Application Cases

Experiment Name: Application of High-Voltage Amplifier in Electrochemical Preparation of Graphene

Research Direction: Graphene

Testing Equipment: ATA-2021H Power Amplifier, Graphene Electrochemical Preparation Instrument, Signal Generator

Figure: Graphene Electrochemical Reaction Setup

Experimental Content:
The electrochemical method for graphene involves electrolyzing graphite in a mixture of ionic liquid (IL) and water, ultimately producing graphene with improved dispersibility due to IL functionalization. Generally, the preparation of graphene by electrolysis is mainly divided into two methods: anodic oxidation and cathodic reduction.

Anodic oxidation exfoliation for graphene preparation uses graphite as the anode. During operation, anions in the electrolyte migrate toward the anode and intercalate into the anodic graphite, causing volume expansion due to intercalation. When the volume of the anodic graphite increases to a certain extent, the interlayer van der Waals forces decrease, eventually leading to exfoliation from the bulk material. This forms layered graphene or graphene oxide (including single-layer and few-layer graphene oxide with 2–10 layers) containing certain oxygen-containing functional groups. During electrolysis, water at the anode partially decomposes to generate oxygen, which also enters the graphite interlayers. The combined action of these processes causes dramatic volume expansion of the graphite and eventual exfoliation from the surface.

Experimental Procedure:
Graphite anodic oxidation exfoliation method using graphite flakes as the anode, Pt as the cathode, and potassium sulfate and potassium hydroxide as the electrolyte.

Experimental Materials:

• 100 ml deionized water

• 2.4 g 98% H₂SO₄

• 4.7 g 30% KOH

Specific Experimental Steps:
(1) Solution Preparation. Clean the electrodes and glass containers. First, weigh 4.7 g of solid KOH to prepare a 30% mass fraction solution. After calculation, take 11 ml of water, add the KOH solid, and stir until dissolved. Then, weigh 2.4 g of 98% H₂SO₄ solution and pour it together with the KOH solution into 100 ml of deionized water. The solution is now prepared.

(2) Power Configuration. Connect one end of copper wires to the cathode and anode electrode materials. Then, place the electrodes into the prepared solution. Connect the other ends of the copper wires to the positive and negative terminals of a DC regulated power supply, respectively. Set the signal generator to output a square wave with a peak voltage of 1.6 V. Connect the signal generator to the power amplifier with an amplification factor of approximately ×16 to obtain a ±15 V square wave. Control the temperature at 25°C and turn on the power.

(3) Equipment Connection. Connect the power amplifier signal to the electrodes; the two electrodes are the graphite flake and Pt.

(4) Cleaning the Graphene Solution. The electrochemical reduction reaction time is 10 minutes. After waiting for the graphite to exfoliate, the generated graphene solution (strongly alkaline) is cleaned by centrifugation, repeatedly washing with deionized water.

Experimental Results:

Figure: Characterization of Graphene Dispersion

The characterization of graphene dispersions requires electron microscopy. The above figure shows TEM characterization images of the graphene dispersion at different scales. These images reveal the nanostructural features of the electrochemically exfoliated graphene. In Figure (b), a selected diffraction boundary region is magnified in Figure (c), where it can be observed that the graphene layers number 6–8, indicating that this graphene sample is few-layer graphene (fewer than 10 layers). Figure (d) is a high-resolution image showing a hexagonal lattice structure with a honeycomb pattern, demonstrating the excellent structural properties of the graphene material prepared by this method.

Figure: ATA-2021B High-Voltage Amplifier Specifications and Parameters