Carbon Catalyst Research Articles

Effect of Dual Heat Treatment on the Oxygen Reduction Performance of Nanoparticles of Pt on Carbon Catalysts Prepared by Continuous Flow Microwave Technology

Effect of Dual Heat Treatment on the Oxygen Reduction Performance of Nanoparticles of Pt on Carbon Catalysts Prepared by Continuous Flow Microwave Technology

Low-temperature activated porous carbon with functional groups derived from waste tea powder as a potential catalyst for CO2 fixation into cyclic carbonates

The globe is currently confronted with two main environmental problems: environmental solid waste and greenhouse gases. Thus, it is urgent to mitigate these issues and convert them into value-added products. In this context, this work demonstrated the mitigation of two global issues with a single approach. This work established a facile process for a hierarchical porous carbon from abundant bio-waste, such as waste tea powder, and employed it as a heterogeneous catalyst for CO2 fixation into cyclic carbonate. Derived porous carbon catalysts, WTC-1 (Waste tea carbon), WTC-2, AWTC-2-400 (Activated waste tea carbon), AWTC-2a-400, AWTC-2-600, and AWTC-2-800, were produced without the use of solvent by acid-free washing and KOH-free activation. These WTC catalysts were characterized by several standard techniques: XRD, FTIR, XPS, SEM, BET, and TPD. Among the low-temperature activated carbon catalysts, AWTC-2a-400 with potassium-based salt, KI exhibited excellent conversion of propylene oxide (98 %) and ≥99 % selectivity of propylene carbonate without solvent under mild conditions of 2.5 MPa, 120 °C, and 2 h. It was observed that the catalytic activity of the WTC catalyst was attributed to the presence of Lewis acidic and basic sites, CaO/CaCO3, MgO, –COOH/OH, and –NH, which are capable of activating the CO2 molecule. Further, the developed catalytic system (AWTC-2a-400/KI) demonstrated superior catalyst versatility for various epoxides under optimized conditions. Moreover, AWTC-2a-400 showed good stability and reusability. Importantly, all reactions were conducted on a gram scale, and the proposed catalyst was effective, which might be favorable for future industrial applications.

Cu/Co Bimetallic Carbon Catalyst as a Highly Efficient Promoter for Reactive Dyes Degradation with PMS.

The synergistic effect between bimetallic catalysts has been confirmed as an effective method for activating persulfate (PMS). Therefore, we immobilized copper-cobalt on chitosan to prepare bimetallic carbon catalysts for PMS activation and degradation of reactive dyes. Experimental results demonstrate that the CuCo-CTs/PMS catalytic degradation system exhibits excellent degradation performance toward various types of reactive dyes (e.g., Ethyl violet, Chlortalidone, and Di chlorotriazine), with degradation rates reaching 90% within 30 min. CuCo-CTs exhibit high catalytic activity over a wide pH range of 3-11 at room temperature and under static conditions, degrading over 92% of RV5 within 60 min. ultraviolet-visible (UV-vis) spectroscopy and color changes in the dye solution confirm the effective degradation of RV5, with a degradation rate of 97.2% within 10 min. Additionally, CuCo-CTs demonstrate good stability and reusability, maintaining a degradation rate of 92.8% after eight cycles. Kinetic studies indicate that the degradation follows pseudo-first-order kinetics. Furthermore, based on the results of radical scavenging experiments, the catalytic degradation mechanism of the dye involves both radical and nonradical pathways, with 1O2 identified as the primary active species. This study provides insights and experimental evidence for the application of persulfate oxidation in the treatment of dyeing wastewater.

