Search Results (260)

Zeolitic imidazolate framework-8 (ZIF-8) has emerged as a material for electrochemical energy conversion, serving dual primary roles in fuel cell technologies: (i) as an electrocatalyst precursor for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) through pyrolysis-derived N-doped porous carbons and metal–nitrogen–carbon (M–N–C) structures, and (ii) as a membrane component that enhances proton conductivity via imidazole-mediated Grotthuss hopping while suppressing fuel crossover through molecular sieving. This comprehensive review systematically evaluates ZIF-8 performance across multiple fuel cell types, including primarily proton exchange membrane fuel cells (PEMFCs), as well as direct methanol fuel cells (DMFCs), anion exchange membrane fuel cells (AEMFCs), and microbial fuel cells (MFCs), while also covering related electrochemical applications such as zinc–air batteries, supercapacitors, and water splitting devices, where ZIF-8-derived materials demonstrate improved catalytic activity. The review examines structure–performance relationships, highlighting strategies such as heteroatom doping, bimetallic synergy, hierarchical porosity engineering, and polymer composite fabrication that have enabled ZIF-8-based catalysts to achieve ORR half-wave potentials and PEMFC power densities, rivaling commercial Pt/C systems. ZIF-8 composite membranes demonstrate proton conductivities in polybenzimidazole systems and effective methanol blocking. Despite improved progress, challenges persist regarding long-term stability, scalable synthesis, and degradation mechanism understanding. This review critically analyzes recent advances, identifies performance-limiting factors across applications, and outlines future research directions for developing commercially viable ZIF-8-based electrochemical technologies. Full article

Rice husk (RH) is a renewable siliceous lignocellulosic waste providing a unique, greener and less toxic alternative to conventional synthetic polymeric precursors in the production of carbon-based materials for biomedical applications. In this work we studied the porous structure of RH-lignin-based activated carbon produced in the form of honeycomb carbon monoliths and assessed their potential as hemoadsorbents for blood purification in the treatment of patients with serious medical conditions, such as kidney failure and sepsis. To determine their clinical suitability for such an application, the hemocompatibility and cytotoxicity of the monoliths were investigated using the standard ISO guidelines. The monoliths did not cause any changes in the cell viability or cell lysis. High micro/mesoporosity and surface chemistry of the initial monolith-C, N- and P-doped nanostructured carbon honeycomb monoliths were established by low-temperature nitrogen adsorption (LTNA) studies, mercury porosimetry data (MIP), SEM/EDS analysis and FT-IR spectroscopy. The micro-mesoporous, activated carbon-based filtration/adsorbent prototype devices, in the form of three-dimensional (3D) carbon matrix, functionalized with ion-exchange amino- and phosphate groups and encased in polyolefin heat shrink cable sleeve, have been developed with the capacity to remove protein-bound uremic toxins (PBUTs), such us PCS and IS, as well as inflammatory cytokines (IL-6 and IL-8) from human plasma in a flowing model system. The ammoxidized monolith-N, derived from the monolith-C, had the highest removal efficiency (40.05% for PCS, and 28.4% for IL-6). By contrast, phosphorylated monolith-P demonstrated the highest removal efficiency (54.62% for IS, and 54.4% for IL-8), whilst the monolith-C has the lowest removal efficiency for these adsorbates. These results do not correlate with the LTNA and MIP study results, suggesting that the interaction of surface chemical functional groups with the solutes play key roles in the adsorption mechanism. The ion-exchange mechanism of PBUTs and inflammatory cytokine chemisorption by the monoliths, modified with surface N- and P-containing functional groups, has been proposed. Full article

