Secondary Pyrolysis Research Articles

Unlocking the Effects of the RuCo Alloy Ratio on Alkaline Hydrogen Production.

Understanding the interaction between Ru and Co components and the alloy ratio effects on the catalytic process is a technical challenge that requires a precise alloy structural design. This study proposes an effective stepwise annealing method for the construction of RuCo alloy-based electrocatalysts with varied Ru:Co ratios. Interestingly, as the concentration of Co in the first-step pyrolysis products increases, the secondary pyrolysis results in RuCo composites undergoing a transition from incomplete alloying to alloy ratios of 1:1, 1:2, and 1:8. When the alloy ratio is 1:1, more Run+ and Co0 transform into Ru0 and Co2/3+. In 1 M KOH, RuCo-0.6/NC demonstrates outstanding catalytic performance and durability even superior to that of commercial Pt/C, delivering a lower overpotential of 16 mV at 10 mA cm-2. DFT calculations reveal that the fast H2O dissociation and moderate H adsorption guarantee the superior activity of RuCo.

Deactivation of chromated copper arsenate as a catalyst in smouldering of wood

Chromated copper arsenate (CCA) is a preservative treatment that enhances the biodegradation resistance of wood, essential for prolonging the service life of exterior infrastructure. However, the susceptibility of CCA-treated wood to smouldering combustion presents a significant challenge, as the metals present in the CCA catalyze the smouldering. In this work, we examined the oxidative behaviour of char produced from CCA-treated wood through dynamic thermogravimetric analysis. There was a gradual decrease in the catalytic activity of the CCA as temperature increased, particularly above 400 °C. At this stage, lignin undergoes secondary pyrolysis, and thermal decomposition of CCA complexes occurs. The thermal decomposition of CCA-treated wood at temperatures above 650 °C was similar to that of untreated wood, indicating the possible deactivation of the CCA. The agglomeration of species containing Cu or Cr above 650 °C might be responsible for the deactivation. This process is influenced by simultaneous lignin pyrolysis and decomposition of CCA complexes, which are also likely contributors to the loss of CCA's catalytic activity. This research introduced a novel experimental approach to assess the catalytic effects of CCA on char oxidation at elevated temperatures, offering valuable insights into CCA deactivation and its implications for fire safety. It also contributes to the development of potential modifications to CCA formulations aimed to reduce smouldering in wildfire-prone regions.

Volatile-char interactions during biomass pyrolysis: Effects of functionalized graphitized carbon nanotubes on volatile distribution of cellulose and its model compounds

Volatile-char interactions are prevalent in biomass pyrolysis processes. To gain deeper insights into their impact on biomass pyrolysis volatile distribution, interactions between volatile compounds and char during flash pyrolysis of glucose, cellobiose, and cellulose were investigated using a pyrolysis–gas chromatography/mass spectrometry detection technique, by modifying both the chain lengths of the raw materials and the functional groups of graphitized multi-walled carbon nanotubes (CNTs). The results reveal that volatile-char interactions markedly influence the distribution of the final pyrolysis products derived from glucose-based compounds. In the presence of any type of CNTs, dehydrated saccharides in the primary products, particularly levoglucosan (LG), exhibit the highest sensitivity to the interactions. Consequently, primary products such as LG and 5-hydroxymethylfurfural (HMF) undergo secondary pyrolysis, yielding compounds such as levoglucosenone (LGO) and 5-methyl-2-furancarboxaldehyde (FCM). Additionally, CNTs without functional groups are advantageous for the production of expensive LGO (The relative abundance reached 9.65%), whereas the relative abundance of FCM increases significantly with hydroxyl-, carboxyl-, and amino-modified carbon nanotubes. Particularly, the relative abundance of FCM is highest in the presence of amino-modified carbon nanotubes, regardless of whether the feedstock is glucose, cellobiose, or cellulose, with values of 25.14%, 23.32%, and 4.23%, respectively. Furthermore, consistent changes in product distribution trends among different glucose-based compounds under identical CNT conditions suggest that glycosidic bonds have minimal impact on volatile-char interactions.

