Porous Carbon Catalyst Research Articles

Salt template-assisted polymer tethering strategy to achieve high dispersed cobalt single atoms/clusters on porous carbon catalysts for effective Fenton-like reactions

The exploration of the synthesis of porous carbon-supported metal nanocatalysts with high metal loading and dispersion for the development of heterogenous catalysts is important. However, this remains a challenging subject. In this paper, a salt template-assisted polymer tethering strategy was proposed to prepare Co single atom and ultrafine cluster anchored on porous carbon (Co-NPC) with a high-loading of 16.9wt%, thereby exposing high density of reaction sites. The obtained Co-NPC catalyst exhibited excellent catalytic performance for almost 100% degradation of bisphenol A (BPA) within 20min, which is much faster than the CoSA-NPC catalyst with only single atom sites and Co-NC without salt template added. Radical quenching experiments and electron paramagnetic resonance tests verified that both the nonradical oxidation pathway by 1O2, the electron transfer and radical oxidation pathway by •OH, SO4•- appeared during the degradation process. After 3 cycles, the removal rate of BPA did not decrease significantly. The fixed bed experiment revealed that Co-NPC could realize the continuous degradation of methylene blue (MB) with almost 100% degradation efficiency. This research indicated that the strategy by pyrolyzing metal coordinated polymer is a potential method for the synthesis of high metal loading catalyst at gram scale, meeting the requirement of practical applications.

Highly stable and electron-rich Ni single atom catalyst for directed electroreduction of CO2 to CO

Transition metal-nitrogen-carbon (M−N−C) are considered as promising candidates for the electrochemical conversion of inert CO2 into high value-added CO products. However, previous reports have focused on Ni single-atom sites (Ni SAs) and the role of Ni nanoparticles (Ni NPs) in CO2 electroreduction reaction (CO2RR) has been overlooked. Herein, we prepared a series of Ni, N-codoped porous carbon (NiNC-T, T represents the temperature) catalysts by combining Ni phthalocyanine pyrolysis and acid etching strategy, which either contain only Ni SAs or both Ni SAs and Ni NPs. Notably, the NiNC-1100 catalyst with both Ni SAs and Ni NPs exhibited 99 % CO faradaic efficiency (FECO) at −0.66 V versus reversible hydrogen electrode (vs. RHE) and FECO above 98 % over a wide potential range (−0.66 V ∼ −1.06 V). Moreover, the FECO of NiNC-1100 remained above 95 % after 100 h of continuous electrocatalysis, which was significantly superior to that of the most advanced Ni single atom electrocatalysts. The systematic characterization results showed that the introduction of Ni NPs can promote the adsorption and activation of CO2 by increasing the electron cloud density of Ni SAs, thus enhancing the CO2RR catalytic performance.

S-N co-doped porous carbon as metal-free ORR electrocatalysts in zinc-air batteries

The implementation of zinc-air batteries (ZABs) requires the creation of economically feasible electrocatalysts for the oxygen reduction reaction (ORR) process. In this work, sulfur-nitrogen co-doped porous carbon materials (S-N-PC) were synthesized using a straightforward approach including ball milling followed by calcination without solvent. The optimized S-N-PC 1000 demonstrates exceptional ORR performance in 0.1 M KOH, with a half-wave potential of 0.870 V that outperforms commercial Pt/C. Furthermore, it exhibits remarkable durability and exceptional methanol resistance. The S-N-PC 1000 performs excellent performance as an air cathode in ZABs, exhibiting a peak power density of 159.26 mW cm−2 and outstanding stability for up to 720 h. Additionally, the energy efficiency decreases by only 2.52 % after undergoing more than 2000 cycles of charging and discharging at 5 mA cm−2. This study offers a novel concept for the development of eco-friendly porous carbon catalysts for ZABs.

