{"id":142367,"date":"2024-04-18T07:23:00","date_gmt":"2024-04-18T05:23:00","guid":{"rendered":"https:\/\/renewable-carbon.eu\/news\/?p=142367"},"modified":"2024-04-16T11:49:40","modified_gmt":"2024-04-16T09:49:40","slug":"fungal-carbon-a-cost-effective-tunable-network-template-for-creating-supercapacitors","status":"publish","type":"post","link":"https:\/\/renewable-carbon.eu\/news\/fungal-carbon-a-cost-effective-tunable-network-template-for-creating-supercapacitors\/","title":{"rendered":"Fungal Carbon: A Cost-Effective Tunable Network Template for Creating Supercapacitors"},"content":{"rendered":"\n\n\n

Abstract<\/h3>\n\n\n\n

Carbons form critical components in biogas purification and energy storage systems and are used to modify polymer matrices. The environmental impact of producing carbons has driven research interest in biomass-derived carbons, although these have yield, processing, and resource competition limitations. Naturally formed fungal filaments are investigated, which are abundantly available as food- and biotechnology-industry by-products and wastes as cost-effective and sustainable templates for carbon networks. <\/p>\n\n\n

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\"\"<\/figure><\/div>\n\n\n

Pyrolyzed\u00a0Agaricus bisporus<\/em>\u00a0and\u00a0Pleurotus eryngii<\/em>\u00a0filament networks are mesoporous and microscale with a size regime close to carbon fibers. Their BET surface areas of \u2248282 m2<\/sup>\u00a0g\u22121<\/sup>\u00a0and \u224860 m2<\/sup>\u00a0g\u22121<\/sup>, respectively, greatly exceed values associated with carbon fibers and non-activated pyrolyzed bacterial cellulose and approximately on par with values for carbon black and CNTs in addition to pyrolyzed pinewood, rice husk, corn stover or olive mill waste. They also exhibit greater specific capacitance than both non-activated and activated pyrolyzed bacterial cellulose in addition to YP-50F (coconut shell based) commercial carbons. The high surface area and specific capacitance of fungal carbon coupled with the potential to tune these properties through species- and growth-environment-associated differences in network and filament morphology and inclusion of inorganic material through biomineralization makes them potentially useful in creating supercapacitors.<\/p>\n\n\n\n

1 Introduction<\/h3>\n\n\n\n

Carbons are widely used in materials science as absorbents, e.g., for biogas purification (H2<\/sub>S removal),[<\/sup>1<\/a><\/sup>]<\/sup> fillers for polymers[<\/sup>2<\/a><\/sup>]<\/sup> and crucial energy storage system components.[<\/sup>3<\/a><\/sup>]<\/sup> Typical requirements for these applications include high surface area, low density, high porosity, desired surface chemistry (for instance to ensure wettability or suitable adsorption sites), good electrical conductivity, and mechanical properties.[<\/sup>4<\/a><\/sup>]<\/sup> High surface area carbon alternatives can also be produced by carbonization of resorcinol formaldehyde resins, aerogels or similar.[<\/sup>5<\/a><\/sup>]<\/sup> Carbon manufacturing is varied and can utilize chemical vapor deposition, arc discharge, laser ablation, pyrolysis, activation, or graphitization processes.[<\/sup>6<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

Most carbons used in materials science applications are fossil derived: carbon black, which is commonly used in tires, is typically derived from the incomplete combustion of heavy petroleum products,[<\/sup>7<\/a><\/sup>]<\/sup> most carbon fibers used in composites are polyacrylonitrile (PAN)- or pitch-based[<\/sup>8<\/a><\/sup>]<\/sup> and graphene and carbon nanotubes (CNTs) often use fossil-derived feedstocks.[<\/sup>9<\/a><\/sup>]<\/sup> Consumer perception and regulation are, however, currently driving demand towards non-fossil derived carbons.[<\/sup>10<\/a>, 11<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

