Structure-performance Relationship Research Articles

Selective Upcycling of Polyethylene over Ru/H-ZSM-5 Bifunctional Catalyst into High-Quality Liquid Fuel at Mild Conditions.

It has been known that plastics with undegradability and long half-times have caused serious environmental and ecological issues. Considering the devastating effects, the development of efficient plastic upcycling technologies with low energy consumption is absolutely imperative. Catalytic hydrogenolysis of single-use polyethylene over Ru-based catalysts to produce high-quality liquid fuel has been one of the current top priority strategies, but it is restricted by some tough challenges, such as the tendency towards methanation resulting from terminal C-C cleavage. Herein, we introduced Ru nanoparticles supported on hollow ZSM-5 zeolite (Ru/H-ZSM-5) for hydrocracking of high-density polyethylene (HDPE) under mild reaction conditions. The implication of experimental results is that the 1Ru/H-ZSM-5 (~1 wt % Ru) acted as an effective and reusable bifunctional catalyst providing higher conversion rate (82.53 %) and liquid fuel (C5-C21) yield (62.87 %). Detailed characterization demonstrated that the optimal performance in hydrocracking of PE could be attributed to the moderate acidity and appropriate positively charged Ru species resulting from the metal-zeolite interaction. This work proposes a promising catalyst for plastic upcycling and reveals its structure-performance relationship, which has guiding significance for catalyst design to improve the yield of high-value liquid fuels.

Toward Developing Superior Cu-Based Metal-Organic Framework-Derived Materials for Electrocatalytic Oxidation of Ethanol.

This project addresses the urgent need for efficient and cost-effective development of electrocatalysts for the ethanol oxidation reaction (EOR). This reaction offers promising renewable energy solutions but faces challenges due to the slow EOR kinetics, typically requiring costly noble metal catalysts. To overcome these limitations, this study focuses on developing CuZn-based EOR catalysts derived from metal-organic frameworks (MOFs), focusing on understanding the structure-performance relationship between pristine MOF-based electrocatalysts and their pyrolyzed counterparts. Herein, bimetallic MOF materials with varying Cu/Zn ratios were synthesized, followed by pyrolysis to produce carbonized counterparts while preserving the fundamental structure but with altered physicochemical properties. Comparative EOR studies revealed the superior performance of pyrolyzed MOFs, demonstrating that optimized Zn-loading is crucial over Cu-based framework for catalyst performance and durability. Overall, this work highlights the potential of MOF-derived Cu-based catalysts for renewable energy applications and provides insights into optimizing their performance through controlled synthesis and post-treatment strategies.

Healing the structural defects of spinel MnFe2O4 to enhance the electrocatalytic activity for oxygen reduction reaction

Spinel metal oxides containing Mn, Co, or Fe (AB2O4, A/B = Mn/Fe/Co) are one of the most promising non-Pt electrocatalysts for oxygen reduction reaction (ORR) in alkaline conditions. However, the low conductivity of metal oxides and the poor intrinsic activities of transition metal sites lead to unsatisfactory ORR performance. In this study, eutectic molten salt (EMS) treatment is employed to reconstruct the atomic arrangement of MnFe2O4 electrocatalyst as a prototype for enhancing ORR performance. Comprehensive analyses by using XAFS, soft XAS, XPS, and electrochemical methods reveal that the EMS treatment reduces the oxygen vacancies and spinel inverse in MnFe2O4 effectively, which improves the electric conductivity and increases the population of more catalytically active Mn2+ sites with tetrahedral coordination. Moreover, the enhanced Mn-O interaction after EMS treatment is conducive to the adsorption and activation of O2, which promotes the first electron transfer step (generally considered as the rate-determining step) of the ORR process. As a result, the EMS treated MnFe2O4 catalyst delivers a positive shift of 40 mV in the ORR half-wave potential and a two-fold enhanced mass/specific activity. This work provides a convenient approach to manipulate the atomic architecture and local electronic structure of spinel oxides as ORR electrocatalysts and a comprehensive understanding of the structure-performance relationship from the molecular/atomic scale.

