A recent theoretical study has shown that structural defects in graphene can significantly increase it selectron transfer rate, a result that could lead to improving the efficiency of electrochemical sensors. The effects were reportedby scientists from the Moscow Institute of Physics and Technology and the Russian Academy of Sciences Joint Institute for High Temperatures.
Because of its electrochemical properties, graphene is a desirable material for electrochemical sensor applications, such as biosensors, photovoltaics and more. Graphene’s electrochemical properties significantly depend on its chemical structure, and the new study looked at how these properties change with defective graphene.
"In our calculations, we tried to establish a relation between the kinetics of heterogeneous electron transfer and the changes in the electronic properties of graphene caused by defects,” said Sergey Kislenko of the Moscow Institute of Physics and Technology.
Instead, the team discovered that introducing defects into a graphene sheet accelerates electron transfer and increases the density of electronic states near the Fermi level.
Defective Graphene
Calculations show that structural defects in graphene can significantly increase the charge transfer rate. This is due to the fact that the graphene is affected by its chemical structure and electronic properties. Consequently, the kinetics of redox processes are affected by defects such as single and double vacancies, the Stone-Wales defect, nitrogen impurities, and epoxy and hydroxyl groups.
Of these defects, the single vacancy appears to be the most significant, in which charge transfer rate grows by an order of magnitude relative to defect-free graphene. This increase is related to redox processes with a standard potential of −0.2V to 0.3V relative to the standard hydrogen electrode.
By varying the type of defect in graphene, it ispossible to selectively catalyze the electron transfer to a certain class of reagents in the solution. This feature could be used to develop more efficient electrochemical sensors and electrocatalysts.
The researchers also predict that due to the graphene sheet’s low quantum capacitance, the electron transfer kinetics can be controlled by changing the bilayer’s capacitance. Graphene’s electrochemical properties depend on the defect type because of the electronic structure variances caused by defects.
Chemically modified graphene has great potential. It can be a cost-saving alternative to platinum or iridium catalysts in fuel cells and metal-air batteries. Graphene can also be used in carbon-based electrodes, with applications in biosensors, photovoltaics and electrochemical cells.