Effects of porous structure and oxygen functionalities on electrochemical synthesis of hydrogen peroxide on ordered mesoporous carbon

Two-electron oxygen reduction reaction (2e− ORR) is a promising alternative to energy-intensive anthraquinone process for hydrogen peroxide (H2O2) production. Metal-free nanocarbon materials have garnered intensive attention as highly prospective electrocatalysts for H2O2 production, and an in-depth understanding of their porous structure and active sites have become a critical scientific challenge. The present research investigates a range of porous carbon catalysts, including non-porous, microporous, and mesoporous structures, to elucidate the impacts of porous structures on 2e− ORR activity. The results highlighted the superiority of mesoporous carbon over other porous materials, demonstrating remarkable H2O2 selectivity. Furthermore, integration of X-ray photoelectron spectroscopy (XPS) data analysis with electrochemical assessment results unravels the moderate surface oxygen content is the key to increase 2e− ORR activity. These results not only highlight the intricate interplay between pore structure and oxygen content in determining catalytic selectivity, but also enable the design of carbon catalysts for specific electrochemical reactions.

Efficient Catalytic Elimination of Toxic Volatile Organic Compounds via Advanced Oxidation Process Wet Scrubbing with Bifunctional Cobalt Sulfide/Activated Carbon Catalysts.

Advanced oxidation process (AOP) wet scrubber is a powerful and clean technology for organic pollutant treatment but still presents great challenges in removing the highly toxic and hydrophobic volatile organic compounds (VOCs). Herein, we elaborately designed a bifunctional cobalt sulfide (CoS2)/activated carbon (AC) catalyst to activate peroxymonosulfate (PMS) for efficient toxic VOC removal in an AOP wet scrubber. By combining the excellent VOC adsorption capacity of AC with the highly efficient PMS activation activity of CoS2, CoS2/AC can rapidly capture VOCs from the gas phase to proceed with the SO4•- and HO• radical-induced oxidation reaction. More than 90% of aromatic VOCs were removed over a wide pH range (3-11) with low Co ion leaching (0.19 mg/L). The electron-rich sulfur vacancies and low-valence Co species were the main active sites for PMS activation. SO4•- was mainly responsible for the initial oxidation of VOCs, while HO• and O2 acted in the subsequent ring-opening and mineralization processes of intermediates. No gaseous intermediates from VOC oxidation were detected, and the highly toxic liquid intermediates like benzene were also greatly decreased, thus effectively reducing the health toxicity associated with byproduct emissions. This work provided a comprehensive understanding of the deep oxidation of VOCs via AOP wet scrubber, significantly accelerating its application in environmental remediation.

Advances in electrocatalytic carbon dioxide reduction reactors, electrolytes and catalysts

With the advance of The Times, people's demand for fossil energy has greatly increased, and it is the main energy for people to develop economy and science and technology. However, the large-scale exploitation of fossil energy has led to environmental pollution and energy crisis, and the concentration of CO2 in the air continues to rise, and the greenhouse effect is becoming more and more serious. Therefore, the conversion of CO2 into the high value-added fuels and chemicals we need will be a major measure to solve environmental problems. So, converting CO2 into fuels or high value-added chemicals using CO2 electrocatalytic reduction (CO2RR) technology is an effective way to alleviate the current problems of energy and environment. In this paper, we summarize the research progress in reaction systems, electrolyte effects, and catalyst development in CO2RR experiments, focusing on the electrocatalytic aspects of CO2. Finally, we provide an outlook on the CO2 electrocatalysis industry.

MIL-101(Fe)-derivatized cathode as an efficient oxygen electrocatalyst for rechargeable Zn-air battery

