Redox-active supercapacitor electrode from two-monomer-connected precursor (Pyrrole: Anthraquinonedisulfonic acid: Pyrrole) and sulfonated multi-walled carbon nanotube

A drive towards a bi-linker strategy: tailoring MOF efficiency for advanced battery-supercapacitor hybrid devices

Metal-organic frameworks (MOFs) have emerged as promising materials for supercapacitor applications; however, challenges such as limited conductivity, stability, and rate capability hinder their practical implementation. Despite extensive efforts, including hybridization and bimetallic strategies, a significant performance gap remains. In this work, we introduce a drive towards a bi-linker approach to engineer nickel-based MOFs, systematically varying the ratio of pyridine-2,6-dicarboxylic acid and pyromellitic acid (linkers) to tailor their morphological evolution and electrochemical properties. This strategic modulation was found to directly influence electrochemical behavior. Among the synthesized materials, X2 (PDC0.75PMA0.25-MOF) exhibited the most favorable characteristics, achieving low ESR (0.72 Ω) and electrochemical efficiency (demonstrating 694.3 C g-1 at 3 mV s-1 and 576.6 C g-1 at 0.6 A g-1) in a three-electrode cell configuration. To further evaluate its real device potential, a battery-supercapacitor hybrid device (X2//AC) was fabricated, demonstrating a remarkable specific capacity of 298.1 C g-1 at 1.4 A g-1, a high specific energy of 70.3 W h kg-1 at a power density of 1190 W kg-1, and good cycling stability (98.5% retention after 5000 cycles). These findings open a new pathway for future research on bi-linker-driven MOF design, providing a novel strategy for enhancing electrochemical performance and advancing next-generation energy storage applications.

Advances in Graphene-Transition Metal Selenides Hybrid Materials for High-Performance Supercapacitors: A Review

Supercapacitors have attracted significant attention as energy storage devices due to their high power density, rapid charge-discharge capability, and long cycle life. Their performance is primarily influenced by electrode materials, electrolytes, and operational voltage windows. Among these, the development of advanced electrode materials is crucial for enhancing energy density, specific capacitance, and cyclic stability. This review focuses on recent advancements in graphene-based hybrid materials, particularly their integration with transition metal selenides (TMSs) for supercapacitor applications. Combining graphene and its derivatives with TMSs, which possess multiple oxidation states and high theoretical capacitance, results in hybrids with superior electrochemical performance. Studies show that these materials achieve higher specific capacitance, energy density, and power density compared to graphene composites with carbides, nitrides, phosphides, and oxides. Key findings include synthesis strategies, structural modifications, and electrochemical properties of graphene-TMS hybrids. Notably, these hybrids have demonstrated specific capacitances exceeding 3105 F/g at 1 A/g, power densities up to 5597.77 W/kg, and energy densities reaching 126.3 Wh/kg, making them highly promising for next-generation supercapacitors. This review critically evaluates the current state-of-the-art, explores the synergistic effects between graphene and TMSs, such as improved charge transfer kinetics and structural stability, and identifies challenges and future directions in graphene-TMS hybrid supercapacitors.

Atomic Layer Deposition-A Versatile Toolbox for Designing/Engineering Electrodes for Advanced Supercapacitors

Atomic layer deposition (ALD) has become the most widely used thin-film deposition technique in various fields due to its unique advantages, such as self-terminating growth, precise thickness control, and excellent deposition quality. In the energy storage domain, ALD has shown great potential for supercapacitors (SCs) by enabling the construction and surface engineering of novel electrode materials. This review aims to present a comprehensive outlook on the development, achievements, and design of advanced electrodes involving the application of ALD for realizing high-performance SCs to date, as organized in several sections of this paper. Specifically, this review focuses on understanding the influence of ALD parameters on the electrochemical performance and discusses the ALD of nanostructured electrochemically active electrode materials on various templates for SCs. It examines the influence of ALD parameters on electrochemical performance and highlights ALD's role in passivating electrodes and creating 3D nanoarchitectures. The relationship between synthesis procedures and SC properties is analyzed to guide future research in preparing materials for various applications. Finally, it is concluded by suggesting the directions and scope of future research and development to further leverage the unique advantages of ALD for fabricating new materials and harness the unexplored opportunities in the fabrication of advanced-generation SCs.

