The pursuit of high-performance hard carbon anodes is hindered by the difficulty of simultaneously regulating local graphitization degree and closed-pore structure through conventional, lengthy chemical activation. Herein, we propose a dilute oxygen-water vapor flash etching strategy to rapidly convert waste pyrolytic carbon black (CBp) into a sustainable hard carbon anode. In situ experiments, DFT calculations, and machine learning simulations reveal that the introduced water molecules create a new proton-transfer catalyzed flash etching (PTCFE) process, where H+ and OH⁻ are proposed to act as “molecular scissors” in a DFT-supported proton-transfer pathway to open up multiple parallel low-barrier pathways, reducing the activation energy barrier and accelerating the etching from several hours to just 40 s. This transient treatment triggers the rapid formation of a metastable carbon architecture featuring short-range ordered graphitic microdomains and closed turbostratic-like nanopores, enabling exceptional plateau sodium storage. The high-throughput screened CBp-40s achieve a significantly prolonged discharge capacity of 392.5 mAh g−1 at 20 mA g−1 with a long low-voltage plateau capacity of 173.1 mAh g−1, achieving a nearly 690% increase over pristine CBp, along with exceptional durability at 10 A g−1, outperforming the state-of-the-art literature. Techno-economic analysis further validates the feasibility of converting bulk spent carbon into sustainable HC anodes for high-performance sodium-ion batteries.

The electrode-electrolyte interface engineering is paramount to advancing bifunctional porous carbon materials for zinc-hybrid supercapacitors (ZHSCs) and sodium-ion batteries (SIBs). Herein, a coordination-pyrolysis method is proposed to synthesize Ag-nanoparticle-decorated bimetallic MOF-derived carbon nanorods (Ag-BMNR-2), wherein the interfacial architecture is synergistically engineered through three mechanisms: (i) evenly dispersed Ag nanoparticles introduce electron-rich colloidal sites that reduce charge-transfer resistance and accelerate interfacial electron transport via a continuous Ag → Ag → Ag conductive network; (ii) chemical activation generates oxygen-rich surface functionalities (CO, CO, OH) that enhance electrolyte wettability and provide dipole-ion coupling sites for Na+ coordination; and (iii) a hierarchical micro-mesoporous architecture maximizes ion-accessible interfacial area. Theoretical calculations and in/ex situ characterization confirm that Ag doping lowers the Na+ diffusion barrier, strengthens adsorption affinity, and elevates the electronic density of states near the Fermi level. Benefiting from this synergistically engineered interface, Ag-BMNR-2 delivers 364.7 F g-1 at 1 A g-1, retaining 95.6% capacity after 100,000 cycles in SCs, and achieves 458.6 mAh g-1 at 0.05 A g-1 with 90.1% capacity retention over 700 cycles in SIBs (ICE: 69.9%). This work establishes interface engineering of Ag-decorated hierarchical porous carbon as a versatile strategy for dual-functional energy storage materials.

One of the main concerns of mankind nowadays is the proper generation and storage of energy as this matter became the support for the proper functioning of any other technology. Alongside that, the implications for finding alternative energy sources increase the pressure for the development of novel materials that can simultaneously generate or store energy sustainably and efficiently. For that, understanding the main technologies present in society along with the core materials that can serve as components is a highly regarded knowledge. Based on these aspects, this book chapter focuses on providing a diverse yet precise discussion regarding the main technologies related to energy such as supercapacitors, batteries, photovoltaic cells, fuel cells, electrolyzers, and piezo and thermoelectric devices. Also, to further address this topic the final session of the chapter is devoted to the most research electroactive materials that are employed in these technologies. This discussion is backed by the most recent literature work to provide the main concepts as well as encourage the readers to obtain novel ideas related to the vast field of materials suitable for energy applications such as carbon-based nanomaterials, MXenes, transition metal oxides, sulfides, phosphides, Si-based nanomaterials, and its respective composites.