The exploration of multifunctional electrocatalysts with cost-effective and high kinetic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the development of advanced energy conversion and storage equipment. Herein, a novel hierarchical mesoporous/macropores MIL-101(Fe) derivative carbon catalyst material was prepared by a simple molten ZnCl2-assisted synthesis route. Specifically, 1H-benzotriazole (BTA) organic ligands were intentionally introduced as nitrogen sources in order to induce the formation of charge-rich regions through an electronegative nitrogen doping control strategy, and most importantly, the lone pair electron-rich nature of element N could facilitate the separation and anchoring of iron species enchanted the utilization rate of active sites. Because of these properties, the as-prepared catalyst (denoted as FeSACs/NxC) possesses unrivalled bifunction electrocatalytic activity and durability for the ORR and OER. The FeSACs/N1.25C as working electrode exhibits a quite satisfactory electrochemical performance for the ORR (half-wave potential of 0.82 V) and OER (a small overpotential of 302 mV at 10 mA cm−2) in the classic three-electrode configuration. Moreover, the FeSACs/N1.25C-based air cathode imparts encouraging performance in a rechargeable Zn–air battery prototype with an open-circuit voltage of 1.45 V, a specific capacity of 792.16 mAh g−1, an energy density of 871.38 Wh kg−1, and excellent stability for 120 h. This work has opened the way for the development of low-cost, fast kinetic and stable non-noble metal multifunctional catalysts.

Oxygen vacancy-induced nonradical degradation of nitroso-containing organics in Fe3O4@N[sbnd]C electro-Fenton reaction at a wide pH range

In this work, Fe3O4-anchored nitrogen-doped carbon catalyst (Fe3O4@N–C) with abundant oxygen vacancies (Vo) and mesoporous structure was successfully synthesized for electro-Fenton (EF) catalytic process. The catalyst demonstrated impressive degradation efficiency towards nitroso-containing organics due to the superior electronic transfer of N–C skeleton and Vo, making it easier for the electron-deficient –NO2 groups to adsorb on the catalyst surface and oxidize rapidly. Typically, the degradation efficiency of p-nitrophenol (PNP) reached 95.6 % in natural pH. Notably, the catalyst exhibited excellent performance over a wide pH range (3 ∼ 11), and has strong anti-interference performance against anions and natural organic matter in water matrix. Mechanism analysis indicated that Vo could promote the formation of highly active electron-rich Fe(II) species, and promote the activation of H2O2 and O2 as additional active sites, thus, a large amount of ·OH and O2·- would be produced and then quickly converted into 1O2. As a result, 1O2 is the main reactive species for PNP degradation in Fe3O4@N–C electro-Fenton reaction. The results will provide insights into the design of high-performance catalysts for the selective oxidation of organic pollutants in wastewater.

Electrochemical Properties of NiCo2O4/WO3/Activated Carbon Wheat Husk Nano-Electrocatalyst for Methanol and Ethanol Oxidation

It is common to use efficient catalysts in the anodes and cathodes of methanol and ethanol fuel cells, such as platinum and ruthenium. However, due to their expansivity and rarity, finding a suitable alternative is important. In this work, multi-component catalysts consisting of tungsten oxide, nickel cobaltite, and activated carbon were synthesized through the hydrothermal method. The performance of catalysts in the processes of methanol and ethanol oxidation reactions (MOR and EOR) were investigated. The addition of activated carbon obtained from wheat husk, with an excellent active surface and acceptable electrical conductivity, to the matrix of the catalyst significantly facilitated the oxidation process of alcohols and enhanced the efficiency of the catalyst. The physical and electrochemical characterization of the NiCo2O4/WO3 hybridized with the wheat husk-derived activated carbon (ACWH) catalyst indicated its successful synthesis and good performance in the alcohol oxidation process. NiCo2O4/WO3/ACWH with an oxidation current density of 63.39 mA/cm2 at the peak potential of 0.58 V (1.59 vs. RHE), a cyclic stability of 98.6% in the methanol oxidation reaction (MOR) and 27.98 mA/cm2 at the peak potential of 0.67 V (1.68 vs. RHE), and a cyclic stability of 95.7% in the ethanol oxidation reaction (EOR) process can be an interesting option for application in the anodes of alcohol fuel cells.

