Centrum pre nanodiagnostiku materiálov

COSSUTTA, Matteo – VRETENÁR, Viliam – CENTENO, Teresa A. – KOTRUSZ, Peter – MCKECHNIE, Jon – PICKERING, Stephen J.

In Journal of Cleaner Production. Vol. 242, iss. 1 (2020)

https://doi.org/10.1016/j.jclepro.2019.118468

Abstract

Graphene shows substantial promise in improving the technical performance of a range of applications. For its development and before its potential mass adoption, it is critical to understand the associated cradle-to-grave life cycle environmental impacts. Previous studies on graphene environmental performance do not include end of life and the potential environmental credits generated by graphene reuse. This study undertakes a cradle-to-grave approach to evaluating graphene applications, considering a case study of supercapacitors manufactured with graphene and activated carbon active materials. The analysis includes active materials commercial-size production, supercapacitors production, supercapacitors use phase in an automotive application, and their end of life in which both devices are recycled. With current material performance and energy mixes, the graphene-based supercapacitor would increase impacts in all environmental categories analysed, ranging from 27% higher human toxicity to 213% greater ozone depletion and showing a 48% increase in GHG emissions. This unfavourable result arises due to the tested graphene material exhibiting inferior specific capacitance to the activated carbon comparator, as well as a more energy-intensive production process. Prospective analysis considers hypothetical performance where both active materials reach their theoretical specific capacitance, and the decarbonisation of electricity generation. The environmental impacts of both the activated carbon and graphene supercapacitors are reduced in these prospective scenarios, with the graphene based supercapacitor becoming the least impacting solution due to its lower active material requirements. The graphene-based device shows 36% lower GHG emission and overall shows lower impacts ranging from 14% less mineral, fossil and renewable resource depletion to 43% less photochemical ozone formation. These results support graphene as a valid candidate material for substituting activated carbon in supercapacitors provided graphene technical performance is improved, production optimised, and recycling developed.

SOJKOVÁ, Michaela – VÉGSÖ, Karol – MRKYVKOVA, Naďa – HAGARA, Jakub – HUTÁR, Peter – ROSOVÁ, Alica – ČAPLOVIČOVÁ, Mária – LUDACKÁ, Uršula – SKÁKALOVÁ, Viera – MAJKOVÁ, Eva – ŠIFFALOVIČ, Peter – HULMAN, Martin

In RSC Advances. Vol. 9, iss. 51 (2019)

https://doi.org/10.1039/C9RA06770A

Abstract

Few-layer MoS₂ films are promising candidates for applications in numerous areas, such as photovoltaics, photocatalysis, nanotribology, lithium batteries, hydro-desulfurization catalysis and dry lubricants, especially due to their distinctive electronic, optical, and catalytic properties. In general, two alignments of MoS₂ layers are possible – the horizontal and the vertical one, having different physicochemical properties. Layers of both orientations are conventionally fabricated by a sulfurization of pre-deposited Mo films. So far, the Mo thickness was considered as a critical parameter influencing the final orientation of MoS₂ layers with horizontally and vertically aligned MoS₂ grown from thin (1 nm) and thick (3 nm) Mo films, respectively. Here, we present a fabrication protocol enabling the growth of horizontally or vertically aligned few-layer MoS₂ films utilizing the same Mo thickness of 3 nm. We show that the sulfur vapor is another parameter influencing the growth mechanism, where a sulfurization with higher sulfur vapor pressure leads to vertical MoS₂ layers and slow sulfur evaporation results in horizontally aligned layers for a thicker Mo starting layer.

ČAPLOVIČOVÁ, Mária – MAREŠ, Jakub – TOLASZ, Jakub – KOČÍ, Eva – BAKARDJIEVA, Snejana – FAJGAR, Radek – JANDOVÁ, Věra

In Microscopy and Microanalysis. Vol. 25, Suppl. 2 (2019)

https://doi.org/10.1017/S1431927619011875

KUNDRATA, Ivan – FRÖHLICH, Karol – VANČO, Ľubomír – MICUŠÍK, Matej – BACHMANN, Julien

In Beilstein Journal of Nanotechnology. Vol. 10, (2019)

https://doi.org/10.3762/bjnano.10.142

Abstract

Lithiated thin films are necessary for the fabrication of novel solid-state batteries, including the electrodes and solid electrolytes. Physical vapour deposition and chemical vapour deposition can be used to deposit lithiated films. However, the issue of conformality on non-planar substrates with large surface area makes them impractical for nanobatteries the capacity of which scales with surface area. Atomic layer deposition (ALD) avoids these issues and is able to deposit conformal films on 3D substrates. However, ALD is limited in the range of chemical reactions, due to the required volatility of the precursors. Moreover, relatively high temperatures are necessary (above 100 °C), which can be detrimental to electrode layers and substrates, for example to silicon into which the lithium can easily diffuse. In addition, several highly reactive precursors, such as Grignard reagents or n-butyllithium (BuLi) are only usable in solution. In theory, it is possible to use BuLi and water in solution to produce thin films of LiH. This theoretical reaction is self-saturating and, therefore, follows the principles of solution atomic layer deposition (sALD). Therefore, in this work the sALD technique and principles have been employed to experimentally prove the possibility of LiH deposition. The formation of homogeneous air-sensitive thin films, characterized by using ellipsometry, grazing incidence X-ray diffraction (GIXRD), in situ quartz crystal microbalance, and scanning electron microscopy, was observed. Lithium hydride diffraction peaks have been observed in as-deposited films by GIXRD. X-ray photoelectron spectroscopy and Auger spectroscopy analysis show the chemical identity of the decomposing air-sensitive films. Despite the air sensitivity of BuLi and LiH, making many standard measurements difficult, this work establishes the use of sALD to deposit LiH, a material inaccessible to conventional ALD, from precursors and at temperatures not suitable for conventional ALD.