Hierarchical Hollow Carbon Particles with Encapsulation of Carbon Nanotubes for High Performance Supercapacitors

A novel and sustainable carbon-based material, referred to as hollow porous carbon particles encapsulating multi-wall carbon nanotubes (MWCNTs) (CNTs@HPC), is synthesized for use in supercapacitors. The synthesis process involves utilizing LTA zeolite as a rigid template and dopamine hydrochloride (DA) as the carbon source, along with catalytic decomposition of methane (CDM) to simultaneously produce MWCNTs and COx -free H2 . The findings reveal a distinctive hierarchical porous structure, comprising macropores, mesopores, and micropores, resulting in a total specific surface area (SSA) of 913 m2  g-1 . The optimal CNTs@HPC demonstrates a specific capacitance of 306 F g-1 at a current density of 1 A g-1 . Moreover, this material demonstrates an electric double-layer capacitor (EDLC) that surpasses conventional capabilities by exhibiting additional pseudocapacitance characteristics. These properties are attributed to redox reactions facilitated by the increased charge density resulting from the attraction of ions to nickel oxides, which is made possible by the material's enhanced hydrophilicity. The heightened hydrophilicity can be attributed to the presence of residual silicon-aluminum elements in CNTs@HPC, a direct outcome of the unique synthesis approach involving nickel phyllosilicate in CDM. As a result of this synthesis strategy, the material possesses excellent conductivity, enabling rapid transportation of electrolyte ions and delivering outstanding capacitive performance.

Valorization of Biomass-Derived Polymers to Functional Biochar Materials for Supercapacitor Applications via Pyrolysis: Advances and Perspectives

Polymers from biomass waste including plant/forest waste, biological industrial process waste, municipal solid waste, algae, and livestock are potential sources for renewable and sustainable resources. Converting biomass-derived polymers to functional biochar materials via pyrolysis is a mature and promising approach as these products can be widely utilized in many areas such as carbon sequestration, power production, environmental remediation, and energy storage. With abundant sources, low cost, and special features, the biochar derived from biological polymeric substances exhibits great potential to be an alternative electrode material of high-performance supercapacitors. To extend this scope of application, synthesis of high-quality biochar will be a key issue. This work systematically reviews the char formation mechanisms and technologies from polymeric substances in biomass waste and introduces energy storage mechanisms of supercapacitors to provide overall insight into the biological polymer-based char material for electrochemical energy storage. Aiming to enhance the capacitance of biochar-derived supercapacitor, recent progress in biochar modification approaches including surface activation, doping, and recombination is also summarized. This review can provide guidance for valorizing biomass waste to functional biochar materials for supercapacitor to meet future needs.

Rational Design of Bifunctional Microporous Organic Polymers Containing Anthracene and Triphenylamine Units for Energy Storage and Biological Applications

In this study, we synthesized two conjugated microporous polymers (CMPs), An-Ph-TPA and An-Ph-Py CMPs, using the Suzuki cross-coupling reaction. These CMPs are organic polymers with p-conjugated skeletons and persistent micro-porosity and contain anthracene (An) moieties linked to triphenylamine (TPA) and pyrene (Py) units. We characterized the chemical structures, porosities, thermal stabilities, and morphologies of the newly synthesized An-CMPs using spectroscopic, microscopic, and N₂ adsorption/desorption isotherm techniques. Our results from thermogravimetric analysis (TGA) showed that the An-Ph-TPA CMP displayed better thermal stability with T_d10 = 467 °C and char yield of 57 wt% compared to the An-Ph-Py CMP with T_d10 = 355 °C and char yield of 54 wt%. Furthermore, we evaluated the electrochemical performance of the An-linked CMPs and found that the An-Ph-TPA CMP had a higher capacitance of 116 F g^-1 and better capacitance stability of 97% over 5000 cycles at 10 A g^-1. In addition, we assessed the biocompatibility and cytotoxicity of An-linked CMPs using the MTT assay and a live/dead cell viability assay and observed that they were non-toxic and biocompatible with high cell viability values after 24 or 48 h of incubation. These findings suggest that the An-based CMPs synthesized in this study have potential applications in electrochemical testing and the biological field.