Transesterification of DMC with ethanol over K2CO3/Al2O3: The structure-performance relationship and catalytic mechanism

The transesterification of dimethyl carbonate (DMC) with ethanol to ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) has attracted increasing attention, which could be greatly promoted by heterogeneous solid base catalysts. The K2CO3/Al2O3 solid base catalysts with different active sites such as K2CO3, KAl(OH)2CO3, and KAlO2 were prepared for the transesterification reaction. The active sites of K2CO3 and KAl(OH)2CO3 mainly exist on the surface of KA-200 and KA-300, while K2CO3 and KAlO2 were mainly present on KA-400 and KA-500. The effects of active sites and the phase of support were studied systematically. KAl(OH)2CO3 showed higher activity than K2CO3 and KAlO2. In contrast, K2CO3 and KAlO2 displayed higher stability, with the activity of KA-400 kept stable over 2000 h. The excessive OH group of γ-AlOOH and water in the reaction system have a negative effect on the activity of the K2CO3/Al2O3 catalysts. The catalytic characterizations, transesterification reactions, and DFT calculations suggested that K+ in the KAl(OH)2CO3 species, with higher electron cloud density than that in K2CO3/γ-Al2O3, could efficiently promote the dissociation of ethanol and subsequent replacement of methoxy with ethoxy. The rate-determining step for the transesterification reaction was suggested to be the dissociation of ethanol.

Structure-performance relationship of polypropylene/elastomer/carbon black composites as high voltage cable shielding layer

As polypropylene (PP) is a competitive insulating material for next generation high-voltage cable, the corresponding PP based cable semi-conductive shielding layer material needs to be developed. This paper developed an excellent material prescription and proposed an analytical method of structure-performance relationship for the application and the evaluation of PP-based cable shielding layer. First, PP/POE/CB and PP/SEBS/CB composites with different carbon black (CB) loading were prepared and their electrical and mechanical properties were compared. Through thermal analysis technique, crystalline property and thermal stability of the composites were studied in detail. And the synchrotron radiation X-ray scattering techniques were employed to analyze the distribution of carbon black in the blend semi-quantitatively. The analysis result turns out the enrichment of carbon black in POE phase and its instability at high temperature limits its application under cable operation conditions. In contrast, PP/SEBS/CB30phr is recommended for lower thermal deformation, lower PTC effect and better mechanical parameters.

Disordering of Rh(111) single crystalline electrode surface in O2 saturated acid

The Rh(111) electrode shows superior oxygen reduction reaction (ORR) activity to Ir(111), contradicting the predicted trend based on the volcano plot. To unveil the origin for this, we investigate the interfacial structures of Rh(111) single crystalline electrode in 0.1 M HClO4 and 0.5 M H2SO4 solutions using cyclic voltammetry and potential step chronoamperometry under a hanging meniscus rotating disk electrode configuration. Our results reveal that i) in N2 saturated solution even at a potential below 0.20 V, oxygen-containing species adsorbates can be formed on the Rh(111) surface probably generated by oxidation of water; ii) Even under mild conditions, multiple cycles and current transients in O2 saturated solution at potentials where ORR taking place can cause significant surface disordering; iii) The disordering of the Rh(111) electrode induced by ORR exhibits similar base cyclic voltammograms to those of vicinal Rh(hkl) such as Rh(553) and Rh(332) etc., depending on the potentials applied during ORR, which, in turn, enhances the ORR activity in both 0.1 M HClO4 and 0.5 M H2SO4. These new findings provide valuable insights into the structure-performance relationship of ORR.

X-ray Spectroscopy at the SuperXAS and Debye Beamlines: from in situ to Operando.

Understanding structure-performance relationships are essential for the rational design of new functional materials or in the further optimization of (catalytic) processes. Due to the high penetration depth of the radiation used, synchrotron-based hard X-ray techniques (with energy > 4.5 keV) allow the study of materials under realistic conditions (in situ and operando) and thus play an important role in uncovering structure-performance relationships. X-ray absorption and emission spectroscopies (XAS and XES) give insight into the electronic structure (oxidation state, spin state) and local geometric structure (type and number of nearest neighbor atoms, bond distances, disorder) up to ~5 Å around the element of interest. In this mini review, we will give an overview of the in situ and operando capabilities of the SuperXAS beamline, a facility for hard X-ray spectroscopy, through recent examples from studies of heterogeneous catalysts, electrochemical systems, and photoinduced processes. The possibilities for time-resolved experiments in the time range from ns to seconds and longer are illustrated. The extension of X-ray spectroscopy at the new Debye beamline combined with operando X-ray scattering and diffraction and further developments of time-resolved XES at SuperXAS will open new possibilities after the Swiss Light Source upgrade mid 2025.