Boosting Suzuki coupling reaction via pore expanding and palladium–zinc alloying

A palladium–zinc alloy nanoparticles decorated nitrogen-doped porous carbon catalyst (PdZn30–NC) was synthesized and utilized for Suzuki coupling reaction. The alloying palladium (Pd) with zinc (Zn) and pore expanding are realized simultaneously. Density functional theory (DFT) calculations and experimental studies reveal that the alloying Pd with Zn can lower the energy barrier in Suzuki coupling reaction. Nitrogen adsorption–desorption measurements uncover that pore expansion caused by the zinc nitrate hexahydrate assisted calcination gives rise to the multiplication of mesopore with a pore diameter of 6 nm, which facilitates mass transfer during the reaction. As a result, the alloying Pd with Zn and pore expanding together endow PdZn30–NC with excellent catalytic activity. PdZn30–NC demonstrates exceptional catalytic activity and stability in Suzuki coupling reaction. A high biphenyl yield of 97.7 % within 40 min and stable reusability of 93.3 % yield after five reuse cycles can be achieved. This work not only offers a viable method for Suzuki coupling reaction, but also provides insights for designing new catalysts toward Suzuki coupling reaction.

Enhanced CO2 conversion through confinement of cross-linked ionic polymer within the pores of porous carbon materials

It is crucial to employ an integrated catalyst to avoid the complications of the recovery process. This work reports the fabrication of porous carbon@ionic liquid (PC@IL) composites with readily accessible active ion sites, achieved by confining cross-linked ionic liquid (IL) within the channels of porous carbon (PC). The incorporation of porous carbon not only confines the IL within its framework, creating microsites for CO2 adsorption and conversion, but also simplifies catalyst recovery. The results indicate that PC@IL composites exhibit excellent cycloaddition activity towards CO2 in a co-catalyst- and solvent-free environment. Notably, PC@IL(C)-24 demonstrates remarkable catalytic performance across various epoxides under 1 bar of CO2, with yields above 90 % at 90 °C for 12 h, and achieving a remarkable styrene carbonate yield of up to 92.8 % under a CO2 pressure of 1 bar (at 100 °C for 12 h). Control experiments confirm that the confinement effect exerted by N,S co-doped carbon on cross-linked IL plays a pivotal role in enhancing both stability and activity of PC@IL composites, thereby providing novel insights for designing functionalized porous carbon catalysts for CO2 cycloaddition conversion.

Synthesis of nitrogen-rich porous carbon via a molecular confinement strategy for activating peroxymonosulfate in bisphenol A degradation: Role of singlet oxygen and electron transfer process

Nitrogen-doped porous carbon (NPC) catalysts show potential for activating peroxymonosulfate (PMS) to treat water pollution. However, nitrogen (N) experiences significant loss during pyrolysis, posing challenges for synthesizing N-rich carbon catalysts. This study innovatively proposed a molecular confinement strategy using the C−S−C bond formed between graphitic carbon nitride and mercaptan. Under this confinement, we successfully synthesized NPC-15 with a high N content (21.4 at%), surpassing most catalysts reported in the literature. NPC-15/PMS system showed excellent performance in degrading bisphenol A (BPA), achieving complete degradation within 3 min (kobs = 1.771 min−1), surpassing the effectiveness of most previously reported catalysts. The NPC-15/PMS system exhibited excellent performance and stability under various conditions, reducing BPA toxicity to ecological and human embryonic kidney cells. Moreover, it maintained stability during long-term continuous operation in a fixed-bed reactor, showing promise for practical applications. Through experiments and theoretical calculations, the mechanism of NPC-15 activating PMS was comprehensively investigated. The NPC/PMS system operated via a dual non-radical pathway involving singlet oxygen and electron transfer process induced by pyridinic N and graphitic N dual active sites. Pyridinic N promoted the generation of 1O2, while graphitic N supported the electron transfer process. This study introduced a new strategy for the preparation of N-rich carbon catalysts and proposed a novel method for the removal of emerging pollutants in water.

