Energy Storage Materials Research Articles

Upcycling drinking bottle waste to intercalated 2D-0D carbon architectures and its supercapacitor applications

Despite its many benefits to our modern life, plastic contributes a large volume of solid waste that increasingly threatens our environment and health. Through a hydrothermal depolymerization and carbonization process that involves nitric acid and ethanol, drinking bottles that are made of polyethylene terephthalate are successfully converted into carbon quantum dots (CDs) and thin carbon nanosheets simultaneously with the former intercalated between layers of the latter to form a unique ball-sheet architecture. When used as electrode material, the stacking carbon nanosheets in this plastic-derived, ball-sheet carbon (PBSC) structure create a conductive network to allow rapid transport of ions and electrons while the well-dispersed CDs offer a large surface area and numerous sites to host them. The supercapacitors made of these PBSC electrodes exhibit double-layer capacitor behaviors with a specific capacity reaching 237 F/g at a charge rate of 1 A/g and excellent cycling stability. Our efforts offer a new route to upcycle plastic waste as valuable energy storage materials, which may help boost its recycling and the sustainable deployment of various clean energy resources.

Oxygen-rich 3D hierarchical porous MXene prepared by Zn powder reduction for flexible supercapacitors

Ti3C2Tx MXene is highly compelling as an energy storage material, but 2D MXene sheets experience significant stacking due to hydrogen bonding and van der Waals forces. This blocks active sites and impedes fast electrolyte ion transport. The pseudocapacitance of MXene materials is highly reliant on their terminal groups. Therefore, an effective strategy was designed herein to prepare an oxygen-rich 3D hierarchical porous MXene (P-OR-Ti3C2Tx). First, Zn powder was used as a template to construct three-dimensional hierarchical porous structures that spanned the microporous, mesoporous, and macroporous scales. Second, Zn powder was used as a metal reducing agent in a reaction at 500 °C to eliminate most −F terminal groups on the MXene. Then, a subsequent acid washing step was used to introduce numerous −O terminal groups. The energy storage process of the prepared MXene was investigated by in situ Raman. More redox active sites (−O terminal groups) are exposed by the constructed oxygen-rich 3D hierarchical porous MXene structure, which also provides a shorter pathway for electrolyte ion transport. P-OR-Ti3C2Tx displays superb rate performance (88.19 % retention at 100Ag−1) and ultra-high capacitance (676.7F/g at 2 mV/s and 698.7Fg−1 at 1 Ag−1) when used as a supercapacitor electrode. Moreover, a symmetric flexible supercapacitor device prepared using P-OR-Ti3C2Tx and carbon cloth achieves a superb energy density of 32.8Whkg−1 at a power density of 236.5Wkg−1. This study offers insight into the design of MXenes that exhibit both high capacity and excellent rate performance.

In situ decoration of 0D-nickel boride on 2D-vanadium MXene composites: An advanced electrode material for high energy density supercapacitors

Vanadium carbide-MXene (V2CTx) is considered a rising star among 2D materials and is an ideal electrode material for energy storage due to its unique features. However, oxidation and layer restacking can impair specific capacity (Cs) and cycling performance. Considering this challenge, we have developed a composite material consisting of amorphous nickel boride (NixB NPs) and V2CTx. To prevent oxidation and restacking of the layers and to improve the performance of the supercapacitor, NixB was decorated between the gaps and the surface. The V2CTx and its composites were prepared by simple etching and direct liquid-phase methods. Under the optimized conditions, the NixB/V2CTx modified nickel foam exhibited an improved Cs value of 705.9 C g−1 and a rate capability of 53.8 % at a current density of 10 A g−1; the excellent cycling stability was 120.5 % after 10,000 cycles at 10 A g−1 in 3 M KOH. The improved Cs values, shortened ion diffusion paths, swift electron transfer, and excellent cycling stability of the composites are due to the V2CTx layers surface entrapped/gaps filled by the NixB NPs. For practical application, an asymmetric device with NixB/V2CTx and reduced graphene oxide (rGO) as positive and negative electrodes was fabricated. The NixB/V2CTx//rGO device achieved a maximum energy density of 50.22 Wh kg−1 at 800 W kg−1 and 26 Wh kg−1 at 16000 W kg−1. The capacity retention was 89.98 % and the Coulombic efficiency was 99.9 % after 20,000 continuous cycles at 8 A g−1. These results emphasized that the developed 0D/2D NixB/V2CTx electrode materials with novel composite architecture are suitable for advanced energy storage applications.

