Binder/conductive additives matrix

High electronic conductivity to obviate the need for additional conductive materials in the electrode. Additives are often used in composite electrodes to enhance conductivity, to act as binders, or as clectrochemically inactive matrixes that attenuate the mechanical stress resulting from the volume variation of the insertion material during the insertion-deinscrlion processes. 

The essential ingredients of the catalyst layer are an electronically conducting matrix of carbon grains, Pt catalyst particles supported on carbon and a protonconducting network of well-humidified PFSI. In addition, Teflon (PTFE) may be added as a binder and hydrophobizing agent. 

The catalyst ink usually includes catalyst, carbon powder, binder, and solvent. Sometimes, other additives are added to improve the dispersion of the components and stabilize the catalyst ink. The catalyst either covers the surface of the GDL or directly coats the surface of the membrane (catalyst coated membrane, CCM). The CL usually consists of (1) an ionic conductor such as perfluorosulfonate acid (PFSA) ionomer to provide a passage for protons to be transported in or out, (2) metal catalysts supported on a conducting matrix like carbon, to provide a means for electron conduction, and (3) a water-repelling agent such as polytetrafluoroethylene (PTFE) to provide sufficient porosity for the gaseous reactants to be transferred to catalyzed sites [5, 6]. Every individual factor must be optimized to provide the best overall performance of a CL. 

V2O5 can also form composites with conductive polymers such as polyaniline (PAn), PPy, and pol5dhiophene (PTh). These polymers increase electronic conductivity. In addition, there is some static charge interaction between the conductive polymers and the V2O5 matrix. Finally, the polymers can act as a binder. As a result, the electrochemical performance of these composites is quite good. 

---