Atomically dispersed ternary FeCoNb active sites anchored on N-doped honeycomb-like mesoporous carbon for highly catalytic degradation of 4-nitrophenol

In the last decades, 4-nitrophenol is regarded as one of highly toxic organic pollutants in industrial wastewater, which attracts great concern to earth sustainability. Herein, atomically dispersed ternary FeCoNb active sites were incorporated into nitrogen-doped honeycomb-like mesoporous carbon (termed FeCoNb/NHC) by a two-step pyrolysis strategy, whose morphology, structure and size were characterized by a set of techniques. Further, the catalytic activity and reusability of the as-prepared FeCoNb/NHC were rigorously examined by using 4-NP catalytic hydrogenation as a proof-of-concept model. The influence of the secondary pyrolysis temperature on the catalytic performance was investigated, combined by illuminating the catalytic mechanism. The resultant catalyst exhibited significantly enhanced catalytic features with a normalized rate constant (kapp) of 1.2 × 104 min-1g−1 and superior stability, surpassing the home-made catalysts in the control groups and earlier research. This study provides some constructive insights for preparation of high-efficiency and cost-effectiveness single-atom nanocatalysts in organic pollutants environmental remediation.

Preparation of Al-doped carbon materials derived from artificial potassium humate prepared from waste cotton cloth and their excellent Cr(VI) adsorption performance

Millions of tons of cotton textile waste are generated annually worldwide, and most of it enters the municipal solid waste (MSW) stream for landfill or incineration disposal, resulting in a significant waste of resources and environmental pollution. This article developed an innovative low-temperature pyrolysis process for producing artificial humic acid (HA) from waste cotton textiles. Subsequently, Al3+ was introduced for a secondary pyrolysis to prepare an Al-doped biochar (Al/BC) with superior adsorption properties. The experimental results show that the presence of Al3+ has an important influence on the pyrolysis process of cotton fabric and the formation and structure of Al/BC. This is the first time to synthesize low-cost adsorbent by pyrolysis and aluminum mixing process of waste cotton cloth and explains the mechanism. This increased in defects (ID/IG = 0.76 to ID/IG = 0.92), a larger specific surface area (6.47 m2/g to 566.94 m2/g), and an increase in oxygen-containing functional groups (from none to C-O-C, OC-O, etc.) when compared to the undoped Al3+ biochar. The optimum Al3+-doped biochar (Al/BC-15) prepared with HA as a precursor exhibited a superior adsorption capacity for Cr(VI) of up to 176.23 mg/g, surpassing the results reported for similar materials in the literature. The adsorption mechanism of Cr(VI) is primarily based on physical adsorption, with some chemical adsorption. At a lower pH, the Al/BC-15 surface exhibits a high positive charge (46 mV). The Al3+-O-Cr(VI) association group is formed through rapid electrostatic attraction between C-Al and Cr(VI). Due to the strong positive electronegativity of Al3+ and the negative electronegativity of C in the vicinity of Al, Cr(VI) is further reduced to Cr(III) by C-Al. Therefore, the method proposed in this paper for preparing Al-doped carbon materials from waste cotton fabric offers a new approach and potential application for the production of high-performance adsorbent materials from waste cotton fabric.

Comparison of secondary hydrothermal and pyrolysis in biomass carbon-based materials: activation methods and surface properties

Comparison of secondary hydrothermal and pyrolysis in biomass carbon-based materials: activation methods and surface properties

Coupling of Fe-Nx sites and Fe nanoparticles on nitrogen-doped porous carbon for boosting oxygen electroreduction in Zn-air batteries