Effects of pore characteristics on CO2 adsorption performance of coal slime with different metamorphic degrees

With the rapid development of Carbon Capture, Utilization and Storage (CCUS) technology, it is necessary to explore the feasibility of coal slime as a porous carbon material for CO2 capture. In this paper, scanning electron microscopy (SEM) was used to observe the morphological characteristics of coal slime samples with different metamorphic degrees, and the pore structure of coal slime was explored by low temperature N2 adsorption and low-pressure CO2 adsorption experiments. The pore distribution characteristics were analyzed, and the adsorption law of different metamorphic degrees were summarized through CO2 isothermal adsorption experiments. The results showed that: The specific surface area (SSA) and pore volume (PV) of the mesopores of the coal slime exhibited a U-shaped distribution with coal rank, and are much smaller than that of its micropores. Micropores less than 2 nm are the main adsorption space of coal slime, its PV accounted for 59%, 60%, 71%, and SSA accounted for 92%, 93%, 95%, obviously, which are dominant at all stages. The linear correlation fitting coefficients R2 between the limiting adsorbed amount a of CO2 and the micropores PV and the SSA were up to 0.830 and 0.887, respectively. The coal slime has good adsorption performance for CO2. Based on the Langmuir model to fit the limit adsorption amount, a-value can reach 41.774 cm3 g−1, 32.072 cm3 g−1, 38.457 cm3 g−1 at 303 K with the increase of Rmax. Studying the impact of coal slime on CO2 adsorption performance provides a theoretical basis for the subsequent preparation of energy storage materials and is of great significance for the safe, efficient and economic capture and sequestration of CO2, to alleviate the serious situation of the environment and realizing the dual-carbon goal.

Porous Carbon Electrode from Starch Soluble for Realizing High‐Performance Supercapacitor

AbstractOrganic potassium salts are the promising green activators for synthesizing porous carbon materials for energy storage. Herein, we report the synthesis of hierarchical porous carbon material derived from the mixture of soluble starch and ethylenediaminetetraacetic acid dipotassium salt dihydrate (EDTA‐2K) via carbonization and activation strategy. The sample is used as supercapacitors electrode, which exhibits superior mass specific capacitance (307.3 F g−1 at 1 A g−1), good rate performance (255.0 F g−1 at 10 A g−1), and excellent stability (retaining 83 % after 15000 cycles). This enhanced electrode performance is mainly due to the high specific surface area, the heteroatom co‐doping providing pseudo‐capacitance and the improved electronic conductivity. In addition, the asymmetric supercapacitor device shows a high energy density of 15 Wh kg−1 at the power density of 800 W kg−1 and capacitance retention of 90 % after 12000 cycles.

A dual functional Co3O4 thin film with remarkable electrochromic and energy storage performance in the electrolytes of choline chloride and urea

The electrolyte layer plays an important role in ion transport in electrochromic devices, and the optimized preparation of efficient electrolytes can positively affect the conduction process on the electrode surface and at the electrode-electrolyte interface.In this study, we start from a green perspective while improving the performance. Combined with typical eutectic solvents: choline chloride and urea materials. A suitable ratio favorable for the reaction of Co3O4 film is explored and combined with sodium hydroxide, a traditional electrolyte, to enhance the electrochromic performance.The electrochromic and electrochemical properties of Co3O4 films prepared via the sol-gel method in the novel electrolyte were then evaluated. The results show that the performance has been greatly improved, the transmittance rate is 2.5 times higher than the original, the coloration efficiency is 5.8 times higher than the original, and it is more stable and has higher charging and discharging efficiency. This presents a promising avenue for the advancement of oxide films as bifunctional materials for electrochromism and energy storage. The newly developed electrolyte may prove beneficial in enhancing the performance and stability of electrochromic devices through the use of alkaline electrolytes.