The most common origins of non-fossil-derived carbons are ligno\/cellulosic materials: wood,[<\/sup>12<\/a><\/sup>]<\/sup> plant-based fibers from cotton, hemp, flax or coir[<\/sup>13<\/a><\/sup>]<\/sup> and bacterial cellulose[<\/sup>14<\/a><\/sup>]<\/sup> can be used as templates to produce carbon networks. An example of a successful non-fossil commercial carbon is YP-50F (Kuraray),[<\/sup>15<\/a><\/sup>]<\/sup> which is made from carbonized and activated coconut shell and is commonly used in supercapacitors. Research on creating carbons from biomass templates is typically directed towards either biomass with naturally organized structures, such as wood, grass and nutshell, or non-structured raw materials, such as sucrose, pitch and plastics using hard-\/soft-template methods, hydrothermal carbonization, chemical vapor deposition, spray pyrolysis or autogenic pressure carbonization.[<\/sup>6<\/a><\/sup>]<\/sup> Recent studies also emphasize the use of by-products and waste streams, such as creation of activated carbon using swine manure as a precursor[<\/sup>16<\/a>, 17<\/a><\/sup>]<\/sup> and porous carbons created from meat-processing industry by-products, such as bones, skin and scales.[<\/sup>18<\/a><\/sup>]<\/sup> Abundant plastic waste has also aroused interest as a precursor for carbons through co-pyrolysis with biomass, such as pinewood or sugar cane, and has the advantage of increasing surface area and improving discharge capacity in graphitic carbons.[<\/sup>19<\/a><\/sup>]<\/sup> Additional efforts have been made to utilize biomass pyrolysis vapors, which can be achieved using a calcium citrate template.[<\/sup>20<\/a><\/sup>]<\/sup> Key limitations of lignocellulosic material as carbon precursor are low yields (up to 30%),[<\/sup>21<\/a><\/sup>]<\/sup> energy- or chemical-intensive processing to reduce fiber sizes to the desired range[<\/sup>22<\/a><\/sup>]<\/sup> and resource competition (e.g., food, land, or water use).[<\/sup>23<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

Filamentous fungi represent a high potential yet underexplored template for producing carbon networks with key advantages over plant-based templates. Their filamentous growth inherently ranges from micro- to nanoscale in size depending on the species,[<\/sup>24<\/a><\/sup>]<\/sup> which is well suited to the production of carbon without requiring further size reduction or processing. Fungal networks often exhibit intricate and hierarchical porous structures, which could lead to carbons with unique porosities and surface areas. Species- and growth environment-influenced differences in fungal filament networks could further facilitate tuning to achieve custom-designed carbon structures.[<\/sup>25<\/a><\/sup>]<\/sup> This is augmented by the ability of fungi to up-concentrate and biomineralize inorganic matter,[<\/sup>26<\/a><\/sup>]<\/sup> which has been shown to be useful for applications in energy storage systems.[<\/sup>27<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

Fungal carbon templates are abundantly available as residual fungal biomass, such as spent mushroom substrate and mycelium waste[<\/sup>28<\/a><\/sup>]<\/sup> and consequently likely much cheaper than bacterial cellulose or other plant-based templates. Fungi-based food and biotechnology (enzymes, biofuels, or organic acids) industry by-products and wastes are available in volumes >170 million tons per year (5 kg of spent mushroom substrate is generated for every 1 kg of mushrooms produced)[<\/sup>29<\/a>, 30<\/a><\/sup>]<\/sup> that is normally downcycled into compost, animal feed or utilized for biogas production. Fungal biomass is also more rapidly producible than most plant-based templates through industrial fermentation processes,[<\/sup>31<\/a><\/sup>]<\/sup> which also do not compete with food production or land use. The use of fungal biomass as a template for creating carbons has, however, been almost completely neglected.<\/p>\n\n\n

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SEM micrographs and atomic force microscopy topographies for carbon derived from fungi \u00a9 TU Vienna<\/figcaption><\/figure><\/div>\n\n\n

We investigated fungal biomass as a template for a carbon network. Fungal fruiting bodies served as a model for an isolated source of fungal filaments that could be carbonized to characterize this individual, high-potential component of a spent mushroom substrate. Thermal degradation, elemental composition, morphology, physical and chemical properties of the fungal carbon network were assessed in addition to the electrical conductivity and potential for the manufacture of supercapacitor electrodes.<\/p>\n\n\n\n