The rational modulation of interfacial electronic structure is critical for optimizing oxygen reduction reaction (ORR) activity of Fe-N4-based electrocatalysts. Herein, density functional theory (DFT) calculations were employed to systematically investigate the ORR activity of pristine FePc, FePc@graphene, axially coordinated FePc via N-atom of pyridine (FePc-Py-G), phenylpyridine (FePc-Py-Ph-G) and biphenylpyridine (FePc-Py-Ph-Ph-G), which are covalently linked with graphene. The results reveal that covalent graphene integration and axial FeN coordination synergistically regulate the Fe 3d electronic states, significantly altering the adsorption energetics of ORR intermediates. Among all systems, FePc-Py-Ph-G catalyst exhibits the optimal ORR activity with a limiting potential of 0.86 V and a low overpotential of 0.37 V, outperforming other constructed models. The enhanced ORR activity of FePc-Py-Ph-G originates from balanced adsorption free energies of *OOH (3.89 eV), *O (1.67 eV), and *OH (0.79 eV), facilitated by efficient interfacial charge redistribution and strong FeN orbital hybridization. In contrast, excessive conjugation in FePc-Py-Ph-Ph-G system weakens electronic coupling, resulting in relatively inferior ORR activity. This work establishes conjugation-length-dependent interfacial electronic modulation in FePc-based hybrid electrocatalysts to approach their superior ORR activity.

ABSTRACT The rising atmospheric CO2 concentration has intensified interest in technologies that couple carbon utilization with the production of high‐value functional materials. Direct conversion of captured CO2 into carbon architectures offers a distinct route in which emissions are transformed into electrochemically active solids rather than molecular fuels or commodity chemicals. Unlike conventional carbons, CO2‐derived carbons are generated through thermochemical, electrochemical, plasma‐assisted, and hybrid conversion pathways that reconstruct carbon frameworks from fully oxidized molecular feedstocks. These synthesis routes enable hierarchical porosity, tunable graphitic order, high defect densities, and heteroatom‐coordinated active sites, providing opportunities to engineer electronic structure and interfacial reactivity across multiple length scales. This review examines how synthesis conditions govern structural evolution and how these features dictate performance in electrocatalytic and electrochemical energy‐storage systems. Emphasis is placed on defect‐mediated active sites, heteroatom coordination, interfacial charge redistribution, and metal–carbon interactions that control oxygen reduction, oxygen evolution, and hydrogen evolution reactions. The roles of CO2‐derived carbons in lithium‐ion, sodium‐ion, lithium–sulfur, and related battery chemistries, as well as electrochemical capacitors, are evaluated through their influence on ion transport, charge‐transfer kinetics, and storage mechanisms. Recent advances reveal that CO2 conversion can encode functionality directly during synthesis, eliminating many post‐synthetic modification steps. However, significant barriers remain, including scalable manufacturing, deterministic defect control, long‐term stability, and rigorous environmental and economic assessment. Future progress will depend on integrating operando characterization, theory‐guided design, machine learning, and life‐cycle analysis to establish predictive design rules and accelerate deployment in sustainable energy technologies.

Over the past decade, there has been a significant increase in the concentration levels of arsenic and fluoride in surface water, which cause severe diseases such as fluorosis and arsenicosis. In this study, a hydrogel of arsenicosis oxide with basic zirconium hydroxide (BZrH@GHG) was efficiently synthesized and effectively used for the removal of fluoride (F-) and arsenic (As(III)). Hydrogels, 3D porous structures, have been developed as super adsorbents to adsorb fluoride ions from the water. The network structure of the hydrogel can adsorb large amounts of water, and the buried water enhances the adsorption capacity of the adsorbent. The BZrH@GHG has a high surface area of 821.816 m(2)/g, which handles its excellent monolayer adsorption capacity of F- and As(III), i.e., 250 and 125 mg/g, respectively. The kinetics of the removal of F- and As(III) follow the pseudo-second-order model with a high rate constant of 95.23 and 94.10 g mg(-1)min(-1), respectively. The thermodynamics study reveals that adsorption is workable, spontaneous, and endothermic. The point of zero charge for BZrH@GHG was found to be 7.3. It was suitable for adsorbing F- and As(III); arsenic exists as H3AsO3 in the pH range of 3 -8. At pH 9, some H3AsO3 is converted to H2AsO3- and can easily be adsorbed on the BZrH@GHG. The XPS study explains that hydroxyl groups participate in the adsorption of fluoride and arsenic by ion-exchange and complexation mechanisms, respectively.