Impact of Exposed Crystal Facets on Oxygen Reduction Reaction Activity in Zeolitic Imidazole Frameworks

Oxygen reduction reactions (ORR) are critical reactions for efficient sustainable and renewable energy storage. However, the limitation of ORR is a slow kinetic reaction due to the multi-step transfer mechanism of electrons. Therefore, electrocatalysts with high ORR activity and stability are needed to overcome the reaction limitations. Zeolitic imidazole framework-67 (ZIF-67) has attracted attention in electrochemical applications due to its multiple redox-active sites and high stability in alkali conditions. The Co-doped porous carbon catalysts derived from ZIF-67 have the potential to be used as ORR catalysts with high performance, while pure phase ZIF-67 electrocatalyst for ORR is rarely studied. The work studies the importance of crystal facets on ORR reactivity. The results show that ZIF-67 nanocube exhibits excellent ORR activity with lower half wave-potential and faster kinetics process compared to its bulk structure. It is proposed that ZIF-67 nanocube provides improvement of selectivity for the four-electron pathway, which is a favorable process with higher reaction efficiency. The density functional theory (DFT) calculations suggest unsaturated Co2+ active sites with enriched (100) facets in the cubic crystal. Therefore, the fast diffusion of oxygen molecules to active sites and strong interaction with intermediate are observed in a cubic structure. The correspondence between experiment and calculation offers enhancement of ORR activity and selectivity from control-specific growth of (100) facet with cubic shape. The work introduces a new strategy for designing highly efficient ORR electrocatalysts with facet-controlled, allowing further study in other electrochemical reactions.

Facile and fast fabrication of CuCo alloy and N-codoped hierarchical porous carbon catalyst for efficient oxygen reduction reaction in microbial fuel cells

Designing a low-cost, high-performance oxygen reduction reaction (ORR) catalyst to replace the precious metal catalyst remains a huge challenge for microbial fuel cells (MFCs). Herein, a facile and rapid approach to fabricate highly active N-doped hierarchical porous carbon (NHPC) supported bimetal CuCo/NHPC composites with densely accessible active sites is developed by pyrolysis of Cu-doped ZIF-67 (CuCo-ZIF) precursor. In which, CuCo-ZIF precursor is synthesized through a one-pot hydrothermal method. Results showed that in addition to create additional Cu-Nx sites and increase N content, the Cu doping induces a hierarchical porous structure CuCo/NHPC composite with pores centered around 2.4, 4.2 nm and 10–60 nm, which can significantly accelerate the mass/electron transfer and improve efficient utilization of the active sites. The resulting CuCo/NHPC composite provides abundant active sites, high content of pyridinic-N and graphitic-N, which significantly boosts ORR performances. The CuCo/NHPC-T with pyrolysis temperature of 800 °C achieves remarkable ORR activity with low charge transfer resistances, high half-wave potential. The MFC assembled with CuCo/NHPC-800 (774.2 mW·m−2 and 0.713 V) significantly outperforms MFC assembled with Co-NC-800 (541.9 mW·m−2 and 0.583 V) in terms of maximum power density and open-circuit voltage. Moreover, the output voltage of MFC assembled with CuCo/NHPC-800 exhibited no significant downward trend within 30 days, which was better than that of Pt/C catalyst. This work provides a feasible time-saving route to develop promising nitrogen-enriched mesoporous carbon bimetallic ORR catalysts.

N/Se co-doped porous carbon catalyst derived from a deep eutectic solvent and chitosan as green precursors: Investigation of catalytic activity for metal-free oxidation of alcohols

Heteroatom-doped porous carbon-based materials with high surface area compared to their metal-based homologs are considered environmentally friendly and ideal catalysts for organic reactions. In this paper, a new method for the convenient fabrication, cost-effective, and high efficiency of nitrogen/selenium co-doped porous carbon-based catalysis (marked as N/SePC-T) was designed. The N/SePC-T catalysts were created from the direct pyrolysis of a eutectic solvent containing choline chloride/urea as the nitrogen-rich carbon source, selenium dioxide as a source of heteroatom and chitosan as a secondary carbon source in different temperatures (T). The efficacy of the carbonization temperature on the pore structure, morphology, and catalytic activity of the N/SePC-T materials was investigated and displayed, the N/SePC-900 (having a surface area of 562.01 m2/g and total pore volume of 0.2351 cm3 g−1) has the best performance. The morphology, structure, and physicochemical properties of N/SePC-900 were characterized using various analyses including XRD, TEM, TGA, FE-SEM, EDX, FT-IR, XPS, and Raman. The optimized N/SePC-900 catalyst indicated excellent catalytic performance in the oxidation of benzylalcohols to corresponding aldehydes in very mild conditions.