Fe and nitrogen co-doped carbon (Fe-N-C) catalysts have emerged as attractive materials to substitute Pt-based catalysts for the oxygen reduction reaction (ORR) in Zn-air batteries (ZABs). However, the Fe-N-C catalysts with monotypic active component usually endow suboptimal catalytic performance and stability under both acid and alkaline medium. Herein, a nano ZnO template and two-step pyrolysis co-assisted strategy is proposed to achieve the coupling of Fe-Nx sites and metallic Fe nanoparticles in hierarchically porous N-doped carbon for ORR. The nano ZnO template contributes to the formation of meso/macropores structure, while the secondary pyrolysis is beneficial to the creation of more micropores. Besides the advanced hierarchical porosity, the combination of dispersed Fe-Nx sites and dominated metallic Fe nanoparticles is also conducive to boost ORR activity in both acid and alkaline solution. Impressively, the prepared Fe@FeHPNC-P2 electrocatalyst exhibits an excellent half-wave potentials (E1/2) of 0.88 V and 0.79 V in alkaline and acidic electrolyte, respectively. Meanwhile, the assembled liquid Zn-air battery using Fe@FeHPNC-P2 delivers a peak power density of 149.3 mW cm−2 and a maximum energy density of 957.1 Wh kgZn−1 along with long-term stability for 1000 cycles.

Regulation of d‐Orbital Electron in Fe‐N4 by High‐Entropy Atomic Clusters for Highly Active and Durable Oxygen Reduction Reaction

AbstractSimultaneously improving activity and stability is a crucial yet challenge in the development of metallic single‐atom‐based catalysts. In current work, a novel approach is introduced to address this issue by combining post‐adsorption and secondary pyrolysis techniques to create a synergistic catalytic system, in which the single atoms (SAs) Fe sites played in the NC matrix (Fe─NC) are coupled with high‐entropy atomic clusters (HEACs). Theoretical calculations reveal that the incorporation of HEACs lead to a rehybridization of the 3d orbital configuration of Fe‐N4, which helps to balance the adsorption/desorption energy of oxygenated intermediates. In situ spectroscopy further reveals that the rate‐limiting step of OH* desorption on HEAC/Fe─NC in oxygen reduction reaction (ORR) is more facile compared to atomic Fe─NC, implying a higher ORR activity. Moreover, the synergistic effect of diffusion activation barriers and configuration entropy contributes to the structural stability of HEAC/Fe─NC, resulting in remarkable durability. Consequently, this unique catalyst exhibits half‐wave potentials of 0.927 and 0.828 V in an aqueous solution of KOH (0.1 m) and HClO4 (0.1 m), respectively, along with excellent durability. The findings propose a novel strategy for modulating the electronic structure of metallic SAs catalysts and enhancing their stability through strong interactions between SAs and HEACs.

Microwave-enhanced pyrolysis of bamboo for furfural-rich bio-oil production over WS2 catalyst

The efficient utilization of bamboo waste has attracted increasing interest as a promising solution to address the challenges associated with climate change and promote a more environmentally friendly approach to resource utilization. Herein, we demonstrated the highly selective production of furfural from bamboo through a microwave-assisted pyrolysis (MAP) process using WS2 catalysts. Firstly, the content of furfural can be precisely regulated by manipulating key process conditions such as microwave power, temperature and the mass ratio of WS2 to bamboo. Notably, compared to non-catalyzed MAP, the presence of the WS2 catalyst significantly enhanced the production of both furfural and furan components. The optimal content of furfural and furan components reached up to 66.9 area% and 75.6 area% in bio-oil under the conditions of 700 W, 400 °C and a 3:10 WS2 to bamboo ratio for 15 min. Furthermore, the liquid oil mainly consisted of C5 and C6 products (86.5 area%), indicating that MAP enhances the selectivity of small molecular products and furan compounds when coupled with the WS2 catalyst. Experimental results revealed that WS2 played bifunctional roles as a microwave absorbent and catalyst, promoting the bio-oil content and limiting the secondary pyrolysis of furan components, leading to a high selectivity of furan and a high content of furan products. This work provides valuable insights into producing furan-rich bio-oil from bamboo through MAP over transition metal dichalcogenides materials.

Asymmetric Coordination of Bimetallic Fe-Co Single-Atom Pairs toward Enhanced Bifunctional Activity for Rechargeable Zinc-Air Batteries.