Uncovering Atomic-scale Dynamics in Solid Catalysts via X-ray-based Methods.

Deciphering the structural intricacies of catalysts is essential to advance their atomic-scale engineering. Solid catalysts are complex, with structural features spanning multiple length scales and involving dynamics, which possess challenges in understanding structure-performance relationships. However, advanced operando X-ray characterization techniques, including X-ray absorption spectroscopy (XAS), diffraction (XRD), and pair distribution function analysis (PDF) allow elucidation of structural features under working conditions, discovering transitions from supported nanocrystals to dispersed sites, from solid solutions to supported nanoparticles, or structural changes at the local level. In this mini-review, we discuss case studies exploring the structure of catalysts over different lengths and time scales under different applications, such as CO2 hydrogenation to methanol or the dry reforming of methane, using a combination of operando XAS, XRD and PDF.

Recent progress of waste plastic upcycling based on multifunctional zeolite catalysts

The chemical upcycling method is a promising strategy to alleviate the pollution problem of waste plastics by tapping into their intrinsic value and converting them into high value-added products. Zeolite-based catalysts are one of the surprising and efficient classes of thermocatalytic materials that have recently attracted considerable attention for waste plastic upcycling. They are designed for targeted applications with a wide range of adjustable acidic sites, multiple pore structures, and synergistic interactions with surface metals. In this review, we categorize plastics being converted into different high-value products and introduce the role of zeolite-based catalysts in the thermal upcycling of plastics. The structure-performance relationships of zeolite-based catalysts in catalytic reactions are discussed in depth. Finally, the future development of these multifunctional catalysts applied to the upcycling of plastics is outlined.

Linker Mediated Electronic-State Manipulation of Conjugated Organic Polymers Enabling Highly Efficient Oxygen Reduction.

Conjugated polymers with tailorable composition and microarchitecture are propitious for modulating catalytic properties and deciphering inherent structure-performance relationships. Herein, we report a facile linker engineering strategy to manipulate the electronic states of metallophthalocyanine conjugated polymers and uncover the vital role of organic linkers in facilitating electrocatalytic oxygen reduction reaction (ORR). Specifically, a set of cobalt phthalocyanine conjugated polymers (CoPc-CPs) wrapped onto carbon nanotubes (denoted CNTs@CoPc-CPs) are judiciously crafted via in situ assembling square-planar cobalt tetraaminophthalocyanine (CoPc(NH2)4) with different linear aromatic dialdehyde-based organic linkers in the presence of CNTs. Intriguingly, upon varying the electronic characteristic of organic linkers from terephthalaldehyde (TA) to 2,5-thiophenedicarboxaldehyde (TDA) and then to thieno/thiophene-2,5-dicarboxaldehyde (bTDA), their corresponding CNTs@CoPc-CPs exhibit gradually improved electrocatalytic ORR performance. More importantly, theoretical calculations reveal that the charge transfer from CoPc units to electron-withdrawing linkers (i.e., TDA and bTDA) drives the delocalization of Co d-orbital electrons, thereby downshifting the Co d-band energy level. Accordingly, the active Co centers with more positive valence state exhibit optimized binding energy toward ORR-relevant intermediates and thus a balanced adsorption/desorption pathway that endows significant enhancement in electrocatalytic ORR. This work demonstrates a molecular-level engineering route for rationally designing efficient polymer catalysts and gaining insightful understanding of electrocatalytic mechanisms.