2 Results and Discussion<\/h3>\n\n\n\n
<\/div>\n\n\n\n

2.1 Thermal Degradation Properties of Fungal Fruiting Bodies<\/h3>\n\n\n\n

L. edodes<\/em> and A. auricular-judae<\/em> fungal fruiting bodies exhibited a three-stage degradation process, while A. bisporus<\/em>and P. eryngii<\/em> exhibited further degradation at temperatures exceeding \u2248800 \u00b0C, likely due to the partial decomposition of solid carbon oxides (Table 2<\/a>) into CO2<\/sub> and\/or CO.[<\/sup>32<\/a><\/sup>]<\/sup> All fungal materials exhibited an onset temperature of thermal degradation of \u2248200\u2013230 \u00b0C, which was in line with previously reported literature values for fungal biomass[<\/sup>33<\/a>, 34<\/a><\/sup>]<\/sup>(Figure<\/strong> 1<\/a>). A. auricular-judae<\/em> exhibited the highest char residue (27.5 wt%) and lowest inorganic content (4.9 wt%) indicating the potentially greatest fungal carbon yield. L. edodes<\/em> also exhibited a high char residue (23.5 wt%) and low inorganic content (6.5 wt%). However, both A. bisporus<\/em> and P. eryngii<\/em> exhibited high inorganic contents (10.6 wt% and 12.4 wt%, respectively) and char residues of 18.2 wt% and 24.2 wt%, respectively.<\/p>\n\n\n

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\"Details<\/a>
Figure 1<\/strong>: Thermograms of fungal fruiting body powders in nitrogen and air atmospheres.<\/figcaption><\/figure><\/div>\n\n\n

2.2 Elemental Analysis of the Fungal Carbon<\/h3>\n\n\n\n

All fungal char exhibited high C (EDS: \u224843-67 at% and etched XPS: \u224858-70 at%) and O (EDS: \u224817-37 at% and etched XPS: \u224818-25 at%) content (Tables<\/strong> 1<\/a> and 2<\/a>).Table 1. Energy dispersive X-ray spectroscopy (EDS) of fungal fruiting body powders pyrolyzed using thermogravimetric analysis (TGA).<\/p>\n\n\n\n

<\/td>C<\/th>O<\/th>Mg<\/th>P<\/th>Cl<\/th>K<\/th><\/tr><\/thead>
Agaricus bisporus<\/em><\/td>67.2<\/td>16.8<\/td>0.3<\/td>3.3<\/td>1.0<\/td>11.6<\/td><\/tr>
Auricularia auricular-judae<\/em><\/td>43.2<\/td>36.7<\/td>0.4<\/td>1.9<\/td>0.1<\/td>17.7<\/td><\/tr>
Lentinula edodes<\/em><\/td>64.9<\/td>19.8<\/td>0.5<\/td>3.7<\/td>0.0<\/td>11.1<\/td><\/tr>
Pleurotus eryngii<\/em><\/td>62.0<\/td>20.6<\/td>0.7<\/td>5.2<\/td>0.0<\/td>11.5<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Table 2. Etched X-ray photoelectron spectroscopy (XPS) of fungal fruiting body powders pyrolyzed using TGA.<\/p>\n\n\n\n

<\/td>C<\/th>O<\/th>N<\/th>P<\/th>S<\/th>Cl<\/th>Si<\/th>K<\/th>Ca<\/th>Mg<\/th>Na<\/th><\/tr><\/thead>
Agaricus bisporus<\/em><\/td>67.6<\/td>20.1<\/td>1.5<\/td>3.8<\/td>0.4<\/td>0.1<\/td>0.0<\/td>5.9<\/td>0.3<\/td>0.3<\/td>0.1<\/td><\/tr>
Auricularia auricular-judae<\/em><\/td>59.2<\/td>24.8<\/td>1.8<\/td>1.6<\/td>0.2<\/td>0.2<\/td>0.9<\/td>5.5<\/td>2.1<\/td>1.5<\/td>2.3<\/td><\/tr>
Lentinula edodes<\/em><\/td>70.4<\/td>18.3<\/td>1.8<\/td>2.0<\/td>0.1<\/td>0.2<\/td>0.2<\/td>6.3<\/td>0.2<\/td>0.5<\/td>0.0<\/td><\/tr>
Pleurotus eryngii<\/em><\/td>57.8<\/td>24.8<\/td>1.7<\/td>4.2<\/td>0.8<\/td>0.2<\/td>0.0<\/td>8.8<\/td>0.5<\/td>1.3<\/td>0.1<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The C content of fungal char was considerably lower than that of typical carbon-based micro- and nano-reinforcements, such as carbon fibers (typically 92\u201399% C),[<\/sup>35<\/a><\/sup>]<\/sup> carbon black (typically >97% C),[<\/sup>36<\/a><\/sup>]<\/sup> graphene (almost 100% C)[<\/sup>37<\/a><\/sup>]<\/sup> and CNTs (typically almost 100% C).[<\/sup>38<\/a><\/sup>]<\/sup> The lower C content of fungal chars could negatively affect their mechanical, thermal, and electrical properties and suitability as composite reinforcement or filler by disrupting the carbon lattice structure or reacting with the matrix.[<\/sup>39<\/a>, 40<\/a><\/sup>]<\/sup> However, the composition and surface area of the fungal chars may render them useful as absorbents\/adsorbents.[<\/sup>41<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

