Investigation of Sulphates used in Graphene Electrochemical Exfoliation Production

This technique involves using a graphite anode and a carbon cathode in a solution of a sulphate.

Theory

Molecules of the sulphate are excited by the current and attracted to the anode. The sulphate ion is a polyatomic anion and penetrates between the graphite layers of the anode. As more molecules force their way in, a layer is eventually forced off the surface. This is known as exfoliation and produces large flakes.

Parameters

• The concentration of the sulphate
• The voltage supplied
• The cathode material

Materials

Each experiment used a 2l beaker with two clips holding the anode and cathode at opposite sides.

1200ml of the solutions listed below were used in turn as the electrolyte.

Sri Lankan vein graphite ore was used as the anode material and a standard 10mm diameter carbon rod was used as the cathode.

A variable power supply was connected and run at the voltages described in the table below.

An initial low voltage was applied to encourage migration over agitation and then increased to maximise the exfoliation and left until the majority of the effect had ceased.

Sulphate Solutions

Voltage Applied

Practice

The flakes produced are somewhat conductive and tend to float, so a short circuit is quickly made unless prevented. Plastic was initially used, but it was found that plain paper wrapped round the cathode works just as well.

Filtering

the contents of the beaker was filtered using a hand vacuum pump and rinsed using deionised water.

The recovered flakes were then dried by placing in an oven at 60c for 4 hours before being weighed (results in the Suspension Yield table below).

Sonication

The recovered flakes were ground in a pestle and mortar until a powder again (clumped after drying) and then added to a 1l beaker containing 600ml strong black tea.

The beaker was then placed in ultrasonic bath for 60 mins.

The resulting suspension was bottled and left for 5 days for any non suspended solids to settle.

The top liquid was decanted off and the remaining solids dried by placing in an oven at 60c for 4 hours and then weighed. The results and calculated suspension mass is detailed in the Suspension Yield table below.

Proviso

• New pieces of ore were used for each experiment and may vary in quality.
• Experiments took place over a number of days with differing temperature and humidity conditions.
• None of the equipment used has been formally calibrated.

Results

The table below shows the yield from each experiment:

Suspension Yield

Suspension Yield Chart

Observations

The following observations were made from the results:

• The average presumed suspension weight is 1.55g throughout all experiments.
• The yield trend shows almost level 60%, the average being 59.47%.
• Na2SO4 was the easiest to wash.