arXiv subjects

Marco Agozzino

Publications and source records attributed to Marco Agozzino.

3 recordsLinked to original sources

arXiv2026

Charge-Transfer Induced Reactivity in sp Carbon Atomic Wires: Towards 0-D sp-sp2 Nanostructures

Carbon Atomic Wires (CAWs) are finite linear chains of sp-hybridized carbon atoms. Here the electrochemical reduction of CAWs in the form of polyynes (i.e. with alternated single-triple bonds) is reported. Upon applying a reducing potential to a solution containing polydispersed hydrogen-capped polyynes, the formation of a black precipitate was observed. Electronic absorption spectroscopy confirmed the irreversible reaction of the carbon chains while excluding degradation or side reactions. Subsequent analyses revealed that the precipitate consisted of amorphous carbon nanoparticles with tunable diameters. This control over particle size is attributed to the modulation of growth kinetics through restricted mass transport toward the solid-liquid interface. Raman spectroscopy showed that the resulting material exhibits an amorphous sp-sp2 character, with a retained sp fraction exceeding 60%. Smaller nanoparticles displayed reduced disorder within the sp2 domains and a broader distribution of sp-chain lengths preserved in the amorphous matrix. Additional experiments on size-selected polyynes suggest that this synthesis method allows to better preserve the starting chain length in the final structure. Unlike previously reported amorphous sp-sp2 carbon networks, the nanoparticles produced in this study show remarkable stability under ambient conditions, retaining their sp character for times in excess of six months. These findings pave the way for future applications, particularly as further diameter tuning may enable access to the quantum-dot regime.

cond-mat.mtrl-sci↗

arXiv2025

Wettability and sp2/sp3 ratio effects on supercapacitor performance of N-doped hydrogenated amorphous Carbon Nanofoam

Pulsed laser-deposited amorphous carbon nanofoams are potential candidate for electrochemical energy storage applications due to ultra-light weight, large volumetric void fractions, and co-existence of sp, sp2 and sp3 carbon hybridization. It is known that charge storage in carbon nanostructures containing disordered sp2-domains is determined by their wettability, surface area, and porosity. However, their charge-storage performance is limited to the areal capacitance of the order of a few mF/cm2. We enhanced the supercapacitor performance of nitrogen-doped amorphous carbon nanofoam by engineering its wettability and sp2-C/sp3-C ratio by vacuum annealing. The specific capacitance was enhanced by about fifty times and the device voltage increased from 0.8 to 1.1 V compared to as-grown carbon nanofoam. In addition, we examined for the first time the initial increase in specific capacitance of the aqueous symmetric supercapacitor with respect to the scan rate, employing in-situ measurements coupling Raman spectroscopy and electrochemistry. We attribute this effect, observed but generally not explained in previous works in the literature, to the electrochemical activation induced by structural changes during the charge storage performance. This optimization of pulsed laser deposited carbon nanofoam may open an avenue for fabricating lightweight and porous nanostructures for advanced macro-to-micro-supercapacitor devices.

cond-mat.mtrl-sci↗

arXiv2025

Low-density functionalized amorphous carbon nanofoam as binder-free Supercapacitor electrode

Nanoporous carbon materials containing small domains of sp2-carbon with highly disordered structures are promising for supercapacitor applications. Herein, we synthesize amorphous carbon nanofoam with 98% volumetric void fraction and low mass density of around 30 mg/cm3 by pulsed laser deposition at room temperature. With the unavoidable oxygen functional groups on the nanoporous surface, carbon nanofoam and nitrogen-functionalized carbon nanofoams are directly grown on the desired substrate under different background gases (Ar, N2, N2-H2), and employed as supercapacitor electrodes. Among the background gases used in synthesis, the use of nitrogen yields nanofoam with higher thickness and more N-content with higher graphitic-N. From the test of amorphous carbon nanofoam supercapacitor device, nitrogenated amorphous carbon electrode shows a higher areal capacitance of 4.1 mF/cm2 at 20 mV/s in aqueous electrolyte, a better capacitance retention at higher current, and excellent cycle stability (98%) over 10000 charge-discharge cycles are achieved compared to not-functionalized counterpart prepared under Ar background gas (2.7 mF/cm2 and cycle stability of 88%).

physics.app-ph↗