Phosphonitrile based porous organic polymers as effective flame-retardant electrolytes for lithium battery

Developing electrolytes with flame-retardant properties become the critical factor in making high safety lithium batteries. As phosphonitrile-based compounds are a kind of typical flame-retardant materials, herein, taking phosphonitrile-based aldehyde as the basic organic building blocks, two porous organic polymers (POPs) named as PVPH and PVPH-CO2H were successfully fabricated after solvothermal reaction with 1,3-diaminobenzene (MPD) and 5-carboxy-1,3-diaminobenzene (MPD-CO2H), respectively for electrolytes of lithium batteries. Studies revealed that both of the phosphonitrile-based POPs demonstrate good thermal stability and excellent flame-retardant properties, suggesting they are promising flame-retardant electrolytes for the application in battery. Battery performance investigations revealed that both of them, especially PVPH-CO2H, show good performance after assembling them into lithium batteries. This study paves the way to improve battery safety performance by employing the flame-retardant phosphonitrile-based porous polymers as effective electrolytes. Moreover, it also broadens the application of flame-retardant materials in energy storage materials.

Novel design of Sn4P3@NxC electrodes and their electrochemical properties

Tin phosphide (SnxPy) is recognized as one of the most promising anode materials for lithium-ion batteries due to its exceptionally high theoretical capacity. However, its application is hampered by significant volume expansion during charge-discharge cycles and inferior electrical conductivity. Proper structural design plays a pivotal role in addressing these challenges, paving the way for high-performance anode materials. This study introduces a nitrogen-doped carbon-coated Sn4P3 nanosphere with a core-shell structure, employing dopamine as the nitrogen source. This innovative approach, utilizing template removal and solid-phase phosphorization, results in both the core and shell acting as active materials, thereby enhancing the volumetric energy density of the electrode. The internal voids within the shell layer mitigate volume expansion during charge-discharge cycles, while the presence of the nitrogen-doped carbon layer maintains the material's stability throughout cycling and improves its electrical conductivity. Electrochemical performance tests confirm this material's outstanding energy storage capability, with an initial Coulombic efficiency reaching up to 73.6 %. Furthermore, it maintains a stable capacity of 585 mAh g−1 after 1200 cycles at a current density of 2 A g−1. This research offers a design paradigm for developing novel energy storage materials.

Experimental study on supercooling performance optimization of sodium acetate trihydrate phase change energy storage materials

In response to the pressing demands for sustainable energy, the development of efficient energy storage materials and technologies has emerged as a focal point in contemporary research. Sodium acetate trihydrate (CH3COONa·3H2O, SAT), recognized for its potential as a mid-to-low temperature phase change material (PCM) in energy storage systems, encounters significant limitations due to its substantial supercooling effect and inferior thermal conductivity. Traditional approaches to enhance SAT's thermal performance often involve costly additives, which hinder their adoption on an industrial scale. This study introduces SAT as a base compound, and through a fusion blending method, binary eutectic hydrate salt composites (CPCMs) are synthesized with either sodium sulfate decahydrate (Na2SO4·10H2O, SSD) or disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O, DHPD) in varying ratios. The results demonstrate that the prepared eutectic hydrates effectively reduce the supercooling degree of pure SAT from above 35 °C to below 10 °C, with the SAT/SSD-5/5 composition exhibiting the lowest supercooling at 3.17 °C. Notably, these eutectic blends possess appreciable latent heat capacities, with SAT/SSD-9/1 delivering 196.18 J/g, and exhibit improved thermal conductivity, as seen in SAT/SSD-3/7 with a coefficient of 0.8925 W/(m·K). Furthermore, the SAT-based eutectic hydrates are devoid of expensive additives, facile to manufacture, and applicable over a broad temperature range (20–60 °C), making them highly suitable for large-scale commercial applications.

Trimetallic-doped carbon nitride achieves chondroitin sulfate degradation via a free radical degradation strategy