The transition toward a sustainable hydrogen economy demands cost-effective, durable, and highly active catalysts that span the entire H₂ value chain from green production through storage and transport to end-use conversion. Carbon-based catalytic materials have emerged as a uniquely versatile platform, offering tunable electronic structure, abundant defect- and edge-derived active sites, hierarchical porosity, chemical robustness, and compatibility with both metal-free and single-atom architectures. This review provides a comprehensive overview of advanced carbon-based catalysts designed for the hydrogen economy. We begin with the fundamentals of heteroatom doping, defect and curvature engineering, and M–N₄/M–N₃ coordination environments that govern binding of hydrogen-relevant intermediates (ΔG_H*, ΔG_OH*, ΔG_O*). Three application pillars are then systematically examined: (i) hydrogen production through HER and OER across PEMWE, AEMWE, AWE, and SOEC platforms, including emerging seawater and biomass-/waste-coupled electrolysis; (ii) hydrogen storage and chemical carriers, encompassing physisorption on porous carbons and catalytic (de)hydrogenation of liquid organic hydrogen carriers, ammonia, and formic acid; and (iii) hydrogen utilization in PEMFCs, AEMFCs, direct liquid fuel cells, and hydrogen-coupled CO₂ and N₂ reduction. Particular emphasis is placed on structure–activity descriptors, operando mechanistic probes, device-level benchmarking from rotating-disk electrodes to membrane-electrode assemblies, and techno-economic considerations including the levelized cost of hydrogen. We conclude by highlighting critical challenges—carbon corrosion, PGM-free durability, and scalable synthesis—and outline future directions that integrate AI-accelerated discovery, atomic-precision synthesis, and biomass-derived circular-economy carbons for next-generation hydrogen technologies. Full article

Lithium-oxygen (Li-O₂) batteries are a compelling next-generation energy storage candidate owing to their ultrahigh theoretical specific energy, but their practical deployment is critically limited by sluggish cathodic oxygen reduction/evolution kinetics, severe polarization, and poor cyclability. Here, we design a composite catalyst consisting of ultrasmall iron clusters uniformly anchored on a three-dimensional nitrogen-doped carbon aerogel (Fe@NC). The material is synthesized via bidirectional freeze-drying followed by high-temperature reduction carbonization using chitosan, cellulose nanocrystals, and zinc acetate; sublimation of zinc during pyrolysis effectively suppresses iron aggregation, yielding highly dispersed Fe0 clusters of ~10 nm while preserving the aerogel’s hierarchical porous architecture rich in pyridinic and pyrrolic N species. Electrochemical tests show that Fe@NC delivers a deep-discharge specific capacity of 18,000 mAh/g, substantially outperforming pristine carbon aerogel and commercial Ketjen black, and maintains stable cycling over 280 cycles at 500 mAh/g. Microscopic and spectroscopic analyses confirm that Fe@NC promotes uniform, fine-particle Li₂O₂ deposition without pore blockage and enables its complete reversible decomposition upon charging, effectively mitigating electrode passivation. This work demonstrates that the synergistic combination of carbon aerogel mass-transport benefits and iron cluster catalytic activity provides a viable, scalable route to high-performance Li-O₂ battery cathodes. Full article

Biowaste-derived porous carbon materials show promise as electrode materials for supercapacitors owing to their low cost, renewable nature, widespread availability, and high specific surface area. Herein, boron and nitrogen co-doped porous carbon was synthesized via a facile one-step activation approach using reed spike as carbon precursor, ammonium borate as both the nitrogen and boron source, and potassium bicarbonate as activator. The prepared PC-700 materials possess large specific surface areas with hierarchical porous architectures and rich N (2.54 at%), O (11.23 at%) and B (2.59 at%) functional groups. As an electrode material, the PC-700 materials show a specific capacitance of 329.6 F g⁻¹ at 0.5 A g⁻¹ and long lifespan. Notably, the assembled PC-700 symmetric super capacitor achieves an energy density of 20.5 Wh kg⁻¹ and excellent electrochemical stabilization (98.60% capacity retention after 10,000 cycles). Full article