NC Loaded PtM Alloy from M-NC with Ultralow Pt Loading for Oxygen Reduction Reaction

Developing low Pt or non-precious metal catalysts for oxygen reduction reaction (ORR) has becoming necessary in recent years. Herein, PtM alloy anchored on nitrogen-doped carbon (PtM/NC, M=Fe, Co) catalyst with ultralow Pt loading (∼1 wt%) is prepared from the simple two-process pyrolysis, namely from C to M-NC then to PtM/NC. The as-prepared PtM/NC (M=Fe, Co) shows an excellent ORR catalytic performance with the peak potential and half-wave potential of 0.901 and 0.870 V for PtFe/NC, 0.868 and 0.845 V for Pt3Co/NC. The ORR on PtM/NC (M=Fe, Co) is a mainly direct 4-electron reaction pathway (3.75–3.90) in alkaline solution. Moreover, they possess good methanol tolerance and stability. Synergistic effect of Pt and M together with N species result in the excellent ORR catalytic activity of PtM/NC (M=Fe, Co). The negative shift of Pt binding energy caused by both lattice contraction and electron orbital coupling from M is beneficial for reducing the d-band center of Pt, weakening the oxygen binding energy and enhancing the ORR intrinsic activity of Pt. The strong interactions between NC and PtM alloy are beneficial for anchoring PtM nanoparticles, promoting the stability of catalyst. This work provides a new strategy for preparing ultralow Pt loading catalysts.

Cu-optimized long-range interaction between Co nanoparticles and Co single atoms: Improved Fenton-like reaction activity

The interplay between multi-atom assembly configurations and single atoms (SAs) has been gaining attention in research. However, the effect of long-term range interactions between SAs and multi-atom assemblies on the orbital filling characteristics has yet to be investigated. In this context, we introduced copper (Cu) doping to strengthen the interaction between cobalt (Co) nanoparticles (NPs) and Co SAs by promoting the spontaneous formation of Co–Cu alloy NPs that tends toward aggregation owing to its negative cohesive energy (−0.06454), instead of forming Cu SAs. The incorporation of Cu within the Co–Cu alloy NPs, compared to the pure Co NPs, significantly expedites the kinetics of peroxymonosulfate (PMS) oxidation processes on Co SAs. Unlike Co NPs, Co–Cu NPs facilitate electron rearrangement in the d orbitals (especially dz2 and dxz) near the Fermi level in Co SAs, thereby optimizing the dz2–O (PMS) and dxz–O (SO5−) orbital interaction. Eventually, the Co–Cu alloy NPs embedded in nitrogen-doped carbon (CC@CNC) catalysts rapidly eliminated 80.67% of 20 mg L−1 carbamazepine (CBZ) within 5 min. This performance significantly surpasses that of catalysts consisting solely of Co NPs in a similar matrix (C@CNC), which achieved a 58.99% reduction in 5 min. The quasi in situ characterization suggested that PMS acts as an electron donor and will transfer electrons to Co SAs, generating 1O2 for contaminant abatement. This study offers valuable insights into the mechanisms by which composite active sites formed through multi-atom assembly interact at the atomic orbital level to achieve high-efficiency PMS-based advanced oxidation processes at the atomic orbital level.

Influence of a carbon support on the catalytic activity and durability of the Pt-based electrocatalysts

There are numerous carbon materials that are deemed promising for use as supports in electrocatalysts for PEMFCs. We have carried out a comparative analysis of compositional, morphological and electrochemical characteristics of the platinum–carbon catalysts synthesized by a single method on various carbon supports (Vulcan XC-72, Ketjenblack EC-300 J, Ketjenblack EC-600JD and N-doped Ketjenblack EC-600JD) and the commercial electrocatalyst.The Pt/C materials obtained on highly dispersed supports (from 800 m2 g−1) exhibit almost 1.5times greater ORR activity compared to those with a specific surface area of less than 250 m2 g−1. Doping of a highly dispersed support with nitrogen leads to a 30 % increase in the durability of the catalysts based thereon. The resulting Pt/C on the N-doped support exhibits an ESA of more than 110 m2 g−1 and an ORR mass activity of about 430Ag-1Pt, which correspond to the DOE targets and are 1.6and 1.7times higher than those of the commercial analog.