The advancement of rechargeable zinc-air batteries (RZABs) faces challenges from the pronounced polarization and sluggish kinetics of oxygen reduction and evolution reactions (ORR and OER). Single-atom catalysts offer an effective solution, yet their insufficient or singular catalytic activity hinders their development. In this work, a dual single-atom catalyst, FeCo-SAs, was fabricated, featuring atomically dispersed N3-Fe-Co-N4 sites on N-doped graphene nanosheets for bifunctional activity. Introducing Co into Fe single-atoms and secondary pyrolysis altered Fe coordination with N, creating an asymmetric environment that promoted charge transfer and increased the density of states near the Fermi level. This catalyst achieved a narrow potential gap of 0.616 V, with a half-wave potential of 0.884 V for ORR (vs the reversible hydrogen electrode) and a low OER overpotential of 270 mV at 10 mA cm-2. Owing to the superior activity of FeCo-SAs, RZABs exhibited a peak power density of 203.36 mW cm-2 and an extended cycle life of over 550 h, exceeding the commercial Pt/C + IrO2 catalyst. Furthermore, flexible RZABs with FeCo-SAs demonstrated the promising future of bimetallic pairs in wearable energy storage devices.

Effect of high-pressure pyrolysis on syngas and char structure of petroleum coke

Petroleum coke, a byproduct of petroleum refining, is considered a potential alternative fuel owing to its low ash content and high calorific value. This study aims to enhance our understanding of the pyrolysis process and its potential applications by investigating the effect of pressure on the pyrolysis of petroleum coke, focusing on changes in its syngas composition and char structure. High-pressure pyrolysis was employed to explore structural changes, decomposition pathways, and gas production. High pressures increase the residence time and promote secondary pyrolysis, leading to the increased production of hydrogen. Also, high pressure can promote gasification reactions such as methanation. The influence of pressure on the chemical and physical structures of the produced char was also observed. Higher pressures resulted in more active secondary pyrolysis, causing a decrease in the aromatic groups and an increase in the aliphatic and oxygen-containing groups in the char. The surface area and porosity of char increased at higher pressures, enhancing its reactivity and gasification rate. Overall, this study provides valuable insights into the effects of pressure on petroleum coke pyrolysis, shedding light on its potential as an alternative energy resource and highlighting changes in gas composition and char structure under various pressure conditions.

Effect of biochar structure on the selective adsorption of heavy components in bio‐oil

AbstractIn this study, biochars with different structures were prepared through HNO3 oxidation and secondary pyrolysis to study the relationship between the structure of biochar and its selectivity for the adsorption of light and heavy aromatics in bio‐oil. The results showed that the adsorption rates of biochar with different structures ranged from 2.90 to 4.00 g bio‐oil per g biochar. The influence of pore structure was dominant, followed by the influence of O‐containing functional groups and the degree of graphitization. The higher the adsorption capacity of biochar for bio‐oil, the smaller the concentrations of the light aromatic model compounds in the absorbed bio‐oil (ABO). Among the five light aromatics, biochar has the best adsorption selectivity for dihydroxybiphenyl and the worst for eugenol and propyl phenol. This is attributed to the diphenyl ring structure of dihydroxybiphenyl, which makes it more susceptible to adsorption, and other light model compounds only have one benzene ring. In summary, biochar demonstrates better adsorption selectivity for heavy aromatics than light aromatics. The more developed the pore structure is, the more enriched O‐containing functional groups are, and the higher the graphitization degree of biochar is, the better the selective adsorption of aromatic compounds in bio‐oil.

Experimental and reactive molecular dynamics simulation of municipal sludge extract pyrolysis