Capacitive deionization (CDI) is an environmentally advantageous desalination technology that is particularly suitable for the treatment of low- to medium-concentration saline water. Among different electrode materials, carbon materials are widely used due to their good electrical conductivity and high specific surface area, while they suffer from limited ion adsorption capacity. In this study, a cobalt/nitrogen-doped porous carbon fiber composite with Zn-induced porosity (CoNG@V@CNF), where “V” stands for “volatile pore-forming agent”, has been successfully prepared via electrospinning combined with a high-temperature carbonization process. The introduction of trace Co nanoparticles enhances the stability of porous graphene. In addition, N doping contributes to improved wettability and electronic conductivity, and the carbon fiber structure constructs a three-dimensional conductive network, providing fast channels for ion transport. Electrochemical tests show that the specific capacitance of CoNG@V@CNF reaches 252.76 F g⁻¹, demonstrating its superior charge storage capability. Furthermore, this study achieved a high salt adsorption capacity of 58.28 mg g⁻¹ and a competitive desalination rate performance of 1.94 mg g⁻¹ min⁻¹. After 40 cycles of testing, the salt adsorption capacity (SAC) remains at 56.72 mg g⁻¹, demonstrating its high stability during multiple charging and discharging processes. This work provides a new design strategy for developing high-performance CDI electrode materials. Full article

The development of carbon-based anode materials for high-performance lithium-ion batteries has been limited by their low theoretical capacity density, low conductivity, and high manufacturing costs. Herein, natural Si/N co-doped biomass carbon micron-tubes, derived from reed catkins, were synthesized. The as-prepared RC-Si/N anode exhibits a good discharge capacity of 761.3 mAh g⁻¹ at 100 mA g⁻¹ after 200 cycles. Moreover, it exhibits outstanding cycling stability, retaining discharge capacities of 517.7 mAh g⁻¹ at 1 A g⁻¹ after 1000 cycles. The excellent electrochemical performance is attributed to the trace Si originating from the biomass precursor, which provides high specific capacity, while N doping introduces structural defects and improves electronic conductivity. Coupled with its unique micrometer-scale tubular morphology, the material facilitates efficient lithium-ion transport and storage. Further DFT calculations corroborate enhanced Li⁺ adsorption ability, sustained structural integrity over prolonged cycling, and promoted reaction kinetics. These findings underscore the potential of natural Si/N co-doped biomass-derived carbon as an advanced lithium-ion battery anode material. Full article

Biomass-derived porous carbons are promising supercapacitor electrodes, but their electrochemical performance is often limited by the trade-off between activation-induced pore formation and heteroatom retention. In this work, algae biomass was used as an intrinsic N/O/S-containing precursor to prepare self-nitrogen-doped hierarchical porous carbon by pre-carbonization followed by controlled KOH activation. A temperature-, dosage- and time-dependent sample library was constructed to correlate activation conditions with textural properties, nitrogen configuration, wettability, charge-transfer resistance and electrochemical behavior. The optimized AHPC-850 sample exhibits a BET surface area of 1486 m² g⁻¹, a total pore volume of $0.96$ cm³ g⁻¹, a retained surface nitrogen content of 2.91 at.%, and a charge-transfer resistance of $0.41$$\Omega$. In a three-electrode configuration, AHPC-850 delivers 386 F g⁻¹ at 1 A g⁻¹ and retains 62.4% of its capacitance at 20 A g⁻¹. During 10,000 cycles at 10 A g⁻¹, the electrode maintains 96.3% capacitance retention with a stable coulombic efficiency above 98.8%. A symmetric aqueous device based on AHPC-850 achieves an energy density of $24.8$ Wh kg⁻¹ at 250 W kg⁻¹. These results indicate that algae-derived carbon can be improved by balancing pore accessibility, nitrogen retention and transport resistance rather than by maximizing surface area alone. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

The development of highly efficient, stable, and cost-effective non-precious metal electrocatalysts to replace conventional platinum-based materials holds profound significance for accelerating the commercialization of advanced energy conversion devices, such as zinc–air batteries (ZABs). Herein, we propose a facile and highly efficient strategy to prepare a defect-rich, highly active nitrogen-doped porous carbon-based electrocatalyst (denoted U-Fe-N-C, urea-assisted iron–nitrogen–carbon material), via high-temperature co-pyrolysis of heme with urea. Our results demonstrate that urea not only serves as an excellent nitrogen source during pyrolysis, introducing abundant topological defects and heteroatom doping sites, but also induces the carbon substrate to form a hierarchical sponge-like porous structure with a high specific surface area. This unique microenvironment effectively prevents the agglomeration of iron species at high temperatures, achieving enhanced dispersion of iron species stabilized within the nitrogen-rich carbon matrix. Electrochemical evaluations reveal that under the optimal synthesis conditions (a precursor mass ratio of 1:3, calcination at 900 °C), U-Fe-N-C exhibits excellent oxygen reduction reaction (ORR) catalytic performance, delivering a half-wave potential of 0.731 V vs. RHE, and shows long-term operational durability that significantly surpasses that of commercial Pt/C. Furthermore, liquid rechargeable zinc–air batteries assembled with U-Fe-N-C as the air cathode deliver remarkable cycling stability, operating for up to 270 h of charge–discharge cycling without noticeable performance degradation. This study not only provides useful insights into the mechanisms of pore formation and assistance but also offers a practical perspective for the rational design and scalable synthesis of high-performance metal–nitrogen–carbon (M-N-C) electrocatalysts. Full article