Traditional Fenton principles for degrading polysaccharides, including chondroitin sulfate (CS), are fraught with limitations, such as strict pH-dependence, higher temperature requirements, desulfurization, and environmentally perilous. In this study, an effective Fenton-like system comprising trimetallic-doped carbon nitride material (tri-CN) with hydrogen-bonded melamine-cyanuric acid (MCA) supramolecular aggregates as its basic skeleton was engineered to overcome the challenges of traditional methods. Detailed material characterizations revealed that, compared to monometallic-doped or bimetallic-doped counterparts, tri-CN offered a larger surface area, higher porosity, and increased metal loading, thereby enhancing reactant accessibility and polysaccharide degradation efficiency. The characterization and activity assessment of the degraded polysaccharide revealed structurally intact products without significant desulfurization, indicating the effectiveness of the designed approach. Moreover, the degraded chondroitin sulfate CS3 catalyzed by tri-CN, exhibited promising antioxidant activity and anti-CRISPR potential. The results elucidated that the high-valent iron species in the material served as primary active sites, catalyzing the cleavage of hydrogen peroxide to generate hydroxyl radicals that subsequently attacked CS chains, leading to their fragmentation. Hence, the designed material can be efficiently applied to polysaccharide degradation, but not limited to photocatalysis, electrocatalysis, sensor, energy storage materials, and wastewater treatment.

Theoretical exploration of AlB2 monolayer with high energy storage properties in the field of ion battery materials

The rapid development of electric vehicles has promoted researchers to explore the field of high-capacity batteries. Two-dimensional (2D) materials have been proven to have ultra-high storage capacity due to their unique structural advantages. A first-principles approach was applied here to verify the feasibility of the novel AlB2 monolayer as an anode material with ultra-high storage capacity for Li/Na-ion batteries. The Li capacity of AlB2 monolayer is up to 3308.6 mAh/g. Meanwhile, the Na capacity up to 1654.3 mAh/g. It is worth noting that the diffusion barrier of the monolayer is extremely low (Li: 0.50 eV; Na 0.26 eV). The results show that AlB2 monolayer is a kind of anode material for high energy storage, which provides a new choice for the development of long-life battery.

High energy density picoliter-scale zinc-air microbatteries for colloidal robotics.

The recent interest in microscopic autonomous systems, including microrobots, colloidal state machines, and smart dust, has created a need for microscale energy storage and harvesting. However, macroscopic materials for energy storage have noted incompatibilities with microfabrication techniques, creating substantial challenges to realizing microscale energy systems. Here, we photolithographically patterned a microscale zinc/platinum/SU-8 system to generate the highest energy density microbattery at the picoliter (10-12 liter) scale. The device scavenges ambient or solution-dissolved oxygen for a zinc oxidation reaction, achieving an energy density ranging from 760 to 1070 watt-hours per liter at scales below 100 micrometers lateral and 2 micrometers thickness in size. The parallel nature of photolithography processes allows 10,000 devices per wafer to be released into solution as colloids with energy stored on board. Within a volume of only 2 picoliters each, these primary microbatteries can deliver open circuit voltages of 1.05 ± 0.12 volts, with total energies ranging from 5.5 ± 0.3 to 7.7 ± 1.0 microjoules and a maximum power near 2.7 nanowatts. We demonstrated that such systems can reliably power a micrometer-sized memristor circuit, providing access to nonvolatile memory. We also cycled power to drive the reversible bending of microscale bimorph actuators at 0.05 hertz for mechanical functions of colloidal robots. Additional capabilities, such as powering two distinct nanosensor types and a clock circuit, were also demonstrated. The high energy density, low volume, and simple configuration promise the mass fabrication and adoption of such picoliter zinc-air batteries for micrometer-scale, colloidal robotics with autonomous functions.

Flexible energy storage device fabricated by electrochromic smart copolymer based on thienothiophene-triphenyamine and EDOT

Sustainable energy storage materials are of increasing importance for new energy technologies to produce more intelligent, lighter, thinner and multifunctional power systems. In this study, copolymers of N-(4-(4-thieno[3,2-b]thiophene-3-ylphenyl)phenyl)-N-phenylbenzenamine (TTpTPA) and 3,4-ethylenedioxythiophene (EDOT) were synthesized electrochemically starting from different molar ratios of TTpTPA(T) and EDOT(E) (nT:nE). The copolymers obtained on the ITO surface, i.e. P(T10-1E), P(T5-1E), P(T5-2E), P(T1-1E), were directly used to design electrochromic energy storage devices (ECESDs). Electrochemical characterizations suggested that the copolymerization improved the capacitances of PTTpTPA and PEDOT up to the highest value of 21 mF cm−2 with the copolymer P(T1-1E). It exhibited a color change from purple to blue during charging and discharging processes. Additionally, P(T5-2E) displayed a remarkable multicolor change as a color cartel, i.e. red, yellow, green, gray and blue, during the oxidation with a high color efficiency of 161 cm2C−1. Finally, the flexible symmetric device prototype of P(T1-1E) possessed a good practical application for next generation energy storage devices with its high energy and high-power densities.