Enhancing Electrocatalytic Kinetics via Synergy of Co Nanoparticles and Co/Ni-N4-C- and N-Doped Porous Carbon.

Transition-metal species embedded in carbon have sparked intense interest in the fields of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, improvement of the electrocatalytic kinetics remains a challenge caused by the synergistic assembly. Here, we propose a biochemical strategy to fabricate the Co nanoparticles (NPs) and Co/Ni-N4-C co-embedded N-doped porous carbon (CoNPs&Co/Ni-N4-C@NC) catalysts via constructing the zeolitic imidazolate framework (ZIF)@yeast precursor. The rich amino groups provide the possibility for the anchorage of Co2+/Ni2+ ions as well as the construction of Co/Ni-ZIF@yeast through the yeast cell biomineralization effect. The functional design induces the formation of CoNPs and Co/Ni-N4-C sites in N-doped carbon as well as regulates the porosity for exposing such sites. Synergy of CoNPs, Co/Ni-N4-C, and porous N-doped carbon delivered excellent electrocatalytic kinetics (the ORR Tafel slope of 76.3 mV dec-1 and the OER Tafel slope of 80.4 mV dec-1) and a high voltage of 1.15 V at 10 mA cm-2 for the discharge process in zinc air batteries. It provides an effective strategy to fabricate high-performance catalysts.

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.

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.

Synergistic role of Co and CoP on highly dispersed cobalt nanoparticles embeded in porous carbon for efficient PH3 decomposition

Efficient resourceful treatment of phosphine tail gas is a huge challenge. In this study, a series of cobalt nanoparticles embeded in porous carbon (Co@C) catalysts were obtained via pyrolysis of Co-based MOF as precursor for catalytic decomposition of phosphine (PH3) by regulating the ratio of reactants of MOFs. The composition, morphology and structure of the catalysts were characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and BET measurement. The effect of Co@C catalysts with different reactant ratio on the catalytic decomposition of PH3 was tested, and the catalysts before and after the reaction were compared. It was found that the catalyst with MOF as the precursor after pyrolysis can still retain the porosity and large specific surface area of MOF. The metal cobalt nanoparticles and its oxides can be uniformly distributed in time under high loading, which is conducive to the reaction with phosphine to form metal phosphide (CoP), and the rapid and efficient decomposition of PH3 was completed under the synergistic effect of the two kinds of active sites of Co and CoP. The best catalytic decomposition efficiency is Co@C-5 catalyst, which can achieve 100 % decomposition efficiency at 350 °C and has good stability.

Efficient Electrosynthesis of Hydrogen Peroxide Using Oxygen-Doped Porous Carbon Catalysts at Industrial Current Densities.

Metal-free carbon catalysts (MFCCs) are one of the commonly used catalysts for electrocatalytic two-electron oxygen reduction (2e- ORR) synthesis of hydrogen peroxide (H2O2). Oxygen doping is an effective means to improve the performance of MFCCs, but the performance of oxygen-doped carbon catalysts is still not high enough, and the contribution of different oxygen functional groups (OFGs) to the catalytic performance is still inconclusive. In this paper, carbon-based catalysts with different oxygen contents and ratios of OFGs were prepared, and the high 2e- ORR activity of COOH + C-OH was demonstrated by combining the results of experiments and theoretical calculations. The prepared oxygen-doped carbon-based catalyst C-0.1M80 achieved an onset potential of 0.795 V (vs RHE), a selectivity of up to 98.2% (0.6 V vs RHE), and a H2O2 oxidation current of 1.33 mA cm-2 (0.5 V vs RHE) in a rotating ring-disk electrode test (0.1 M KOH solution), which was an outstanding performance in MFCCs. In a solid electrolyte flow cell, C-0.1M80 achieved a Faraday efficiency of 97.5% at 200 mA cm-2 with a corresponding H2O2 production rate of 123.7 mg cm-2 h-1. In addition, a flow cell stability test was performed at an industrial current density (100 mA cm-2) with an astounding 200 h of uninterrupted operation, also achieving an outstanding average Faradaic efficiency (95.8%).

