Abstract
Lignin nano-particles (LNPs) exhibit properties that distinguish them with regard to production of lignin-based materials. However, little research has been performed to investigate whether porous carbons produced from LNPs exhibit performance superior to those derived from untreated lignin. In this study, lignin was fabricated into lignin nano-particles (LNP) and used to prepare high-performance porous carbons with enhanced thermal conductivities comparing to that of the carbons from neat lignin. Two different preparation protocols were employed: direct pyrolysis and hydrothermal carbonization followed by pyrolysis. Carbons obtained from 100 nm–300 nm LNPs possessed more graphene-like structures than carbons from unaltered lignin. In addition, carbons prepared using a combination of hydrothermal carbonization and pyrolysis exhibited higher specific surface areas (108.81 m2/g–220.75 m2/g) and total pore volumes (0.098 cm3/g–0.166 cm3/g) than those prepared via direct pyrolysis. In addition, LNP-derived carbons exhibited superior thermal conductivities (0.45 W/mK) and thermal conductivity rates (0.51 oC/s). This work provides the useful finding that superior graphene-like porous carbons can be produced by transforming lignin into LNP and then hydrothermally carbonizing the resulting material prior to pyrolysis.
Highlights
Graphene is a type of two-dimensional material composed of sp2-structured monolayer carbon
A solvent-free, high-pressure homogeneous technology was used to fabricate Lignin nano-particles (LNPs) from kraft lignin. The purpose of this effort was to explore whether LNP could be pyrolyzed into graphene-like porous carbons with better properties than those made from untreated lignin
According to the aforementioned results, it can be seen that the LNP-based carbons produced via protocol 2 contain more desirable features, such as smooth surfaces with creases and multi-layers with thin lamels (Figure 2f), than those produced via protocol 1. These results indicate that the combination of hydrothermal carbonization and pyrolysis generates porous carbons with greater morphological similarity to graphene-like structures than pyrolysis alone
Summary
Graphene is a type of two-dimensional material composed of sp2-structured monolayer carbon. High-quality graphene can be obtained via the aforementioned methods, urgent technical and biological issues remain These issues include a lack of mass production capacity, as well as environmental and human health concerns due to a reliance on toxic or hazardous reagents (Vlassiouk et al, 2013). To avoid these issues while maintaining the desired graphene properties, researchers have developed several graphene-like materials such as carbon nitride sheets, activated porous carbon (Ojha et al, 2017), carbon nanotubes (Araujo et al, 2012), and MoS2 nanoplates (Hwang et al, 2011). These materials offer performances that are comparable to that of graphene for various applications
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