Carbonized Aminal-Linked Porous Organic Polymers Containing Pyrene and Triazine Units for Gas Uptake and Energy Storage

Porous organic polymers (POPs) have plenteous exciting features due to their attractive combination of microporosity with π-conjugation. Nevertheless, electrodes based on their pristine forms suffer from severe poverty of electrical conductivity, precluding their employment within electrochemical appliances. The electrical conductivity of POPs may be significantly improved and their porosity properties could be further customized by direct carbonization. In this study, we successfully prepared a microporous carbon material (Py-PDT POP-600) by the carbonization of Py-PDT POP, which was designed using a condensation reaction between 6,6'-(1,4-phenylene)bis(1,3,5-triazine-2,4-diamine) (PDA-4NH₂) and 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (Py-Ph-4CHO) in the presence of dimethyl sulfoxide (DMSO) as a solvent. The obtained Py-PDT POP-600 with a high nitrogen content had a high surface area (up to 314 m² g^-1), high pore volume, and good thermal stability based on N₂ adsorption/desorption data and a thermogravimetric analysis (TGA). Owing to the good surface area, the as-prepared Py-PDT POP-600 showed excellent performance in CO₂ uptake (2.7 mmol g^-1 at 298 K) and a high specific capacitance of 550 F g^-1 at 0.5 A g^-1 compared with the pristine Py-PDT POP (0.24 mmol g^-1 and 28 F g^-1).

Conjugated Microporous Polymers Based on Ferrocene Units as Highly Efficient Electrodes for Energy Storage

This work describes the facile designing of three conjugated microporous polymers incorporated based on the ferrocene (FC) unit with 1,4-bis(4,6-diamino-s-triazin-2-yl)benzene (PDAT), tris(4-aminophenyl)amine (TPA-NH₂), and tetrakis(4-aminophenyl)ethane (TPE-NH₂) to form PDAT-FC, TPA-FC, and TPE-FC CMPs from Schiff base reaction of 1,1'-diacetylferrocene monomer with these three aryl amines, respectively, for efficient supercapacitor electrodes. PDAT-FC and TPA-FC CMPs samples featured higher surface area values of approximately 502 and 701 m² g^-1, in addition to their possession of both micropores and mesopores. In particular, the TPA-FC CMP electrode achieved more extended discharge time compared with the other two FC CMPs, demonstrating good capacitive performance with a specific capacitance of 129 F g^-1 and capacitance retention value of 96% next 5000 cycles. This feature of TPA-FC CMP is attributed to the presence of redox-active triphenylamine and ferrocene units in its backbone, in addition to a high surface area and good porosity that facilitates the redox process and provides rapid kinetics.

A short review article on conjugated polymers

This article provides a brief review of conjugated polymers and the various typical polymerization reactions exploited by the community to synthesise different conjugated polyelectrolytes with varied conjugated backbone systems. We further discuss with detailed emphasises the mechanism involved such as photo-induced electron transfer, resonance energy transfer, and intra-molecular charge transfer in the detection or sensing of various analytes. Owing to their excellent photo-physical properties, facile synthesis, ease of functionalization, good biocompatibility, optical stability, high quantum yield, and strong fluorescence emission. Conjugated polymers have been explored for wide applications such as chemical and biological sensors, drug delivery and drug screening, cancer therapeutics and imaging. As such we believe it will be a timely review article for the community.

Intermolecular interactions of an isoindigo-based organic semiconductor with various crosslinkers through hydrogen bonding

The effects of crosslinkers, functioning via hydrogen bonding, on controlling the arrangement of molecules were investigated. The hole mobility of hydrogen-bonded organic materials displaying long-range order was significantly enhanced.