Facile construction of a cobalt-incorporated N-doped porous carbon from biomass for highly efficient removal of tetracycline

The performance of heterogeneous carbon-based catalysts in advanced oxidation processes (AOPs) significantly relies on their structure and surface active sites. Herein, the cobalt-incorporated N-doped porous carbon (Co-NC) was successfully prepared from tannin by utilizing its strong ability to coordinate with metal ions. The characterization results revealed that Co-NC-900 possessed a porous structure with abundant mesopores, a relatively large BET surface area (187.16 m2/g), multivalent cobalt species (Co0, Co2+, Co3+) and optimal surface nitrogen sites. As a result, Co-NC-900 demonstrated efficient PMS activation, resulting in a 97.4% removal of tetracycline (TC), along with a rate constant (kobs) of 0.131 min−1 and TOC removal efficiency of 55.3% within 30 min. The analysis of radical inhibition and EPR results revealed that TC degradation was attributed to both non-radical (1O2) and radical (•OH and SO4•-) pathways. In addition, the outperformance of Co-NC-900 compared to Co-C-900 and NC-900 highlights the essential contributions of both Co and N in PMS activation. Mechanism studies have revealed that the presence of multivalent Co species promotes the Co-based redox cycle. This, in association with the enhanced electron transfer efficiency facilitated by N doping sites, accelerates the rapid generation of reactive oxygen species (ROSs). This work provides a straightforward strategy to fabricate transition metal-incorporated N-doped porous carbon catalysts from eco-friendly biomass, contributing to the effective treatment of organic contaminant.

Sustainable valorization of protein-rich tannery saline wastewater: Protein hydrolysate synthesis via protease and Fe3O4 porous carbon catalyst

The objective of the current study is to produce valuable protein hydrolysates (PHs) by fragmenting the proteins in protein-rich tannery wastewater (TANWWpro) through a protease-immobilized nanoporous carbon catalyst (PNPCC). The protease was isolated from the microorganism Lysinibacillus fusiformis MR1 and it contains 385 U/mL of proteolytic activity. For the immobilization of protease onto PNPCC, the ideal conditions were 2 h, pH 6–8, and 30–40 °C. FTIR, TGA, DSC, and XRD analyses were used to evaluate the protease immobilization on AGF-NPCC. For protein fragmentation, the appropriate pH, which was determined at 6, the ideal duration and temperature of 120 min at 30 °C as well as the required quantity of PNPCC were optimized. HPLC-free amino acid analysis has been used to validate the generation of PHs from TANWWpro, while electroanalytical methods including impedance spectroscopy and cyclic voltammetry have been used to establish their varied redox characteristics. Furthermore, PHs were extracted by using a Fe3O4- impregnated nanoporous carbon catalyst (Fe3O4-NPCC) and the SEM images verified the impregnation of Fe3O4 onto NPCC. Overall, employing the PNPCC and Fe3O4-NPCC, the generation and extraction of PHs from TANWWpro were both performed effectively.

Synergistic interaction of in situ S,N-codoping-mediated non-radical pathway for highly active and robust water decontamination

Metal-organic frameworks (MOFs)-derived heteroatom-doped carbon-based catalysts are commonly used in sewage treatment. However, the challenge lies in developing a simple route for heteroatom co-doping of MOFs-derived porous carbon that efficiently degrades organic pollutants without the need for additional post-treatment procedures. Herein, built-in Co nanoparticles are integrated with S,N-codoped porous carbon through a straightforward in situ co-doping strategy using ZnS nanoparticles as templates and a sulfur source. This approach simplifies the process of achieving S,N-codoping of zeolitic imidazolate frameworks-derived carbon without requiring extra nitrogen and sulfur sources or post-treatment procedures. The resulting Co@SNPC-900 catalyst demonstrates high catalytic performance in degrading tetracycline (TC) via peroxymonosulfate (PMS) activation, showing a removal efficiency of 97% in 30 min and excellent cycling stability. Furthermore, the Co@SNPC-900/PMS system shows strong resistance to changes in solution pH, interference from inorganic ions, and humic acid. The synergistic effects between S and N co-doping contribute to the formation of dominant non-radical pathways for boosting TC degradation. The study also elucidates three reaction pathways and identifies including sixteen intermediates with lower toxicity. This research presents a straightforward in situ co-doping strategy for producing highly active and durable built-in metal nanoparticles integrated porous carbon catalysts for environmental remediation.