All fungal carbons also exhibited considerable potassium content (EDS: \u224811-18 at% and etched XPS: \u22486-9 at%) and some phosphorus (EDS: \u22481-9 at% and etched XPS: \u22486-9 at%). P. eryngii<\/em> and A. bisporus<\/em> carbons, which exhibited the highest P contents in both EDS (5.2 at% and 3.3 at%, respectively) and XPS (4.2 at% and 3.8 at%, respectively) also exhibited the highest inorganic content post pyrolisis (12.4 wt% and 10.6 wt%, respectively) while A. auricular-judae<\/em>and L. edodes<\/em> carbon, which had the lowest P content in both EDS (1.9 at% and 3.7 at%, respectively) and XPS (1.6 at% and 3.0 at%, respectively), exhibited the lowest inorganic content post pyrolisis (4-9 wt% and 6.5 wt%, respectively). Phosphorus plays an active role in fungal metabolism[<\/sup>42<\/a><\/sup>]<\/sup> and can be incorporated into char as inorganic salts, such as potassium phosphate or potassium carbonate, during thermal decomposition.[<\/sup>43<\/a><\/sup>]<\/sup> The inorganic fraction may consequently comprise P inorganic salts. Nitrogen was also present in all fungal carbons (etched XPS: \u22482 at%). In addition to the noted elements, A. auricular-judae<\/em> carbon also contained \u22482 at% Ca, Mg and Na, also likely present as inorganic salts that may have been biomineralized into the hyphae from the substrate as reported in studies investigating the production of nanopapers from mycelial biomass grown on molasses.[<\/sup>26<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

The presence of inorganic salts in the fungal char did reduce the carbon content. However, P inorganic salts do have the potential to work as a flame retardant in composites[<\/sup>44<\/a><\/sup>]<\/sup> and enhance the absorption capacity for specific contaminants or pollutants by promoting favorable interactions between the absorbent material and target substance.[<\/sup>45<\/a><\/sup>]<\/sup> Potassium inorganic salts can also potentially promote the formation of stable carbon structures during the manufacturing process, which can also improve absorption capacity.[<\/sup>46<\/a><\/sup>]<\/sup><\/p>\n\n\n\n

2.3 Structural Analysis of the Fungal Carbon<\/h3>\n\n\n\n

XRD suggested that all samples comprised two types of crystalline content (Figure<\/strong>\u00a02a<\/a>). Silica (SiO2<\/sub>) was present in all samples with quartz dust (2\u03b8 = 35\u00b0) also present on the surface. Potassium bicarbonate (KHCO3<\/sub>, 2\u03b8<\/em>\u00a0= 23\u00b0) appeared to be the primary phase in\u00a0A. auricular-judae<\/em>\u00a0and\u00a0L. edodes<\/em>\u00a0carbons. An amorphous halo was also noted in the diffractograms, associated with the presence of black carbon, which typically occurs as crystals approximately several nm in size. Subtraction of the nanocrystalline black carbon halo from the diffractogram reveals crystalline peak shapes, which can be assigned phased using Rietveld refinement (Figure\u00a0S1<\/a>\u00a0and Tables\u00a0S1\u2013S4<\/a>, Supporting Information).<\/p>\n\n\n\n

<\/p>\n\n\n\n

…<\/strong><\/p>\n\n\n\n

<\/p>\n\n\n\n

You may read the complete report under https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1002\/gch2.202300315<\/a><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Abstract Carbons form critical components in biogas purification and energy storage systems and are used to modify polymer matrices. The environmental impact of producing carbons has driven research interest in biomass-derived carbons, although these have yield, processing, and resource competition limitations. Naturally formed fungal filaments are investigated, which are abundantly available as food- and biotechnology-industry […]<\/p>\n","protected":false},"author":59,"featured_media":142371,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"none","nova_meta_subtitle":"Scientists are using carbon filaments from mushrooms in supercapacitors, paving the way for a sustainable energy future","footnotes":""},"categories":[5572],"tags":[5838,5842,15106,19092,12690],"supplier":[20365],"class_list":["post-142367","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bio-based","tag-bioeconomy","tag-biomass","tag-filaments","tag-fungalmycelium","tag-lignocellulosics","supplier-vienna-technical-university"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/142367","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=142367"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/142367\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media\/142371"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=142367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=142367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=142367"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=142367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}