Optimizing Energy Storage Performance in Polymer Dielectrics through Dual Strategies: Constructing “Peaked” Barrieras and Enhancing Carrier Scattering

AbstractDielectric capacitors play a pivotal role in the advancement of electric power systems and emerging energy technologies. However, the deterioration of dielectric performance in energy storage materials at elevated temperatures represents a significant challenge. In this study, organic electron‐scattering agents into polyetherimide (PEI) are introduced, creating a “peaked barrier” to impede charge carrier transport. By doping PEI with an ultralow volume fraction (0.8%) of the organic molecule filler 4‐(dimethylamino)phenylboronic acid (4‐NB), the electron‐repelling nature of 4‐NB is leveraged in order to regulate charge carrier injection and transport in a synergistic manner. Consequently, the discharged energy density of the PEI composite material increases to 7.93 J cm−3 (720 kV mm−1) at 30 °C. At 150 °C, the discharged energy density increases to 5.21 J cm−3 (580 kV mm−1). In both cases, the charge and discharge efficiencies are maintained at 90%. It is noteworthy that the prepared PEI composite material also exhibits excellent charge dissipation characteristics, maintaining stable charge and discharge efficiency even after 50 000 charge–discharge cycles. In summary, the study's design concept systematically optimizes the processes of charge carrier injection, transport, and dissipation. This approach offers a novel perspective for the development of dielectrics that are suitable for long‐term energy storage.

Thermal cycling damage of silica refractories for high-temperature thermal energy storage (HT-TES) – Can it be healed?

Silica refractories are promising materials for high-temperature thermal energy storage (HT-TES), because they exhibit excellent thermal cycling properties, unless cooled below a critical temperature (usually assumed to be 600 °C). When cooling down to room temperature severe damage can occur, which can be conveniently monitored via the impulse excitation technique (IET). This damage is most severe when the cycling maximum temperature is low. The question is whether this damage can be healed again. In this short contribution we show that severe damage in silica refractories, caused by heating from room temperature to 300 °C and back again to room temperature, can indeed be healed by thermal cycling to 1300 °C. The healed material is actually better than the pristine material.

Capric-lauric & capric-palmitic/modified bentonite composite as phase change materials for thermal energy storage

This paper proposes a new double layer structure shape-stabilized thermal energy storage wallboard (TESW), by employing microwave radiation modified bentonite (Bm) to stabilize capric acid-lauric acid (CA-LA) and capric acid-palmitic acid (CA-PA) as major components of internal and external wallboard. Leakage test showed that CA-LA/Bm and CA-PA/Bm had good morphological stability. The chemical compatibility, phase change behaviors, and microstructure of CA-LA/Bm and CA-PA/Bm were analyzed. The maximal loading capacities of CA-LA/Bm and CA-PA/Bm can be reached 45 % and 50 %, respectively. In addition, the mechanical and thermal performance of CA-LA/Bm and CA-PA/Bm-based thermal energy storage concrete (CL&CP/Bm-TESC) was systematically studied. The Digital Image Correlation (DIC) technology was used to collect and analyze the speckle images of CL&CP/Bm-TESC20 before and after 100 cycles of phase change, determining the evolution of principal strains during the deformation and failure processes. It is worth noting that the numerical simulation results of the designed double layer structure shape-stabilized CA-LA&CA-PA/Bm-based thermal energy storage wallboard (CL&CP/Bm-TESW) show better temperature adjusting performance. These results demonstrate that the prepared composite of CA-LA/Bm and CA-PA/Bm has potential application in the field of thermal energy storage.

In-Situ Sulfuration of CoAl Metal-Organic Framework for Enhanced Supercapacitor Properties.