The sludge extract obtained from degradation solvent extraction exhibits high carbon content, low oxygen content, and ash-free characteristics, making it an ideal fuel due to its excellent performance. In this study, the pyrolysis process of the extract was systematically studied by combining GC-MS experiment with ReaxFF molecular dynamics simulation. The comparison between GC-MS experimental results and ReaxFF-MD simulation shows a high degree of similarity, thus confirming the accuracy of the simulation. This study identified 2000 K as the turning temperature between initial pyrolysis and secondary pyrolysis. In the temperature range of 1200–2000 K, the extract mainly undergoes primary pyrolysis, while in the temperature range of 2000–3000 K, the secondary reaction is remarkable, which is characterized by the further decomposition of tar free radicals and the condensation reaction involving tar free radicals or char. The analysis of typical gas content shows that H2, CO, NH3 and HCN are by-products of the secondary reaction of tar, and there are a lot of reducing gases at high temperature, such as H2, CO and CH4. Finally, the migration patterns of carbon, hydrogen, oxygen and nitrogen are discussed. It is worth noting that hydrogen and nitrogen mainly migrate to the pyrolysis gas phase. This not only laid a foundation for the separation of nitrogen and hydrogen in the future, but also triggered thinking about the potential of “low-carbon emission resource” in future research work. When compared to raw municipal sludge, the initial pyrolysis temperature of municipal sludge extract is much lower, and its pyrolysis process becomes faster. The advantages of reactive gas components indicate that it is more reactive. This variance results in a distinct product distribution and pyrolysis mechanism.

Adsorption Performance and Mechanism of Oxytetracycline in Water by KOH Modified Biochar Derived from Corn Straw

The pollution control of tetracycline antibiotics in the environment has become a hot topic, and biochar adsorption has become an important technology to remove organic pollutants. Pyrolytic biochars (BC400, BC500, and BC600) were prepared from corn straw and then were modified by KOH to obtain KBC400, KBC500, and KBC600. Among them, KBC400 was selected for secondary pyrolysis activation at 400-600℃ to obtain AKBC400, AKBC500, and AKBC600. The structure characteristics and surface properties of AKBC were also characterized. The adsorption kinetics and thermodynamic characteristics of oxytetracycline hydrochloride (OTC) in the solution by AKBC were investigated using batch experiments. Compared to that of BC400, the specific surface area and pore structure of AKBC were significantly improved, and the aromaticity was also enhanced, resulting in the notable enhancement of the adsorption capacities for OTC. The pseudo-second-order kinetics model could better fit the adsorption process, and AKBC500 had the largest adsorption rate constant and capacity. Both the intraparticle diffusion and film diffusion were the rate-limiting steps. The Langmuir, Freundlich, and Temkin models could fit the adsorption isotherms perfectly. The adsorption of OTC on AKBC was a spontaneous, endothermic, and entropy-increasing process by both physisorption and chemisorption. The pH values in the range of 3.0-7.0 were favorable for the adsorption of OTC by AKBC. The adsorption capacity decreased with the humic acid concentration over 10 mg·L-1. The adsorption mechanism of OTC by AKBC involved pore filling, hydrogen bonding, π-π conjugation, cation-π bond, and strong electrostatic effect. AKBC still had good reusability for OTC removal after five times of regeneration. The obtained AKBC is a potential adsorbent for OTC removal from water due to the good pore structure, high adsorption capacity, and stable adsorption effect.

Hierarchical-Pore-Stabilization Strategy for Fabricating 18.3 wt% High-Loading Single-Atom Catalyst for Oxygen Reduction Reaction.

Metal single-atom catalysts (M-SACs) attract extraordinary attention for promoting oxygen reduction reaction (ORR) with 100% atomic utilization. However, low metal loading (usually less than 2 wt%) limits their overall catalytic performance. Herein, a hierarchical-structure-stabilization strategy for fabricating high-loading (18.3%) M-SACs with efficient ORR activity is reported. Hierarchical pores structure generated with high N content by SiO2 can provide more coordination sites and facilitate the adsorption of Fe3+ through mesoporous and confinement effect of it stabilizes Fe atoms in micropores on it during pyrolysis. High N content on hierarchical pores structure could provide more anchor sites of Fe atoms during the subsequent secondary pyrolysis and synthesize the dense and accessible Fe-N4 sites after subsequent pyrolysis. In addition, Se power is introducedto modulate the electronic structure of Fe-N4 sites and further decrease the energy barrier of the ORR rate-determining step. As a result, the Fe single atom catalyst delivers unprecedentedly high ORR activity with a half-wave potential of 0.895V in 0.1M KOH aqueous solution and 0.791V in 0.1M HClO4 aqueous solution. Therefore, a hierarchical-pore-stabilization strategy for boosting the density and accessibility of Fe-N4 species paves a new avenue toward high-loading M-SACs for various applications such as thermocatalysis and photocatalysis.