Zinc oxide nanoparticles (ZnO NPs) have already shown potential applications as antimicrobial agents. However, the large band gap and charge carrier recombination of ZnO NPs reduce the production of reactive oxygen species, which limits their antibacterial activity; therefore, further modifications of their structural and electronic properties are required. Herein, Cu doping of ZnO NPs has been carried out by a microwave-assisted method to modify their structural, electronic, and biological properties. The structural and morphological analysis of the prepared Cu-doped ZnO NPs confirmed that Cu is well incorporated into the ZnO NPs lattice, and the morphology is quasi-spherical with a diameter range of 20–25 nm. The changes in the band gap and defect states in ZnO NPs, formed upon Cu doping, were confirmed by UV-visible and theoretical analysis. The antimicrobial potential of ZnO and Cu-doped ZnO NPs against S. aureus, E. coli, P. aeruginosa, and C. albicans has been evaluated by measuring the zone of inhibition, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The results showed an enhancement of the antimicrobial potential of ZnO NPs upon Cu doping, which could be related to modifications of the electronic structure that could potentially affect redox properties.

Given the ubiquity of electrical devices in the modern day, energy production is of paramount concern. Smartphones, the internet, and climate control systems are almost required for modern living, and all require energy to operate. Subsequently, efficient energy generation is needed as the global population increases. While many renewable energy options are available, hydrogen fuel cells demonstrate the most efficiency. The use of these fuel cells begets the need for clean hydrogen. Methane reforming exists as the most widely used method for hydrogen generation. However, this process also produces greenhouse gas emissions. As such, water electrolysis stands as an attractive option for hydrogen synthesis. In order to split hydrogen and oxygen from water, good electrocatalysts are needed. While there are many options available, transition metal phosphides have demonstrated excellent properties for this application. Low cost, wide availability, and excellent tunability are all hallmarks of transition metal phosphide applications for water electrocatalysis. As such, the synthesis, structures, and electrocatalytic activity of different metal phosphides must be explored if a clean energy future is desired.

Dual-atomic sites offer superior oxygen reduction reaction (ORR) activity through cooperative O2 activation, yet their construction via conventional routes lacks atomic precision and structural clarity. Face-to-face stacking of molecular MN4 units provides a rational alternative to construct well-defined dual sites, though precise intersite distance control for stabilizing trans-bridged M1-O-O-M2 species remains challenging and can be effectively guided by density functional theory. Herein, we theoretically constructed a pair of well-defined adjacent Fe-Co dual active sites by face-to-face coupling of FeN4 and CoN4 single-atomic units. Systematic optimization of the interlayer distance reveals that a separation of 4.0 & Aring; is optimal for O2insertion and stabilizes a trans-bridged Fe-O-O-Co configuration, which is crucial for facilitating the 4e-ORR pathway. Electronic structure analysis demonstrated strong charge redistribution and enhanced metal-oxygen coupling in the dual-site architecture compared with single-atomic counterparts. Further, the free-energy calculations showed spontaneous O2 adsorption and dissociation over adjacent Fe-Co dual active sites at U = 1.23 V, yielding a remarkably low ORR overpotential of 0.21 V, substantially lower than that of isolated FeN4 (0.84 V) and CoN4 sites (0.88 V). The lowered barrier was a result of the cooperative regulation of OH* by neighbouring Fe-Co sites. This study offers basic insights into dual-atomic site engineering based on single-site molecular models and serves as a theoretical guideline for the design of next-generation ORR electrocatalysts.