Designing efficient electrode materials is necessary for supercapacitors but remains highly challenging. Herein, cobalt sulfide with crystalline/amorphous heterophase (denoted as Co(Al)S) derived from an Al metal-organic framework was constructed by ion exchange/acid etching and subsequent sulfidation strategy. It was found that rational sulfidation by adjusting the sulfur source concentration to a suitable level was favorable to form a 3D nanosheet-interconnected network architecture with a large specific surface area, which promoted ion/electron transport and charge separation. Benefiting from the features of the unique network structure and heterophase accompanied by aluminum, nitrogen and carbon coordinated in amorphous phase, the optimal Co(Al)S(10) exhibited a high specific capacity (1791.8 C g-1 at 1 A g-1), an outstanding rate capability and an excellent cycling stability. Furthermore, the as-assembled Co(Al)S//AC device afforded an energy density of 72.3 Wh kg-1 at a power density of 750 W kg-1, verifying that the Co(Al)S was a promising material for energy storage devices. The developed scheme is expected to promote the application of MOF-derived electrode materials in electrochemical energy storage and conversion fields.

Thermal conductivity enhancement of polyethylene glycol/NF composite as stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG) has the advantages of large latent heat of phase transition, a wide range of phase transition, and cheap price, but the application of PEG in the latent thermal energy storage (TES) systems is hindered due to its lower heat transfer rate and leakage. Porous metal foam has excellent thermal conductivity and high strength, which can effectively improve the problems of PEG. In this study, PEG/nickel foam (NF) composite phase change materials (PCM) were prepared by vacuum molten impregnation method using NF as substrate. It was found that PEG had good compatibility with NF, and the highest impregnation rate of PEG6000/NF reached 85.73 %. The thermal conductivity of PEG2000/NF can be increased to 1.58 1.58 W·m−1 K−1, nearly 4 times larger than that of pure PEG. The phase change temperature range of the composite PCM is 51–63 °C, and the phase change enthalpy is 67.8–126.3 J·g−1. Furthermore, the PEG/NF composite demonstrated outstanding photothermal conversion properties and high thermal stability, which can be widely used in the field of building temperature control and device heat dissipation.

The impact of zinc ions on electrode material for energy storage in solvothermal-synthesised graphene-zinc oxide nanocomposites

ABSTRACT The study examines the impact of zinc ions on energy storage in solvothermal-synthesised graphene-zinc oxide nanocomposites. In recent years, there has been extensive research focus on graphene and metal oxides, particularly in heterostructures and composites. These materials have a broad range of applications, like energy storage. Faradaic processes were shown by the observation of redox peaks in the CV analysis of a three-electrode system. The estimated specific capacitances of graphene at scan rates of (1, 50, and 100) mVS−1 were (1250, 562.5, and 390.6) Fg−1. The G-ZnO (2 w%) and G-ZnO (3 w%) gave the specific capacitance of (1354, 750, and 520) Fg−1 and (1422, 818, and 568) Fg−1 at the same scan rates of 1, 50, and 100 mV/s. Applying a potential to the material reveals its pseudo-capacitive properties. The XRD results for G-ZnO (2 w%) and G-ZnO (3 w%) show diffraction peaks at 2θ = 20.56°, 32.95°, 40.69°, 47.41°, 59.02°, and 69.04°, which correspond to the diffraction planes 011, 100, 101, 102, 110, and 200, respectively.

(Invited) Probing Electrochemical Interfaces in Catalytic and Energy Materials and Process Using Operando Soft X-Ray Spectroscopy

Advanced energy technology arises from the understanding in fundamental science, thus rest in large on in-situ/operando characterization tools for observing the physical and chemical interfacial processes. Synchrotron based X-ray spectroscopic techniques offers unique characterization in many important energy materials of energy conversion, energy storage and catalysis in regards to the functionality, complexity of material architecture, chemistry and interactions among constituents within. However, it is challenging to reveal the real mechanism of the chemical processes.In the operando soft X-ray spectroscopy characterization of interfacial phenomena in energy materials and devices, it has been found that the microstructure and composition of materials as well as the microstructure evolution process have a great influence on performances in a variety of fields, e.g., energy conversion and energy storage materials, chemical and catalytic processes. This presentation will show how to best use the in-situ/operando soft X-ray spectroscopy characterization techniques, including soft x-ray absorption spectroscopy (XAS) and resonant inelastic soft X-ray scattering (RIXS) to investigate the real electrochemical mechanism during the operation. The experimental results show how in-situ/operando soft X-ray spectra characterization techniques uncover the phase conversion, chemical and environmental change of elements and other very important information of solid/gas and solid/liquid interfaces in real time, thus further enhance the understanding of real reaction mechanism.