Highly Curved Defect Sites: How Curvature Effect Influences Metal-Free Defective Carbon Electrocatalysts.

Topological defects are widely recognized as effective active sites toward a variety of electrochemical reactions. However, the role of defect curvature is still not fully understood. Herein, carbon nanomaterials with rich topological defect sites of tunable curvature is reported. The curved defective surface is realized by controlling the high-temperature pyrolytic shrinkage process of precursors. Theoretical calculations demonstrate bending the defect sites can change the local electronic structure, promote the charge transfer to key intermediates, and lower the energy barrier for oxygen reduction reaction (ORR). Experimental results convince structural superiority of highly-curved defective sites, with a high kinetic current density of 22.5mAcm-2 at 0.8V versus RHE for high-curvature defective carbon (HCDC), ≈18 times that of low-curvature defective carbon (LCDC). Further raising the defect densities in HCDC leads to the dual-regulated products (HCHDC), which exhibit exceptionally outstanding ORR activity in both alkaline and acidic media (half-wave potentials: 0.88 and 0.74V), outperforming most of the reported metal-free carbon catalysts. This work uncovers the curvature-activity relationship in carbon defect for ORR and provides new guidance to design advanced catalysts via curvature-engineering.

Transition-Metal Porphyrin-Based MOFs In Situ-Derived Hybrid Catalysts for Electrocatalytic CO2 Reduction.

Excellent electrocatalytic CO2 reduction reaction activity has been demonstrated by transition metals and nitrogen-codoped carbon (M-N-C) catalysts, especially for transition-metal porphyrin (MTPP)-based catalysts. In this work, we propose to use one-step low-temperature pyrolysis of the isostructural MTPP-based metal-organic frameworks (MOFs) and electrochemical in situ reduction strategies to obtain a series of hybrid catalysts of Co nanoparticles (Co NPs) and MTPP, named Co NPs/MTPP (M = Fe, Co, and Ni). The in situ introduction of Co NPs can efficiently enhance the electrocatalytic ability of MTPP (M = Fe, Co, and Ni) to convert CO2 to CO, particularly for FeTPP. Co NPs/FeTPP endowed a high CO faradaic efficiency (FECOmax = 95.5%) in the H cell, and the FECO > 90.0% is in the broad potential range of -0.72 to -1.22 VRHE. In addition, the Co NPs/FeTPP achieved 145.4 mA cm-2 at a lower potential of -0.70 VRHE with an FECO of 94.7%, and the CO partial currents increased quickly to reach 202.2 mA cm-2 at -0.80 VRHE with an FECO of 91.6% in the flow cell. It is confirmed that Co NPs are necessary for hybrid catalysts to get superior electrocatalytic activity; Co NPs also can accelerate H2O dissociation and boost the proton supply capacity to hasten the proton-coupled electron-transfer process, effectively adjusting the adsorption strength of the reaction intermediates.

Manufacturing the activated carbon catalyst of impregnated palm core shells for biodiesel production

This research aims to produce activated carbon-based heterogeneous catalyst derived from palm kernel shells impregnated with a KOH solution and to determine the effects of the concentration of the KOH solution and the time period during impregnation. The variables observed included KOH concentration and impregnation time. The impregnation process used KOH solution with the solution concentrations of 1N, 2N, 3N, 4N and 5N with impregnation process within 18 hours, 21 hours and 24 hours. AAS, FTIR and SEM were analyzed after impregnation with different concentrations and times. The results of the analysis of potassium metal showed the highest absorption occurred at a concentration of 5N within 21 hours at 25.4570%. The application of the activated carbon catalyst from palm kernel shells was conducted in making biodiesel. The process of making biodiesel was carried out with a reaction time of 120 minutes at a temperature of 60℃ with a molar ratio of 1: 12 using a catalyst of 2% (% w/w). Biodiesel yield testing referred to SNI 04-7182-2015. The analysis results obtained showed 879 kg/m3 density, 6.1 cst viscosity, 0.5 acid number, and 174℃ flash point.