Developing multifunctional nanomaterials with improved antibacterial properties and reliable biocompatibility is an essential issue in biomedical research to address the increasing concern of antibiotic resistance. Ag-doped zinc oxide nanoparticles (ZnO NPs) were synthesized using a green and eco-friendly route using hibiscus flower extract as a reducing and stabilizing agent. The nanoparticles were synthesized successfully and characterized through FT-IR, TEM, EDX, and UV-Vis analysis. The bactericidal action potential was tested against E. coli, S. aureus, B. subtilis, Lactobacillus, and C. albicans pathogens using the Kirby-Bauer disk diffusion method. Ag-doped ZnO NPs were observed to have superior inhibition action against E. coli compared to pristine ZnO NPs. The interactions of ZnO and Ag-ZnO NPs towards calf thymus DNA (ct-DNA) were examined spectroscopically using absorption and fluorescence studies. It was observed that Ag-doped ZnO NPs showed a greater interaction with ct-DNA than pristine ZnO NPs. Thus, we conclude that biosynthesized Ag-ZnO NPs are multifunctional nanomaterials with good antibacterial action, an improved ability to bind to DNA, and better biocompatibility for future biomedical applications.

The oxygen reduction reaction (ORR) remains a critical kinetic bottleneck in fuel cells and metal–air batteries, necessitating the development of highly active and durable non-precious-metal electrocatalysts. Among emerging candidates, Fe–N–C materials have attracted significant attention owing to their high intrinsic activity, tunable electronic structure, and low cost. Recent studies have demonstrated that boron incorporation provides an effective strategy for overcoming the limitations of conventional Fe–N–C catalysts through atomic-scale interface engineering. Boron-induced electronic modulation alters the charge distribution, spin state, and coordination environment of Fe–Nx active centers, thereby optimizing oxygen adsorption energetics and accelerating ORR kinetics. This review summarizes recent advances in boron-modulated Fe–N–C electrocatalysts, focusing on synthesis strategies, electronic structure regulation, interfacial charge transfer, orbital hybridization, and oxygen reduction mechanisms. Particular emphasis is placed on the role of boron in engineering Fe–N/B–C interfaces, promoting active-site utilization, improving catalytic selectivity, and enhancing durability. Finally, current challenges associated with active-site identification, catalyst stability, operando characterization, and scalable synthesis are highlighted, together with future opportunities for the rational design of next-generation Fe–N–C electrocatalysts for sustainable electrochemical energy-conversion technologies.

Hard carbon (HC) is recognized as a promising anodic material for sodium-ion batteries (SIBs). However, insufficient reversible capacity, low initial coulombic efficiency (ICE), and unsatisfactory specific capacity limit its practical application. Herein, a "Dilute-O2-Flash-Etching" (DOFE) strategy is proposed to generate numerous closed pores in spent coconut shell-derived HC in seconds with significantly increased reversible storage capacity at the low-voltage plateau. Theoretical calculations, in/ex situ tests reveal that new open pores are firstly formed on the carbon substrate during the DOFE process and subsequently reorganized into closed pores by in situ carbonization, resulting in a new "open-pore to closed-pore" transformation and a related Na ion filling storage mechanism. The new HC exhibits an excellent reversible capacity of 411.2 mAh g- 1 and a superior ICE of up to 90.6%, while achieving a remarkable increase in plateau capacity from 175 to 279.2 mAh g-1, which far exceeds the reported capacities of biomass-derived HCs. Moreover, the full cell offers a high energy density of 269.7 Wh kg- 1 and superior stability. These findings provide a novel paradigm for the cost-effective fabrication of highperformance HC anodes.