Facile synthesis of single‐nickel‐atomic dispersed mesoporous carbon nanosheets with controllable nitrogen doping for efficient electrochemical CO2 reduction

AbstractThe catalytic conversion of CO2 into high value‐added chemical products driven by electricity was an effective strategy to reduce atmospheric CO2 concentration. The development of high efficiency catalysts had always been the core for electrocatalytic reduction of CO2. The single transition metal sites anchored on nitrogen‐doped carbon showed great potential in CO2 reduction reaction (CO2RR). In this paper, the atomically dispersed Ni−N sites are constructed on the two‐dimensional mesoporous carbon nanosheets by the secondary pyrolysis method. The rich mesoporous structure of the two‐dimensional nanosheets is beneficial to CO2 diffusion and adsorption during CO2RR, and the high nitrogen contents could increase the Ni single atom loadings. The nitrogen content and type could be controlled by regulating the ratio of nitrogen source to carbon source, and the catalyst activity is improved as the proportion of nitrogen sources increases. When the ratio of nitrogen source to carbon source is four, the oxidation state of Ni single atoms Ni@NMCN4 is between 0 and +2, and Ni single atoms exists as Ni−N4 structure with pyridinic N of 32.78 %, which exhibits the best electrochemical CO2RR activity. The active site of Ni@NMCN4 is confirmed as the highly stable Ni single atoms. Moreover, the pyridinic N species are proved to play an important role in enhancing the CO2 electroreduction performance. This work provides a new perspective to adjust the nitrogen content and type in transition metal monatomic‐N‐doped carbon electrocatalysts for CO2RR.

Removal of ciprofloxacin lactate by phosphoric acid activated biochar: Urgent consideration of new antibiotics for human health

The long-term accumulation and residue of the emerging pollutant ciprofloxacin lactate (CIP) in the aquatic environment have caused great harm to the ecological environment. In this experiment, CIP was adsorbed on H3PO4-activated cow dung biochar (PBC) prepared with different impregnation ratios. It was found that the secondary pyrolysis of activated original biochar leads to more thorough carbonization, increased aromaticity, hydrophobicity, increased porosity, and increased hydroxyl, carboxyl, carbonyl and a large number of functional groups. When pH value was 5.0, 30P-BC had the highest adsorption capacity. The fitting correlation of PSO models for BC, 10P-BC, 30P-BC, and 50P-BC is higher, with the correlation coefficients of 0.9930, 0.9917, 0.9874, and 0.9886, respectively. The maximum adsorption capacity of materials were 15.27 mg/g (BC), 39.97 mg/g (10P-BC), 53.89 mg/g (30P-BC) and 22.04 mg/g (50P-BC), respectively. The four adsorbents are dominated by single molecule layer chemical adsorption, and there is also a physical adsorption process. The primary mechanism of CIP is the interaction between pore filling and π-π electron donor acceptor, which also includes electrostatic and hydrogen bonding. The removal efficiency applied to actual wastewater and the health assessment of human health risks are worth considering. The removal rate of CIP by 30P-BC in the simulated wastewater experiment reached 97.77 %. Moreover, through the model fitting of the polluted water quality contribution rate to human health exposure, the removal of CIP by 30P-BC can greatly reduce the related risks to human health.

Preparation of Biochar Composite Microspheres and Their Ability for Removal with Oil Agents in Dyed Wastewater.

