In order to avoid false or irreproducible results you should only measure the emf (without current flow) of an electrochemical cell completed with a typical reference electrode in a solution which contains an Ion which can pass the phase boundary to your composite electrode. Without any charge transfer species you will not get a reproducible emf. For serious data a potentiostat is a must. Drawing current through a reference electrode may damage it. But without using a difficult to polarize reference electrode it is not clear at which electrode which potential drop is created during current flowing through the electrochemical cell.

You may do electrochemical impedance initial characterization. You can apply a sinusoidal potential signal at known frequencies with an amplitude of 10-50mV with DC at the open circuit potential. Then record the generated current in known electrolyte with a counter electrode with a bigger surface area then your working electrode, and calculate the impedance. You can do that at different frequencies and generate the Bode and Nyquist plots. That will give you information on the double layer capacitance and charge transfer resistance.

Really, the best way to get reliable detailed electrochemical properties/characteristics of a new electrode material is to use a potentiostat/galvanostat. It is a pity your potentiostat is no longer working, but that is not the end of the world, you can build one yourself for $50-100. We have shown you how you can do this in the attached paper. If you are not familiar with electronics, I am sure your electronics staff can help you build this within a day.There are many other reported approaches for building potentiostats in the literature. Good luck!!!

Article Build Your Own Potentiostat