The oxygen reduction reaction (ORR) is a cornerstone of sustainable energy conversion technologies, such as fuel cells, metal–air batteries, and green synthesis of H2O2. However, the widespread adoption of ORR is hindered by persistent challenges in terms of catalytic activity, selectivity, and durability of the catalysts. A transformative approach to overcome these limitations is the chemical engineering of metal‑nitrogen‑carbon single-atom catalysts (M-N-C SACs), which allows precise tuning of electronic structures and coordination environments to mimic the efficiency of natural metalloenzymes. The electronic structure of M-N-C SACs can be modulated by incorporation of heteroatoms (e.g., S, B), which alter the d-band structure to enhance O2 adsorption and OO bond cleavage, consequently reducing the overpotential for ORR. Atomic-scale engineering of bond lengths, coordination numbers, and electronic states in metal‑nitrogen‑carbon single-atom catalysts (M-N-C SACs) significantly improves their ORR performance. Specifically, the engineering of the first and higher coordination spheres through ligand design or hetero-element doping enhances charge transfer dynamics and selectivity of 4e- process, which is a key step in ORR. This review systematically evaluates the influence of coordination engineering in M-N-C SACs on benchmark ORR metrics, while highlighting breakthroughs in operando techniques and advanced electron microscopy that resolve active-site dynamics under working conditions. This study highlights the integration of density functional theory (DFT) predictions with experimental validation to demonstrate the synergy between tailored coordination environments and catalytic activity. Finally, the existing challenges, such as the scalability of defect-engineered SACs and their long-term stability in acidic media, are discussed in the context of emerging catalytic materials. In addition, the opportunities in machine learning-guided design and plasma-enhanced synthesis of hierarchical N-doped carbons for electrode engineering are discussed.

Pristine MoS2 exhibits sluggish kinetics for both oxygen and hydrogen evolution reactions (OER and HER) due to its restricted active sites and inadequate conductivity; however, strategic doping can impose significant improvement of catalytic performance by altering the electronic structure and revealing additional active edge sites. The Sn-doped MoS2 nanomaterial was grown on Ni-foam (Sn-doped MoS2@Ni-foam) using the microwave-assisted hydrothermal method, followed by characterization by several analytical techniques. The electrochemical investigations revealed that Sn-doped MoS2@Ni-foam exhibited exceptional OER and HER performance, with minimal overpotentials of 259 and 149 mV at a current density of 10 mA/cm2, in contrast to pristine MoS2@Ni-foam, demonstrating overpotentials of 307 and 254 mV at the same current density. Theoretical investigations indicated that Sn-doping successfully altered the electronic structure and optimised the active sites of MoS2, enhancing overall catalytic efficiency. This study offers an innovative approach for the synthesis of highly efficient, economical electrocatalysts for water splitting, with potential applications in clean energy generation along with sustainable hydrogen production.

The oxygen reduction reaction (ORR) remains a critical bottleneck in the advancement of electrochemical energy conversion technologies, necessitating the development of efficient and durable alternatives to noble metal catalysts. Iron phthalocyanine (FePc), featuring well-defined Fe-N4 active centres, has emerged as a promising molecular catalyst; however, its practical application is hindered by limited conductivity, aggregation, and stability issues. This review provides a comprehensive overview of recent progress in engineering FePc-based hybrid catalysts through integration with carbon nanostructures, particularly graphene and carbon nanotubes (CNTs), with an emphasis on heteroatom doping strategies. We discuss fundamental ORR mechanisms, key performance metrics, and design principles governing FePc/carbon composites. Special attention is given to interface engineering, where electronic coupling, charge redistribution, and structural stabilization play decisive roles in enhancing catalytic activity. Benchmarking strategies are systematically analyzed by comparing pristine and heteroatom-doped (N, B, S, and P) graphene/CNT-FePc systems, highlighting the influence of dopant type and interfacial interactions on ORR pathways and kinetics. Finally, current challenges, including stability in acidic media and scalability, are addressed alongside future perspectives such as multi-doping, single-atom catalysts, and device integration. This review aims to guide the rational design of next-generation FePc-based ORR electrocatalysts.

