Fischer-Tropsch synthesis (FTS), an atomic-level comprehension of the effect of carbon on the morphology of cobalt-based FTS catalysts remains elusive. The adsorption configurations of carbon atoms on different crystal facets of hexagonal close-packed (hcp) Co nanoparticles were studied using density functional theory (DFT) calculations to explore the interaction mechanism between C and Co surfaces. The weaker adsorption strength of C atoms on Co(0001), Co(10-10), and Co(11-20) surfaces accounted for lower diffusion energy, leading to the facile formation of C dimers. Electronic property analysis shows that more electrons are transferred from Co surfaces to C atoms on corrugated facets than on flat facets. The deposition of carbon atoms on Co nanoparticles affects surface energy by forming strong Co-C bonds, which causes the system to reach a more energetically favorable morphology with an increased proportion of exposed Co(10-12) and Co(11-20) areas as the carbon content increases slightly. This transformation in morphology implies that C deposition plays a crucial role in determining the facet proportion and stability of exposed Co surfaces, contributing to the optimization of cobalt-based catalysts with improved performance.

The impact of support selection and Co loading amount on the catalytic performance for methane combustion

Methane (CH4) is a key component of natural gas and is essential for energy production and utilization. However, due to its strong greenhouse effect, efficient catalytic combustion methods are needed to convert it into CO2 and H2O. This study systematically evaluates the catalytic performance of Co, CoO, and Co3O4 in methane catalytic combustion, particularly highlighting the superior activity of Co3O4. To improve catalytic efficiency, this paper examines the effects of SiO2, Al2O3, and CeO2 as support materials using co-precipitation and impregnation methods. The results show a significant improvement in the catalytic activity of Co3O4 supported on CeO2, attributed to CeO2's unique redox properties and high oxygen storage capacity. Additionally, the study explores the impact of different loading amounts (5%, 10%, 15%, 20%) of Co3O4(x)-CeO2 catalysts on their performance. The optimal 10%wt Co3O4–CeO2 catalyst achieves methane conversion rates of 10%, 50%, and 90% at temperatures of 376 °C, 473 °C, and 578 °C, respectively, demonstrating exceptional stability during a 20-h stability test and the ability to adapt to fluctuations in CH4 concentrations in low-oxygen environments, while also exhibiting significant catalytic activity across a range of methane concentrations from 0.5% to 2.5%. These findings provide important theoretical and experimental guidance for the application of cobalt-based catalysts in CH4 combustion, paving the way for future catalyst design and optimization.

Exploring the potential of cobalt-based catalysts in the methane dry reforming for sustainable energy applications

Cobalt-based powder catalysts with different Co loadings were synthesized via wet impregnation using MgAl2O4 spinel as support. The catalytic properties of the solids were evaluated in the dry-reforming methane at different reaction temperatures and two CH4:CO2 ratios. The catalyst with higher cobalt content (13 %) presented superior performance due to increased Co0 species availability, confirmed by XPS analysis. Besides, this catalyst displayed remarkable resistance to carbon deposition at 550 °C and CH4:CO2 1: 1 ratio. In-situ DRIFT measurements demonstrated the formation and transformation of carbonate and hydrogen carbonate species during the DRM reaction, highlighting efficient CO2 and CH4 activation on the catalyst surface. Based on this data, a structured catalyst was deposited on top of the FeCrAlloy monolith, which was active, stable, selective for H2, and resistant against on/off cycles. Compared with the powder catalyst, the structured system displayed higher catalytic activity, possibly due to higher reducibility of metal species and improved heat transfer provided by the FeCrAlloy substrate. The results highlight the potential of Co-based structured catalysts for H2 or synthesis gas production processes.

Promotion of Nb-Co3O4 chemical interfaces on N2 selectivity in selective catalytic oxidation of NH3 over cobalt-based catalysts

Co3O4 catalysts possess high activity in selective catalytic oxidation of NH3 (NH3-SCO), but the low N2 selectivity hinders their potential application. To enhance N2 selectivity, the chemical bonded Nb-O-Co catalyst by the deposition of Nb species onto Co3O4 (Nb/Co3O4-0.03) is constructed. It shows 100 % NH3 conversion and 82 % N2 selectivity at 180°C, and the N2 selectivity is 2.2-fold higher than that of Co3O4 (38 %). The failure of enhancement in N2 selectivity for physically mixed Co3O4 and NbOx (NbOx|Co3O4-0.03) further indicates the crucial role of chemical bonded Nb-O-Co in enhancing N2 selectivity. In situ diffuse reflectance infrared Fourier transform spectra and NH3 temperature-programmed desorption results show the formation of new NH3 adsorption sites. Importantly, intermediates NO- stabled on Nb/Co3O4-0.03 tends to react with -NH2 to produce N2 through internal selective catalytic reduction (iSCR). This work offers insights into enhancing the N2 selectivity in NH3-SCO and advances understanding of iSCR mechanism.