Oil agents produced from the degreasing treatment of synthetic fibers are typical pollutants in wastewater from printing and dyeing, which may cause large-scale environmental pollution without proper treatment. Purifying oily dye wastewater (DTY) at a low cost is a key problem at present. In this study, biochar microspheres with oil removal ability were prepared and derived from waste bamboo chips using the hydrothermal method. The structure of the biochar microsphere was regulated by activation and modification processes. Biochar microspheres were characterized, and their adsorption behaviors for oily dye wastewater were explored. The results show that the adsorption efficiency of biochar microspheres for oily dye wastewater (DTY) was improved significantly after secondary pyrolysis and the lauric acid grafting reaction. The maximum COD removal quantity of biochar microspheres for DTY was 889 mg/g with a removal rate of 86.06% in 30 min. In addition, the kinetics showed that chemisorption was the main adsorption manner. Considering the low cost of raw materials, the application of biochar microspheres could decrease the cost of oily wastewater treatment and avoid environmental pollution.

Atomically Dispersed Transition Metal-Nitrogen-Carbon Electrocatalysts: Design, Synthesis, Characterization, Reactivity and Durability

Platinum group metal-free (PGM-free) catalysts have been targeted as possible Earth Abundant Elements solution to many electrochemical energy conversion technologies. Special attention has been given to PGM-free electrocatalysis with atomically dispersed (AD) transition metal moieties decorated over nitrogen-doped carbonaceous materials (a.k.a. M-N-C catalysts). Major applications for M-N-Cs are in cathode catalysts for oxygen reduction reaction (ORR). 1 These materials are employed across the pH-range: in proton exchange membrane fuel cells (PEMFC), biological (microbial) fuel cells (MFC) and alkaline, including anion/hydroxyl exchange membrane fuel cells (AFC, AEMFC/HEMFC). We have successfully introduced M-N-C catalysts synthesized by sacrificial support method (SSM) as a hard template approach based on high temperature pyrolysis.2 In most cases a secondary pyrolysis is being performed to promote AD display of the transition metal.3 This talk will address structure-to-property correlations for M-N-C catalysts in ORR based on electrochemical activity obtained in rotating ring-disk electrodes (RRDE) with those spectroscopic and microscopic observations and density functional theory (DFT) calculations of oxygen binding on AD transition metal. We will discuss the role of the AD transition metal, participation of the surface N-groups as co-catalysts/alternative active sites and the possible role of surface oxides as co-catalysts or hydrophilic/hydrophobic properties descriptor. M-N-C catalysts performance in single membrane electrode assembly (MEA) fuel cells will also be discussed in the context of its surface chemistry and materials structure/morphology. We will focus on local hydrophobicity of SSM-based M-N-C electrocatalystsand its impact on the MEA performance.A broad spectrum of AD transition metal decorated MNCs have been synthesized and evaluated for catalytic activity in ORR (and other processes). The use of such materials as “active supports” for highly dispersed platinum or platinum alloy nanoparticles will be discussed. New developments in synthesis protocols enabling “green chemistry” scalable solutions will be discussed.

Theoretical study on the catalytic pyrolysis mechanism of polyethylene terephthalate dimer

ABSTRACT In this paper, the density functional theory of B3P86/6–31++G(d,p) method was used to study the mechanism of the catalytic pyrolysis reactions of PET dimer. The calculated results show that the reaction energy barrier for calcium oxide to capture a proton on carboxyl group (at 112.6 kJ/mol) is lower than that on alkyl group (at 153.3 ~ 170.0 kJ/mol), which is more conducive to decarboxylation reaction. The protons provided by the acid catalyst attack the oxygen atoms of the C=O bond of PET main chain to form the cationic intermediate, and then the cleavage reaction occurs on the Calkyl-O bond, of which the bond dissociation energy is the lowest at 46.9 ~ 62.4 kJ/mol. Compared with pure pyrolysis, catalysts have little effect on the components of initial pyrolysis products, but it has effects on the components of secondary pyrolysis products of PET. The addition of catalysts can change the components of secondary pyrolysis products by changing the optimal reaction path of degradation. During the reaction processes, both alkaline and acidic catalysts can reduce the reaction energy barriers of the main elementary reactions to a certain extent (from 251.3 ~ 264.6 kJ/mol to 112.6 ~ 170.0 and 46.9 ~ 169.1 kJ/mol, respectively), making the reactions easier to proceed.