Optimizing Selectivity in VOx/TiO2 Catalysts for Ammoxidation: Insights from Structure–Performance Relationships

Optimizing Selectivity in VO_<i>x</i>/TiO₂ Catalysts for Ammoxidation: Insights from Structure–Performance Relationships

Combining computational screening and machine learning to explore MOFs and COFs for methane purification

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have great potential to be used as porous adsorbents and membranes to achieve high-performance methane purification. Although the continuous increase in the number and diversity of MOFs and COFs is a great opportunity for the discovery of novel adsorbents and membranes with superior performances, evaluating such a vast number of materials in the quickest and most effective manner requires the development of computational approaches. High-throughput computational screening based on molecular simulations has been extensively used to identify the most promising MOFs and COFs for methane purification. However, the enormous and ever-growing material space necessitates more efficient approaches in terms of time and effort. Combining data science with molecular simulations has recently accelerated the discovery of optimal MOF and COF materials for methane purification and revealed the hidden structure–performance relationships. In this perspective, we highlighted the recent developments in combining high-throughput molecular simulations and machine learning to accurately identify the most promising MOF and COF adsorbents and membranes among thousands of candidates for separating methane from other gases including acetylene, carbon dioxide, helium, hydrogen, and nitrogen. After providing a brief overview of the topic, we reviewed the pioneering contributions in the field and discussed the current opportunities and challenges that we need to direct our efforts for the design and discovery of adsorbent and membrane materials.

Polyethyleneimine crosslinkers: Towards greener crosslinking and simultaneous conditioning of solvent-resistant nanofiltration polyimide membranes?

Crosslinked polyimide is a state-of-the-art membrane material for solvent-resistant nanofiltration (SRNF) and gas separation aiming for applications that involve harsh solvents or plasticizing components in the gas stream, respectively. Preparation of these membranes usually requires a multistep procedure involving hazardous diamine monomers. In this study, two hyperbranched polyethyleneimines (PEIs) with different molecular weights (800 and 25 000 g mol−1) were explored as crosslinking agents in the simultaneous (SIM) crosslinking -procedure where crosslinking takes place during coagulation in the non-solvent bath. Because of their lower volatility compared to traditional diamine crosslinkers, the manipulation of these polymeric forms of crosslinkers is intrinsically less hazardous. It is hypothesized that the conditioning step, a required post-processing step in membrane upscaling to allow subsequent potting, handling, and storage, can be omitted when crosslinking with such polymeric crosslinkers. Results showed how presence of PEI in the non-solvent bath influenced the course of phase inversion, resulting in a range of different membrane morphologies and performances. Drying unfortunately resulted in brittle membranes which lost most of their permeance. Even when residual PEI was allowed to remain in the membrane as a conditioning agent, low dried membrane permeances were obtained. By using PEI or other state-of-the-art crosslinkers prior to drying, light was shed on the structure-performance relationships governing permeance decline when drying SRNF membranes.

Zinc‐Ion Battery Chemistries Enabled by Regulating Electrolyte Solvation Structure

AbstractDesigning next‐generation alternative energy storage devices that feature high safety, low cost, and long operation lifespan is of the utmost importance for future wide range of applications. Aqueous zinc‐ion batteries play a vital part in promoting the development of portability, sustainability, and diversification of rechargeable battery systems. Based on the theory of electrolyte solvation chemistry, deep understanding of interaction between electrolyte components and their impact on the chemical properties has achieved a series of research progress. Analyzing the solvation shell of electrolyte or structure–performance relationship, and establishing more stable and high‐energy battery chemistries are inevitable requirements to suppress the electrolyte–electrode interphase side reaction and realize the functional use of zinc‐ion batteries. In this critical review, the attempt is to overview the current comprehension regarding the electrolyte solvation structure in zinc battery technology. Advanced methodology toward the interactions between zinc cations, solvent molecules, and anions in zinc aqueous electrolytes and the general rules for electrolyte design from the atomic level are summarized. Methods for viable solvation modification are then introduced regarding overcoming the remained challenges for transferring the laboratory results to next‐generation practical applications. Possible research direction with the aim of investigating the ultimate choice for future high‐performance electrolyte solvation construction is also outlined.

