Synthesis and properties of free-standing monolayer amorphous carbon

Abstract

Bulk amorphous materials have been studied extensively and are used widely. Yet, their atomic arrangement remains an open issue. They are generally believed to be Zachariasen continuous random networks (Z-CRNs) 1 , but recent experimental evidence favours the competing crystallite model in the case of amorphous silicon 2-4 .Corresponding questions in 2D materials are wide open. Here we report the synthesis of centimetre-scale, freestanding, continuous, and stable monolayer amorphous carbon (MAC), topologically distinct from disordered graphene, by laser-assisted chemical vapour deposition 5 . Unlike bulk materials, the amorphous structure of MAC can be determined by atomic-resolution imaging. Extensive characterisation reveals complete absence of long-range periodicity and a threefold-coordinated structure with a wide distribution of bond lengths, bond angles, and 5-, 6-, 7-, and 8-member rings. The ring distribution is not a Z-CRN but resembles the competing (nano)crystallite model 6 . A corresponding model has been constructed and enables density-functional-theory calculations of MAC properties, in accord with observations. Direct measurements

Reactive Plasma N-Doping of Amorphous Carbon Electrodes: Decoupling Disorder and Chemical Effects on Capacitive and Electrocatalytic Performance

“…60% after 5 min exposure, while leveling off at approximately twice the value of the nitrogen-free material after 10 min. This is consistent with the introduction of both N-sites and defects; these are known to result in (i) an increased density of mid-gap localized/surface states (Van Tuan et al, 2012;Zhong et al, 2014;Velický et al, 2019;Toh et al, 2020) which lead to increased interfacial capacitance (Wiggins-Camacho and Stevenson, 2009;Tian et al, 2015;Velický et al, 2019), albeit at the expense of delocalization; and (ii) an increase in electrode roughness and consequently its electrochemical specific surface area (ECSA). A similar increase of the capacitance by a factor of 2 is observed at 10 Hz; notably, a comparison of values obtained at 0.1 vs. 10 Hz indicates dispersion in the capacitive response.…”

WITHDRAWN: Amorphizing noble metal for single-atom-layer catalysis

“…Different from previously reported carbon amorphous monolayers 13 (0.6 nm thickness), our amorphous PtSe x layer is made of Pt and Se atoms with more complicated coordination and, to the best of our knowledge, is the rst binary amorphous layer. Notably, our amorphous layer can be thermodynamically stable in a 2D form with a thickness down to 1 nm.…”

Structural relaxation probed by resistance drift in amorphous germanium

“…Their arguments are in line with the views of Cheng. In 2020, Özyilmaz group prepared free-standing monolayer amorphous carbon, and it was found that it was reasonable to describe its structure by MRO model rather than CRN model [23].…”