Silica aerogels are ideal candidates for gas adsorption due to their exceptional porosity and high specific surface area; however, the inherent mechanical fragility of their skeletal framework significantly compromises their operational stability in engineering applications. While the incorporation of carbon nanomaterials effectively enhances the mechanical robustness of aerogels, the specific microscopic mechanisms by which filler microstructure and surface chemistry dictate gas adsorption behavior remain insufficiently understood. In this study, we employed all-atom molecular dynamics (MD) simulations to develop a model of silicon-based porous composites synergistically doped with carbon nanotubes (CNTs) and graphene. The adsorption and diffusion characteristics of nitrogen (N₂) were systematically investigated across a CNT doping concentration range of 5% to 20%, and the influence of surface hydrophilicity/hydrophobicity on adsorption performance was quantitatively analyzed by modulating potential energy parameters. Our results demonstrate that the introduction of CNTs reconfigures the porous architecture, leading to an approximately 18.25% increase in the normalized specific surface area, which subsequently drives a 15% enhancement in the overall adsorption capacity of the composite. Nevertheless, analysis reveals that the weight-specific adsorption efficiency of the CNT component itself exhibits a declining trend as the doping concentration increases. This phenomenon is primarily attributed to the convex curvature of the CNTs, which restricts the effective contact area and weakens the adsorption potential, alongside the steric hindrance effects arising from local filler agglomeration at higher concentrations. Furthermore, surface chemical properties exert a significant regulatory influence on adsorption; a strongly hydrophilic modified surface (λ = 1.5) achieved an adsorption capacity approximately 98% higher than the baseline condition—an improvement that exceeds the gains provided by purely physical volume expansion. This research elucidates the synergistic mechanism between physical architecture and surface chemical modification in the adsorption process, suggesting that while the physical architecture determines the abundance of potential adsorption sites, the surface chemistry governs the actual efficiency of site utilization. These findings provide critical theoretical insights for the future design of composite aerogel materials that balance structural stability with superior adsorption performance. Full article

The development of high-performance and sustainable carbon electrodes is increasingly important for next-generation supercapacitors, yet controlling heteroatom doping and hierarchical pore evolution in biomass-derived carbons remains a key challenge. Lignin, as an abundant aromatic biopolymer, offers a structurally rich platform for designing functional carbons, but its rigid cross-linked architecture limits precise pore regulation and efficient nitrogen incorporation. In this work, nitrogen-doped hierarchical porous carbons were engineered from enzymatically treated lignin through a synergistic urea-assisted nitrogen doping and KOH activation strategy. The urea–KOH co-activation drives the coordinated evolution of micropores and mesopores. This approach yields an optimized carbon material possessing a high BET surface area of 2569 m² g⁻¹, an interconnected micro–mesoporous architecture, and a favorable distribution of pyridinic, pyrrolic, and graphitic nitrogen species. The engineered pore hierarchy is correlated with enhanced ion transport kinetics, as evidenced by a high b value of 0.99 and a capacitive contribution of 98.5% at 100 mV s⁻¹; nitrogen functionalities introduce redox-active sites and improve interfacial wettability. As a result, the selected material delivers a high specific capacitance of 221 F g⁻¹ at 0.5 A g⁻¹, strong rate capability with 84.4% retention at 20 A g⁻¹, and excellent cycling durability with 90.7% capacitance retention after 50,000 cycles. This study demonstrates a potentially mechanistically informed, scalable pathway for coupling enzymatic structural regulation with chemical activation, offering a sustainable route for transforming lignin into high-value carbon electrodes suitable for advanced supercapacitor applications. Full article