Toward better halon substitutes: Effects of carbon chain length on pyrolytic and fire-suppressing mechanisms of perfluoroalkanes

The use of halon fire extinguishants has led to the depletion of the ozone layer, prompting numerous international organizations to invest significant efforts in finding suitable halon alternatives. Among the counterparts, perfluorinated compounds stand out due to their environmental friendliness, specifically, CF3CF3, CF3CF2CF3 and CF3CF2CF2CF3 have been identified by NASA as the most promising candidates within this chemical family. This study digs into the impact of carbon chain length on thermal decomposition and fire suppression mechanisms of perfluoroalkanes with the three agents as model substances, employing experimental and theoretical analyses. Thermal decomposition products within the temperature range of 600 °C - 900 °C and fire suppression performances, including fire-extinguishing concentrations (9.38 vol.%, 7.81 vol.%, and 6.87 vol.%, respectively), variation of the flame morphology and temperature, are intensively analyzed and compared for the three perfluoroalkanes. Theoretical calculations indicate a decrease in carbon chain stability with the increasing chain length, and CF3CF2CF2CF3 manifests the most diversified self-decomposition paths at low energy barriers. Moreover, a wider spectrum of free radicals can be generated from the longer carbon chain via the CC cleavage, which can efficiently react with and continuously consume flame radicals (H• and OH•) to interrupt the combustion chain reaction. These findings enrich the structure-performance relationship of perfluoroalkanes, highlight the potential of specific perfluorinated compounds as viable halon alternatives and offer theoretical guidance for the selection and design of environmentally benign and efficient halon substitutes.

Multilaminate Energy Storage Films from Entropy-Driven Self-Assembled Supramolecular Nanocomposites.

Composite materials comprising polymers and inorganic nanoparticles (NPs) are promising for energy storage applications, though challenges in controlling NP dispersion often result in performance bottlenecks. Realizing nanocomposites with controlled NP locations and distributions within polymer microdomains is highly desirable for improving energy storage capabilities but is a persistent challenge, impeding the in-depth understanding of the structure-performance relationship. In this study, a facile entropy-driven self-assembly approach is employed to fabricate block copolymer-based supramolecular nanocomposite films with highly ordered lamellar structures, which are then used in electrostatic film capacitors. The oriented interfacial barriers and well-distributed inorganic NPs within the self-assembled multilaminate nanocomposites effectively suppress leakage current and mitigate the risk of breakdown, showing superior dielectric strength compared to their disordered counterparts. Consequently, the lamellar nanocomposite films with optimized composition exhibit high energy efficiency (>90% at 650MVm-1), along with remarkable energy density and power density. Moreover, finite element simulations and statistical modeling have provided theoretical insights into the impact of the lamellar structure on electrical conduction, electric field distribution, and electrical tree propagation. This work marks a significant advancement in the design of organic-inorganic hybrids for energy storage, establishing a well-defined correlation between microstructure and performance.

Nature of C-C coupling and strategy of tuning the catalytic activity of Cu-N-C catalysts for electro-reduction of CO2 to ethanol

With high atomic utilization and remarkable catalytic activity, Cu-N-C type catalysts display great potential for electro-catalysis in CO2 reduction. However, the relationship between the active moiety and catalytic activity of generating high-value C2 products is still unclear, and the explicit screening criteria is scarcity. Herein, based on the first-principle simulation, the structure-performance relationship on Cu-N-C type catalysts has been investigated by modulating the CO2 reduction process as the number of Cu atom (Cu1, Cu2, Cu3) and the ligand environment (B, C, N, O, P, S) changed. We find the adsorption strength of intermediate *CO strongly affect the possibility of C-C coupling, which can be determined by Bader charge on Cu atom, mainly depending on the number of loaded atomic Cu on Cu-N-C catalysts. Furthermore, the Bader charge can be refined by adjusting the coordination atom of Cu, thus optimizing catalytic activity for the CO2 to ethanol. The moderate Bader charge value, between +0.35 and +0.45, enables the catalyst to behave as a potentially excellent activity with low limiting potential for generating ethanol. More importantly, an intrinsic descriptor, composed of the radius, electronegativity, and number of valence electrons of coordination atoms (φ=∑χ∑r*∑np), was established to characterize the catalytic activity of Cu-N(X)-C catalysts for producing ethanol. Two excellent catalysts, Cu3-N2O2 (-0.51 V) and Cu3-N3S (-0.64 V), are screened out for the CO2RR to generate ethanol. This work discloses theoretical basis for catalytic selectivity of C2 products on Cu-N-C catalysts and provides a regulating and screening principle for high performance catalysts to ethanol.

