Expanded Graphite Exfoliation for Low-Waste Graphene Oxide
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Solution Overview
Problem
Current methods for producing graphene-based nanomaterials from graphite are costly and generate significant chemical waste, limiting their scalability and environmental sustainability.
Innovation Solution
A process to produce expanded graphite from natural graphite powder without binders, followed by electrochemical exfoliation into graphene oxide using an aqueous electrolyte, involving steps like mixing with H2SO4/H3PO4, addition of KMnO4 and Fe(III) salt, and thermal treatment, then compressing and electrochemically exfoliating the graphite foil in an alkali metal hydroxide solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If current methods are used to produce graphene-based nanomaterials from graphite, then graphene can be produced, but the production is costly and generates significant chemical waste
Solution Approach 1:
The patent changes the chemical parameters of the oxidation process by using a modified Hummers method with specific ratios of H2SO4:H3PO4 (9:1 v/v), controlled addition rates of KMnO4, and optimized reaction temperatures (0-20°C during oxidation, then heated to 35-40°C). These parameter optimizations reduce chemical waste while maintaining high productivity in graphene oxide production
Solution Approach 2:
The patent employs strong oxidants including KMnO4 and NaClO in the oxidation process to efficiently convert graphite to graphene oxide. The use of these strong oxidants accelerates the reaction, reducing production time and chemical waste while maintaining high yield, directly addressing the contradiction between productivity and substance loss
2Object-generated harmful factors
If binder-free expanded graphite is produced, then environmental friendliness improves, but process complexity increases
Solution Approach 1:
The patent extracts and eliminates binders from the expanded graphite production process. By using a specific intercalation method with H2SO4/H3PO4 and KMnO4 that creates self-sustaining expansion through gas evolution (O2, CO2), the process achieves binder-free expanded graphite. This extraction of harmful binders reduces environmental impact while the automated gas-evolution mechanism keeps process complexity manageable
Solution Approach 2:
The oxidation and expansion process is designed to be self-sustaining through controlled gas evolution. The KMnO4 oxidation generates gases (O2, CO2) that automatically penetrate and expand the graphite structure without external intervention or binders. This self-service mechanism reduces environmental harm while avoiding the need for complex binder removal procedures
3Use of energy by moving object
If electrochemical exfoliation is used, then energy efficiency improves, but the method is limited to materials with weak interlayer forces
Solution Approach 1:
The patent applies preliminary chemical oxidation to convert graphite into graphene oxide with modified interlayer forces before electrochemical exfoliation. The oxidation process introduces oxygen functional groups that weaken interlayer van der Waals forces, making the material more susceptible to subsequent low-energy electrochemical exfoliation. This preliminary action enables energy-efficient processing while expanding adaptability to graphite-based materials
Solution Approach 2:
The patent changes the physical-chemical parameters of graphite by oxidizing it to graphene oxide, altering interlayer spacing and bonding characteristics. This parameter change enables the material to undergo electrochemical exfoliation at lower energies while maintaining versatility for energy storage applications. The oxidized state creates favorable conditions for energy-efficient exfoliation without limiting material applicability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method is energy-efficient, environmentally friendly, and produces stable graphene oxide without the need for organic solvents, enabling large-scale production of graphene-based nanomaterials for applications in energy storage and sensing.
Implementation Method 1
adding KMnO4 to the first mixture to form a second mixture... to form a solid graphite-intercalated compound
Implementation Method 2
adding at least one Fe(III) salt to the second mixture under conditions to form a solid graphite-intercalated compound
Implementation Method 3
heating the solid graphite-intercalated compound under conditions to provide the expanded graphite
Implementation Method 4
immersing the flexible graphite foil in a solution comprising at least one alkali metal hydroxide and optionally at least one oxidizing agent, and applying a voltage under conditions to electrochemically exfoliate the flexible graphite foil to provide the exfoliated graphene oxide
Data Source
AI summary
The present application relates to expanded graphite and exfoliated graphene oxide. More specifically, the present application relates to process for their preparation and uses thereof. The present application includes a process for preparing expanded graphite comprising: mixing graphite with H2SO4/H3PO4 to form a first mixture; adding KMnO4 to the first mixture to form a second and mixture; adding at least one Fe(III) salt to the second mixture under conditions to form a solid graphite-intercalated compound; separating the solid graphite-intercalated compound from the second mixture; and heating the solid graphite-intercalated compound under conditions to provide the expanded graphite. The present application also includes a process for preparing exfoliated graphene oxide comprising: compressing expanded graphite to form a flexible graphite foil; immersing the flexible graphite foil in a solution comprising at least one alkali metal hydroxide and optionally at least one oxidizing agent, and applying voltage under conditions to electrochemically exfoliate the flexible graphite foil to provide the exfoliated graphene oxide.