Selective oxidation of cyclohexanol to cyclohexanone with peroxydisulfate over Co/N doped porous carbon

Cyclohexanone serves as a vital chemical intermediate in nylon production and as a solvent in the manufacturing of resins and paints. The quest for facile, environmentally-friendly, and cost-effective methods to achieve selective oxidation of cyclohexanol is highly desirable. In this study, we successfully achieved the oxidation in water solution using peroxydisulfate (PDS) activation. This was accomplished by employing a Co/N doped porous carbon catalyst synthesized through the one-step carbonization of zeolite-imidazolate frameworks (ZIFs). The catalysts derived from ZIFs with various Co/Zn ratios were extensively characterized using XRD, SEM, TEM, N2 adsorption–desorption, and XPS techniques. The catalyst's performance was assessed under different reaction conditions, including reaction temperature, PDS dosage, and water quality. Notably, the results revealed that under mild conditions, a high efficiency was achieved with over 55% cyclohexanol conversion and 80% cyclohexanone selectivity within 3 h. To gain a greater understanding of the reactive oxygen species involved, we conducted further quenching experiments and EPR analysis. Our findings suggested that·SO4-, ·OH, and mediated electron transfer played a dominant role in the oxidation process. The insights obtained from this work have the potential to offer a green and economically viable method for the selective oxidation of cyclohexanol to cyclohexanone.

ZIF-67-derived Co@NC as an efficient catalyst for magnesium sulfite oxidation in the flue gas desulfurization process

Magnesium desulfurization is a wet flue gas desulfurization (WFGD) technology widely used in China, however, the low oxidation rate of magnesium sulfite (MgSO3), a byproduct of WFGD, causes the subsequent oxidation and crystallization process to require amount energy. Here, we prepared a cobalt-based nitrogen-doped porous carbon catalyst (Co@NC) using ZIF-67 as a precursor for the efficient catalytic oxidation of MgSO3 generated during magnesium desulfurization. The performance of Co@NC catalysts obtained at an optimal calcination temperature of 650 °C showed that the catalysts with oxidation rates up to 0.1332 mmol·L−1·s−1 of MgSO3 were considerably better than those previously studied, which outperformed the catalysts described in earlier research by a considerable margin. Further studies revealed that the Co@NC’s exceptional catalytic activity was attributed to both its special porous structure and the exposed active Co sites in the organic skeleton. The uniformly dispersed Co species act as the active sites of the Co@NC that can be fully contacted with the reactant. The presence of 0.5 g·L−1 Co@NC increases the MgSO3 oxidation rate by about 14 times compared to the noncatalytic benchmark. A practical tactic is furnished by this research for energy saving and emission reduction in the WFGD process, especially for the efficient oxidation and resource conversion of the by-product MgSO3.

Renewable lignin-derived heteroatom-doped porous carbon nanosheets as an efficient oxygen reduction catalyst for rechargeable zinc-air batteries

Lignin upgrading to various functional products is promising to realize high-value utilization of low-cost and renewable biomass waste, but is still in its infancy. Herein, using industry waste lignosulfonate as the biomass-based carbon source and urea as the dopant, we constructed a heteroatom-doped porous carbon nanosheet structure by a simple NaCl template-assisted pyrolytic strategy. Through the synergistic effect of the NaCl template and urea, the optimized lignin-derived porous carbon catalyst with high content of active nitrogen species and large specific surface area can be obtained. As a result, the fabricated catalysts exhibited excellent electrocatalytic oxygen reduction activity, as well as good methanol tolerance and stability, comparable to that of commercial Pt/C. Moreover, rechargeable Zn-air batteries assembled with this electrocatalyst have a peak power density of up to 150 mW cm-2 and prominent long-term cycling stability. This study offers an inexpensive and efficient way for the massive production of highly active metal-free catalysts from the plentiful, inexpensive and environmentally friendly lignin, offering a good direction for biomass waste recycling and utilization.