Heteroatom Codoped Graphene: The Importance of Nitrogen

Theoretical Characterization of Germanene Doped with Main Group Elements

Herein, using density functional calculations, we studied the substitutional doping in germanene with B, C, N, O, Al, Si, P, S, Ga, As, and Se. Nitrogen is the element that can be more easily incorporated into the germanene lattice, followed by silicon, carbon, and boron. Almost all dopants were efficient in opening a band-gap. Yet, caution should be taken because this opening strongly depends on the dopant concentration. Carbon and sulfur were the most effective elements for band-gap opening. C-doping generates the lowest effective masses (me*/m0=mh*/m0=0.09). The equal me and mh values indicate an intrinsic semiconductor behavior, a characteristic shared by the chalcogenides-doped systems. Additionally, we performed a detailed analysis of the preferred disposition of dopants in the germanene lattice. In contrast with the results obtained for graphene, when multiple atoms are introduced in the germanene framework, they do not prefer to be agglomerated, adopting a random disposition, except in the case of sulfur and nitrogen, which favored specific dopant arrangement. Two sulfur dopants showed a notorious preference for replacing a Ge-Ge bond but without forming an S-S linkage, thus adopting a thiophene-like structure that may impart germanene exciting properties, as observed for S and N codoped graphene.

Structural and electronic properties of Li-adsorbed single and bilayer porphyrin sheets as an electrode material for energy storage devices - a DFT analysis

In this study, we adopt density functional theory (DFT) to investigate the structural and electronic properties of monolayer and bilayer 2-D porphyrin sheets (PS) of covalent organic frameworks (COFs) upon interaction with Li atoms as an electrode material for Li-ion batteries. Based on their mechanical properties, our systems exhibit remarkable stability. The adsorption of Li at various sites in the monolayer, including over and between the bilayers of PS, is investigated. Our results indicate that Li at site S3 has the highest adsorption energy, and Li is energetically preferred to intercalate within the bilayer rather than monolayers due to its high adsorption energies. Notably, the charge transfer remains consistent for both systems. The density of state distribution, charge density difference plots, spin density and the band structure results show that the PS has high electrical conductivity. Additionally, the reaction potential was carried out, and the negative reaction potential results demonstrate that the system undergoes a reduction reaction. The resultant theoretical capacity and the open circuit voltage highlight that the PS materials of COFs are an important step for use in the next generation high-performance lithium-ion batteries.

Enhanced efficiency of photocatalytically synthesised Co3+/Co2+-incorporated CeO2/SnO2 nanocomposite and supercapacitor studies

The photochemical reduction approach, distilled H2O with PriOH as the solvent medium, was used to create and characterise the conversion of Co3+ to Co2+ integrated on CeO2/SnO2. The PXRD, IR, SEM, HR-TEM, VSM, and XPS results show that the materials generated have appropriate crystallisation form and retain the hollow spherical structure of Co-CeO2/SnO2. The performance of several UV-light energetic photocatalysts and the reaction pathways for inorganic complex degradation are addressed, emphasising the main elements contributing to their mineralisation. Reaction mechanisms, identification and quantification of degradation intermediates, and effects of reactive active species were described and analysed for each modelled target inorganic pollutant category. The ternary (Co3+/Co2+)/CeO2/SnO2 materials were hypothesised to improve the photocatalytic activity by increasing the transport rate of eCB- impurities as a result of accelerating the practical separation of electron-hole (e-/h+) pairs. Then, it exhibits high cycling stability by successfully reducing the pulverisation of Co-CeO2/SnO2 electrode materials due to volume expansion and a high specific capacity of 827 F g-1(1 A g-1) while maintaining a high current density of 5 A g-1. GCD and impedance spectroscopy studies were also carried out to analyse charge-discharge cycles and sample stability. This exceptional electrochemical performance suggests that Co-CeO2/SnO2 are promising for high-performance energy storage systems.

Stannate-Based Materials as Anodes in Lithium-Ion and Sodium-Ion Batteries: A Review

Binary metal oxide stannate (M₂SnO₄; M = Zn, Mn, Co, etc.) structures, with their high theoretical capacity, superior lithium storage mechanism and suitable operating voltage, as well as their dual suitability for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), are strong candidates for next-generation anode materials. However, the capacity deterioration caused by the severe volume expansion problem during the insertion/extraction of lithium or sodium ions during cycling of M₂SnO₄-based anode materials is difficult to avoid, which greatly affects their practical applications. Strategies often employed by researchers to address this problem include nanosizing the material size, designing suitable structures, doping with carbon materials and heteroatoms, metal-organic framework (MOF) derivation and constructing heterostructures. In this paper, the advantages and issues of M₂SnO₄-based materials are analyzed, and the strategies to solve the issues are discussed in order to promote the theoretical work and practical application of M₂SnO₄-based anode materials.