A new chiral cadmium(II) coordination polymer, poly[[[1,10-phenanthroline-kappa 2N,N ']cadmium(II)]-mu 3-tartrato kappa 2O,O ':kappa O ':kappa O ''] ([Cd(ta)(phen)]n), was synthesized using 1,10-phenanthroline and tartaric acid as ligands. The compound was prepared under mild solution conditions and characterized by single-crystal X-ray diffraction, FTIR, Raman, UV-Vis spectroscopy, thermal analysis, SEM-EDS, BET, Powder X-ray diffraction (PXRD), and Hirshfeld surface analysis. Single-crystal XRD confirmed a two-dimensional layered structure with a distorted seven-coordinate Cd(II) centre, stabilized by both classical and non-classical hydrogen bonds as well as it-it stacking interactions. PXRD analysis confirmed that the bulk sample retains phase purity consistent with the single-crystal structure. Elemental mapping via SEM-EDS demonstrated uniform distribution of Cd, N, C, and O atoms. Hirshfeld surface and fingerprint plots revealed dominant H & sdot;& sdot;& sdot;O and H & sdot;& sdot;& sdot;H interactions, highlighting the role of non-covalent forces in crystal packing. Importantly, antimicrobial studies revealed strong inhibitory effects of [Cd(ta)(phen)]n against Candida albicans, Escherichia coli, and Bacillus subtilis, outperforming individual precursors and suggesting synergistic effects. The results underscore the potential of this compound as a multifunctional material with promising applications in antimicrobial and bioinorganic chemistry.

The construction and packaging industries are heavily dependent on petroleum-derived products such as polyurethane (PU) and polystyrene foams, as well as energy-intensive mineral and rock wool. Their low thermal conductivity, moisture resistance, long-term durability, low cost, and wide availability have made these materials difficult to substitute. However, in recent years, there has been growing demand for sustainable, renewable, and environmentally friendly alternatives to petroleum-derived products, driving considerable research and development in this area. Several natural materials, including wood fiber, hemp fiber, and rice and wheat straw fibrous panels, have been utilized for thermal insulation applications in the construction sector. These materials offer notable advantages such as low thermal conductivity, high porosity, and tuneable mechanical properties, alongside inherent biodegradability and a reduced carbon footprint. Nevertheless, significant challenges remain, particularly with respect to moisture resistance, thermal stability, and continued reliance on fossil-derived binders in their production. In the present work, binderless foams based on common reed (Phragmites australis) were produced using hydrothermally treated and reactive extrusion-processed reed fibers. The resulting foams demonstrated thermal conductivity comparable to that of PU and polystyrene foams, along with adjustable density. Moreover, the reed foams exhibited excellent dimensional stability under both water immersion and high humidity conditions. This work also provides a comprehensive characterization of the chemical composition of common reed before and after various treatments, as well as the process know-how required for binderless foam production.

The oxygen reduction reaction (ORR) remains the kinetic bottleneck in fuel cells and metal-air batteries, demanding highly active and durable electrocatalysts beyond precious-group metals. In this regard, Fe/Co dualatomic electrocatalysts (DACs) have emerged as a promising class of materials in which atomically dispersed Fe and Co sites, positioned in close proximity, enable tunable electronic coupling and optimized oxygen intermediates binding. This review critically examines the distinct and cooperative roles of Fe and Co centers in Fe/ Co DACs, correlating structural motifs, coordination environments, and electronic communication with ORR performance. It discusses the classification and engineering approaches for Fe/Co DACs along with their advanced characterization, elucidating the Fe-Co synergy at the atomic scale. Particular emphasis is placed on doping, defect regulation, and coordination engineering in light of density functional theory (DFT) insights to benchmark intrinsic activity and selectivity. By systematically analyzing structure-property-performance relationships, this review identifies key descriptors governing catalytic efficiency and durability. Finally, we outline current challenges and future directions toward rational design of DACs, providing a comprehensive framework for advancing high-performance, non-precious ORR electrocatalysts.