A highly efficient Co-based catalyst for peroxymonosulfate activation for rapid degradation of RhB over a wide pH range

Cobalt-based materials have been demonstrated to be effective heterogeneous catalysts for peroxymonosulfate activation in degrading many refractory organic pollutants. In this study, a new cobalt-based catalyst was prepared using cobalt chloride hexahydrate (CoCl2·6H2O) as the Co2+ source, 2,3-pyrazine dicarboxylic acid and 3,6-DI-4-pyridyl-1,2,4,5-tetrazine (4-PYTZ) as ligands. This catalyst was employed as a peroxymonosulfate activator for the degradation of Rhodamine B(RhB). The results indicated that the prepared Co-based catalyst can effectively degrade RhB dye in aqueous solution by activating peroxymonosulfate (PMS). Specifically, when the initial concentration of RhB was 20 mg/L, its degradation rate exceeded 98 % within merely 9 min. The factors influencing the activation of PMS by the Co-based catalyst were examined, including PMS concentration, reaction temperature, solution pH, and the concentration of organic pollutants. Stability and reusability tests demonstrated that the prepared catalyst exhibited good stability, with the degradation rate of RhB remaining above 97 % after four repetitive experiments. Free radical quenching experiments and electron paramagnetic resonance (EPR) analyses revealed that sulfate radicals (SO4−) and hydroxyl radicals (OH) are the primary reactive radicals accountable for the degradation process. Additionally, it displayed excellent adaptability over a wide pH range, particularly within the pH levels ranging from 5 to 9. This study demonstrates that the prepared Co-based catalyst can serve as a stable and effective option for degrading organic dyes in wastewater treatment applications.

Advanced electrochemical oxidation of EDTA-Ni via cobalt single-atom catalysts: Exploring indirect persulfate activation pathways

This study explores an innovative electrochemical strategy for the removal of the highly stable and toxic EDTA-Ni complex found in electroplating wastewater. Utilizing a cobalt-based single-atom catalyst (Co-NC) in an electro-enhanced system, we achieved significant activation of peroxydisulfate (PDS) for effective degradation of EDTA-Ni. Under optimal conditions of 40 mA current density and a pH range of 3–7, more than 97% of EDTA-Ni (1 mM) was successfully degraded within 90 min. Through detailed electrochemical experiments, we identified that atomic hydrogen (H*) played a crucial role in the indirect activation of PDS, facilitating the formation of reactive sulfate radicals (·SO4-). Computational analysis using density functional theory (DFT) confirmed that the H*-mediated reduction pathway had a notably low energy barrier (ΔGbs = 0.51 eV), making it the dominant activation mechanism. Gas chromatography-mass spectrometry (GC–MS) further revealed the primary degradation intermediates, providing insights into the breakdown process of EDTA-Ni. This research underscores the potential of Co-NC catalyst as a highly effective catalyst for treating persistent heavy metal complexes in advanced oxidation systems.

Ionic Liquid/Deep Eutectic Solvent-Mediated Calcining Synthesis of Cobalt-Based Electrocatalysts for Water Splitting.

The recent advancements of ionic liquids (ILs) and deep eutectic solvents (DESs) in the synthesis of cobalt-based catalysts for water splitting is reviewed. ILs and DESs possess unique physical and chemical properties, serving as solvents, templates, and reagents. Combined with calcination techniques, their advantages can be fully leveraged, enhancing the stability and activity of resulted catalysts. In these solvents, not only are they suitable for simple one-step calcination, but also applicable to more complex multi-step calcination, suitable for more complex reaction conditions. The designability of ILs and DESs allows them to participate in the reaction as reactants, providing metal and heteroatoms, simplifying the preparation system of cobalt phosphide, sulfide, and nitride. This work offers insights into design principles for electrocatalysts and practical guidance for the development of efficient and high-performance materials for hydrogen production and energy storage systems.