The large-scale generation of waste graphite not only poses environmental challenges but also provides an opportunity for resource recovery. This study proposes a sustainable strategy that utilizes the graphite cutting waste produced during the production of large graphite electrodes through chemical intercalation, microwave-assisted expansion, and in situ urea nitrogen doping techniques to prepare nitrogen-containing micro-expanded graphite (NMG) composite materials. Structural analysis reveals that the nitrogen-doped amorphous carbon layer formed on the expanded graphite (EG) matrix effectively suppresses excessive expansion while preserving its typical worm-like interlayer morphology and porous structure. XPS confirms successful nitrogen doping with predominant pyridinic-N configuration, introducing abundant defect sites and enhancing lithiophilicity. As an anode for LIBs, NMG delivers an exceptional initial discharge capacity of 1907.5 mAh g⁻¹ at 20 mA g⁻¹ and maintains 798.2 mAh g⁻¹ after 50 cycles, nearly twice that of purified waste graphite (G). Remarkably, after 1000 cycles at 1 A g⁻¹, it retains 650.4 mAh g⁻¹ with 89.9% capacity retention, indicating an electrochemical activation process. Kinetic analysis reveals that the superior performance originates from synergistic diffusion-controlled intercalation and surface-dominated pseudocapacitance, with nitrogen-doped defect sites and hierarchical pore architecture promoting rapid ion/electron transport and surface faradaic reactions. This work demonstrates a viable pathway for value-added upcycling of waste graphite while providing insights into designing high-performance anodes through integrated defect engineering and heteroatom doping. Full article

To enable the efficient and environmentally benign treatment of phenol-containing wastewater, a nitrogen-doped porous carbon material (denoted as 900-CN) was synthesized via high-temperature annealing of a composite composed of humic acid (HA) and g-C₃N₄. The as-prepared materials were characterized, and their catalytic performance in activating peroxymonosulfate (PMS) for phenol degradation was investigated. The results demonstrate that g-C₃N₄ acts as a layered template; upon high-temperature annealing, it gradually evolves into a highly wrinkled and porous architecture. This morphology substantially increases the specific surface area, thereby facilitating pollutant removal. PMS formed metastable surface complexes on 900-CN, enabling concomitant electron transfer. Concurrently, functional groups on the HA-derived carbon reacted with PMS to generate singlet oxygen (¹O₂), a highly oxidative species that markedly enhanced phenol degradation. The 900-CN composite achieved complete phenol removal (100%) within 60 min. Variations in reaction temperature (20–50 °C) and initial pH (2–10) exhibited negligible influence on the performance of the 900-CN/PMS system. Reactive species in the 900-CN/PMS/phenol system included •OH, SO₄^•−, O₂^•−, and ¹O₂, indicating that phenol degradation occurred through combined radical and non-radical pathways. These findings highlight the strong potential of 900-CN as a promising catalyst for the treatment of phenolic wastewater. Full article

Earth-abundant nickel phosphide electrocatalysts show great potential for the hydrogen evolution reaction (HER), yet their efficiency requires further enhancement for practical applications. Herein, a novel in situ strategy is developed to synthesize a high-performance electrocatalyst on nickel foam (NF), composed of N-doped carbon-coated Ni₅P₄–Ni₃P heterostructures. This is achieved through the phosphidation and subsequent carbon coating of hydrothermally grown Ni(OH)₂ nanosheets. The resulting catalyst exhibits excellent HER activity in acidic media, requiring a low overpotential of only 63 mV to achieve a current density of 10 mA cm⁻². The superior performance stems from the synergistic effects of multiple factors: the porous nanosheet architecture and multi-phase interfaces provide abundant active sites, while the conductive N-doped carbon network significantly enhances charge-transfer kinetics and catalyst stability. This work presents an effective approach for designing efficient non-precious metal HER electrocatalysts. Full article