Continuous kinetics of 2-hydroxyisobutryic acid esterification using solid acid granular and monolithic activated carbon catalysts

Kinetics of 2-hydroxyisobutyric acid (2-HIBA) esterification with ethanol was studied using sulfonated carbon catalysts in granular (sGAC) and monolith (sACM) forms in a continuous flow packed bed reactor. 2-HIBA is a potential biobased carboxylic acid and its ester a sustainably produced industrial solvent. The catalyst monolith form, made from renewable carbon, offers significantly higher space time yields and conversions, yet little kinetic data or models are available for its use, especially under non-ideal conditions. The effect of ethanol/2-HIBA molar ratio (44, 10, 3.6 and 1.5) at different liquid residence times (3–9 min) was investigated using sGAC. Kinetics of sACM esterifications were investigated at a molar ratio of 3.6 by varying the residence time (2–7 min) and compared with the sGAC. The sACM displayed higher ester yields, acid conversions, and significantly higher reaction rates and space–time-yields (2.1–2.8 ×) compared to the sGAC due to higher surface area to volume ratio. The sACM reaction rates and turnover frequency were comparable to solid acid resins and sulfated silica and zirconia. Pseudo-homogeneous, Eley-Rideal and Langmuir-Hinshelwood models were applied to fit the kinetic data, and the reaction system parameters were obtained through regression analysis. The LH dual active site model resulted in the lowest mean relative error for both 2-HIBA and ester concentration residuals. Adsorption/desorption equilibrium constants for 2-HIBA, ethanol, and ester, were higher compared to water suggesting hydrophobic regions in the sGAC/sACM. Estimation of the external and internal mass transfer criteria indicated negligible effects of mass transfer. With further development sACM and the kinetic model can be used for reactor design of continuous esterification processes using solid acid monolith catalysts.

Study on H3PO4-activated carbon catalytic co-pyrolysis of bamboo and LDPE to poly-generation syngas and aromatics at low temperature

Biomass-derived carbon activated by H3PO4 was adopted to catalytic co-pyrolysis of bamboo and low-density polyethylene (LDPE) to produce syngas and aromatics on a fixed bed reactor. Effects of LDPE ratio in the feedstock, catalytic co-pyrolysis temperature and ratio of catalyst to feedstock on the yields and compositions of the products were investigated. The increase of LDPE ratio in liquid first improved and then reduced the relative content of aromatics, while it showed a positive effect on the yield and the H2/CO ratio of gas. 500℃ was an optimum temperature, under which the relative content of aromatics in liquid kept higher, meanwhile, avoided the undesirable polymerization reactions of monocyclic aromatics. At the same time, the content of H2 in gas reached a maximum (59.3%), which was in favor of poly-generation. H3PO4-activated carbon catalyst (H3PO4-ACC) with abundant functional groups on surface catalyzed cracking, hydrodeoxygenation, cyclization and aromatization reactions so as to facilitate the generation of aromatics. Non-condensable gas was dry reformed on P-ACC at the expense of CO2, CH4 and CO to generate char and H2. When the reaction condition was at a LDPE ratio of 50%, a catalyst/feedstock ratio of 2:1 and at 500℃, the relative content of aromatics in liqiud was 81.65% and the proportion of syngas component in gas was 79.73%. The volume ratio of H2/CO approached to 3:1 in gas under this condition. H3PO4-ACC catalytic co-pyrolysis of bamboo and LDPE could obtain high quality gas and liquid products at a relative low reaction temperature, which provided a new research idea on high-value application of biomass and waste plastics.

