The combination of electrochemical and spectroscopic techniques yields complementary information when studying (electro)chemical reactions.
Electrochemical techniques offer precise quantitation with the possibility to analyze solutions at the low part per million concentration range, or surface processes involving sub-monolayer coverages. The drawback of electrochemical methods is that they offer limited specificity for the target reaction. The information is rather one-dimensional as researchers can monitor the flow of electrons at a given potential, but it is difficult and often impossible to attribute the current signal to a single process.
Optical spectroscopic methods like Raman spectroscopy provide molecular information and the possibility to monitor chemical processes as they occur.