EP-4740251-A2 - MANUFACTURE OF POPCORN GRAPHITE ELECTRODES FOR ELECTRONICS AND BIOELECTRONICS

Abstract

An electrode comprising a self-supporting porous structure of expanded graphite and an electrical connector. Method for manufacturing a self-supporting porous structure of expanded graphite, said method comprising the following steps: preparing a suspension of expanded graphite particles in a liquid; sonicating said suspension of graphite particles by applying ultrasound, to obtain a homogenized suspension; and filtering said homogenized suspension under pressure to obtain an expanded porous structure which is at least partially and preferably substantially dry.

Inventors

• HOLZINGER, Michaël
• MOHANTY, ANURAG
• GROSS, ANDREW

Assignees

• Centre National de la Recherche Scientifique
• UNIVERSITÉ GRENOBLE ALPES

Dates

Publication Date

20260513

Application Date

20240705

Claims (10)

1. 1. An electrode comprising a self-supporting porous structure of expanded graphite and an electrical connector.
2. 2. The electrode of claim 1, wherein said self-supporting porous structure of expanded graphite comprises expanded graphite flakes.
3. 3. The electrode according to any one of claims 1 or 2, wherein said electrode comprises at least one catalyst for an oxidation or reduction reaction.
4. 4. The electrode of claim 3, wherein said catalyst is adsorbed by said self-supporting porous structure of expanded graphite.
5. 5. The electrode according to any one of claims 3 or 4, wherein said catalyst is selected from the group consisting of metal catalysts, such as platinum, and biocatalysts, such as enzymes, and in particular enzymes for the oxidation of glucose or the reduction of oxygen.
6. 6. Method for manufacturing a self-supporting porous structure of expanded graphite, said method comprising the following steps: a) preparing a suspension of expanded graphite particles in a liquid; b) sonicating said suspension of graphite particles by applying ultrasound, to obtain a homogenized suspension; c) filtering said homogenized suspension under application of a vacuum to obtain a self-supporting porous structure of expanded graphite which is at least partially and preferably substantially dry.
7. 7. Method according to claim 6, wherein a step of expanding expandable graphite particles is carried out beforehand.
8. 8. A method according to claim 6 or 7, wherein said expanded graphite particle dispersion has an expanded graphite particle concentration of between 0.5 mg.mL' 1 and 10 mg.mL' 1 , and preferably 1.5 mg.mL-1 ± 0.5 mg.mL-1.
9. 9. A method according to any one of claims 6 to 8, wherein said liquid is an organic compound selected from the group consisting of N-methyl-2-pyrrolidone, dichloromethane, acetonitrile, 1,3-dioxolane, dimethylformamide, and mixtures of two or more thereof, and preferably toluene.
10. 10. Use of an electrode as described in claims 1 to 5 in an energy storage and/or recovery device, such as batteries, supercapacitors or fuel or hydrogen biocells, an electronic or bioelectronic device, a biosensor, a biodetector, a bioreactor, or a biocatalyst.

Description

Description Title: Fabrication of popcorn graphite electrodes for electronics and bioelectronics [0001] Field of the invention [0002] The present invention relates in particular to the field of electrode materials for manufacturing catalytic electrodes and/or enzymatic bioelectrodes for use in glucose biosensors and fuel biocells. This invention relates in particular to the development of porous structures of microwave-expanded graphite ("popcorn graphite" paper) from expandable graphite flakes, and their use for preparing electrodes such as, for example, enzymatic bioelectrodes. [0003] Description of the prior art [0004] Bioelectrodes (bioanodes and biocathodes) are often formed by immobilizing enzymes and redox molecules on the electrode that enable bioelectrocatalysis. Current methods do not use graphite for bioelectrode applications. Carbon nanotubes and graphene or graphene oxide-related nanoscale materials are mainly used and are more expensive. [0005] Expandable graphite, initially called graphite salts, has been known since the beginning of the last century. This expandable graphite is obtained by heat treatment of mineral graphite with strong inorganic acids such as sulfuric acid and oxidants such as persulfuric acid or hydrogen peroxide [1-3]. These powerful agents transform the pore structure to increase the specific surface area of the mineral graphite. These agents, including sulfuric acid, have the ability to intercalate between the graphene sheets during this treatment, which makes it possible to obtain expandable graphite, such as graphite sulfate C24( HSO4 )( H2SO4 )2. The expansion is initiated by heat treatment (>200°C) or by microwave (800W) which leads to the spontaneous evaporation of the agent and to [partial exfoliation of the different graphene layers. This phenomenon immediately causes a considerable increase in the volume of the material, like the formation of popcorn from grains. This expanded graphite, or "popcorn", has been used for decades in composite materials as flame retardants [4] and as additives for heat and energy storage [5], Graphite Expanded graphite can be processed into sheets by calendering processes or extruded into composites for various applications. Expanded graphite has regained the attention of scientists because it can be an excellent precursor for the large-scale synthesis of high-quality single-layer graphene [6] by calendering. [0006] There are disclosures on the use of expanded graphite as a metal catalyst support in alcohol fuel cells for electrocatalytic reduction of oxygen and oxidation of alcohols [7, 8, 9], Expanded graphite composites are also used in the energy conversion sector for heat conduction, gas diffusion and electron collectors (called bipolar plates in hydrogen fuel cells). Expanded graphite is also mentioned as an anode material in a microbial (and not enzymatic) fuel cell [10], [0007] However, when it comes to enzymatic biofuel cells, carbon nanotubes are the material of choice due to their advantageous structure (e.g., high surface area and attractive porous and conductive structure), their inertness, and the possibility of forming self-supporting macroscopic electrodes in different forms: films, papers, and pellets [11, 12]. Thus, carbon nanotube-based enzymatic biofuel cells produce 2 to 3 orders of magnitude more energy than similar graphene-based biofuel cells [11, 13]. However, developments of carbon nanotube-based enzymatic biofuel cells have remained at the academic level with few exceptions due to the cost of this material (see above) and its potential and/or presumed toxicity [14, 15]. Thus, as of January 2020, companies that manufacture or import nanoscale materials such as carbon nanotubes (CNTs) will be subject to additional legal requirements under the REACH regulation (https://echa.europa.eu/regulations/nanomaterials). Where less porous materials are used, for example, glassy carbon or graphene, these are generally limited in terms of catalytic efficiency/voltage. [0008] There therefore remains a need to obtain very inexpensive porous carbon-based electrodes which are advantageously more efficient than most materials available in the industry and/or which present a substantially reduced toxicological risk. Technical description of the invention [0009] It has thus been determined that the use of expanded graphite in the form of a self-supporting porous structure (in particular in the form of paper, sheets, plates, discs or pellets) based on very cheap carbon is more effective than most materials available in the industry. The term "self-supporting" is equivalent to the term "self-supporting" and indicates that the material is in a form capable of ensuring its own span from one support point to another without intermediate support in particular at room temperature and atmospheric pressure. The term "self-supporting structure" is therefore understood in macroscopic space and relates to a structure advantageously having