Assembling copper and cerium into TNU-9-type periodic microporous organosilicas for the selective catalytic reduction of NOx by NH3

TNU-9-type periodic microporous organosilicas material containing Ce and Cu was assembled by organic-inorganic hybrid method and then calcined to acquire CuCex@PMO-TNU-9 catalyst. The effect of cerium on the structure-performance relationship was studied. The results indicated that the (CuCex@PMO-TNU-9 x = 1.0, 1.5 and 2.0) catalysts were successfully prepared, whereas CuCe2.5@PMO-TNU-9 was not successfully prepared due to the excess of the precursor resulting in the difference of hydrolysis rate between the organosilane precursor and white carbon black. The CuCe2@PMO-TNU-9 catalyst showed higher NH3-SCR activity than Cu@PMO-TNU-9, which was because that the interaction between Ce and Cu could form Cu2++Ce3+↔Cu++Ce4+ redox cycle, which promoted the oxidation of NO to NO2, forming “fast SCR” reaction. More importantly, CuCe2@PMO-TNU-9 catalyst had excellent the resistance of H2O and SO2 due to the excellent hydrophobicity of the TNU-9 zeolite and the sacrificial site Ce protecting the active site Cu.

Investigation on the pore structure-performance relationship of porous carbon adsorbents for SF6/N2 separation via fine pore modulation

The capture and recovery of SF6 as electron specialty gas from SF6/N2 by adsorptive separation have obvious advantages such as the mitigation of greenhouse effect and resource utilization of waste gas. The comprehensive understanding of pore structure-performance relationship of porous materials is beneficial for guiding the design of highly-efficient adsorbents for separating SF6/N2, but is presently limited. In this work, a series of citric acid (CA) and KOH with different molar ratios are designed to synthesize carbon adsorbents denoted as CAK via a one-step carbonization-activation method and probed for the adsorptive separation of SF6/N2. Characterization results reveal that the micropores in carbon adsorbents are finely tuned from 0.73 to 0.88 nm at an angstrom level through increasing the KOH/CA molar ratios in precursors, and the significant mesopores are formed in CAK4. Static adsorption results indicate that the SF6 adsorptive capacity at low pressure of 10 kPa increases and then decreases with the increasing contents of KOH, and the highest value is obtained in CAK2, while the diffusion rates illustrated from the adsorption kinetics continuously increase. By correlating the pore structures with adsorption capacity of adsorbents, the critical role of micropores with size ≤ 0.9 nm in determining the SF6 capacity at 10 kPa and mesopores in enhancing the mass transfer is quantitatively confirmed. The dynamic breakthrough results of CAKx carbon adsorbents for SF6/N2 separation are well explained with these understandings, which are important for guiding the design of porous adsorbents with high-performance for SF6 capture and recovery.

Photocatalytic CO2 methanation over the Ni/SiO2 catalysts for performance enhancement

CO2 methanation produces synthetic natural gas, which reduces CO2 emission and generates sustainable energy. Exploring effective approach and developing high performance Ni catalysts are the main focus for the reaction. In this study, we report photocatalytic methanation over Ni/SiO2 catalysts. Through physicochemical properties of BET, XRD, H2-TPR and TEM, optical properties of UV–visual light absorbance and light-illuminated H2-TPR, and the performance of photocatalytic methanation, the structure-performance relationship is tentatively discussed. The strong absorbance of light, the small size of Ni nanoparticles and the strong metal-support interaction of the Ni/SiO2 catalysts, as well as the low activation energy of CH4 production, are correlated to the enhanced photocatalytic performance compared to the conventional catalytic performance. The photocatalytic pathway of methanation on Ni nanoparticles are suggested to understand the enhanced performance. The work demonstrates the higher photocatalytic methanation performance than conventional catalytic methanation, which is applicable for other reactions using photo-sensitive catalysts.