Fast degradation of vinyl chloride by green rust and nitrogen-doped graphene

Carbonaceous materials catalyze reductive dechlorination of chlorinated ethylenes (CEs) by iron(II) materials providing a new approach for the remediation of CE polluted groundwater. While most CEs are reduced via β-elimination, vinyl chloride (VC), the most toxic and recalcitrant CE, degrades by hydrogenolysis. The significance of carbon catalysts for reduction of VC is well documented for iron(0) systems, but hardly investigated with iron(II) materials as reductants. In this study, a layered iron(II)‑iron(III) hydroxide sulfate (green rust) was used as reductant for VC, with an N-doped graphene (NG), prepared by co-pyrolysis of graphene and urea, as catalyst. VC (80 μM) was completely reduced to ethylene within 336 h in the presence of 5 g Fe/L GR and 5 g/L NG pyrolyzed at 950 °C, following pseudo-first-order kinetics with a rate constant of 0.017 h−1. Dosing experiments demonstrated that dechlorination of VC takes place on the NG phase. Monitoring of hydrogen formation, cyclic voltammetry, and quenching experiments demonstrated that atomic hydrogen contributes significantly to the dehalogenation reaction, where NG is critical for formation of atomic hydrogen. CE competition experiments demonstrated the presence of specific VC reduction sites with hydrogenolysis being unaffected by concurrent β-elimination reactions. The system exhibited excellent performance in natural groundwaters and in comparison with iron(0) systems. This study demonstrates that GR + NG is a promising system for remediation of VC contaminated groundwater, and the mechanistic part of the study can be used as a reference for subsequent studies.

Insights on the activity-selectivity trade-off in iron-containing nitrogen-doped carbon catalyst via cobalt addition for oxygen reduction reaction in alkaline medium

Iron-based noble-metal-free electrocatalysts exhibit impressive performance and stability for the Oxygen reduction reaction (ORR) in alkaline media, but face challenges. This study investigates the impact of Co addition to Fe in nitrogen(N)-doped carbon (Fe/NC) catalysts prepared via one-pot synthesis involving direct pyrolysis of the metal (M) and 2,4,6-tris(2-pyridyl)-s-triazine complexes (M-TPTZ) on carbon. Comprehensive characterization reveals N-doped carbon structures with single-atom sites and metal oxides, with M-Nx centers mainly in carbon pores and metal oxides on the carbon surface. N2 adsorption/desorption experiments and electrochemical surface area (ECSA) reveals that Co introduction enhances the catalyst surface area. Moreover, Co addition alters nitrogenated species distribution, affecting catalytic activity. Electrochemical studies rank catalytic activity as Fe/NC < Co/NC < CoFe/NC, while rotating ring-disk electrode (RRDE) investigations show mixed 2 and 4 electrons pathways. Fe/NC follows a 4e- pathway with minimal HO2− production, while Co-containing catalysts suggest a mixed (2e- + 2e-) pathway with an average of 3.75 electrons involved. This divergence highlights nuanced electrochemical characteristics of Fe- and Co-based materials, emphasizing the need for in-depth characterization.

Efficient Atomically Dispersed Co/N-C Catalysts for Formic Acid Dehydrogenation and Transfer Hydrodeoxygenation of Vanillin.

Atomically dispersed catalysts have gained considerable attention due to their unique properties and high efficiency in various catalytic reactions. Herein, a series of Co/N-doped carbon (N-C) catalysts was prepared using a metal-lignin coordination strategy and employed in formic acid dehydrogenation (FAD) and hydrodeoxygenation (HDO) of vanillin. The atomically dispersed Co/N-C catalysts showed outstanding activity, acid resistance, and long-term stability in FAD. The improved activity and stability may be attributed to the high dispersion of Co species, increased surface area, and strong Co-N interactions. XPS and XAS characterization revealed the formation of Co-N3 centers, which are assumed to be the active sites. In addition, DFT calculations demonstrated that the adsorption of formic acid on single-atom Co was stronger than that on Co13 clusters, which may explain the high catalytic activity. The Co/N-C catalyst also showed promising performance in the transfer HDO of vanillin with formic acid, without any external additional molecular H2.