Study on the electrodissolution and roughening of a palladium electrode in chloride containing solutions

Potential-dependent surface electrooxidation processes of a Pd electrode in chloride containing solutions have been investigated in detail by means of in situ confocal Raman spectroscopy for the first time. In a solution of HCl, characteristic Raman bands for the oxidative coordination of Pd with Cl−, the transformation of soluble Pd(II) to Pd(IV) complexes, the electrooxidation of Cl− into Cl2, and the redox between Cl2 and Pd were all detected unambiguously during the potential ascending. While in a solution of KCl, insoluble salt films of K2PdCl4 and K2PdCl6 were found on the electrode surface due to their poor solubility. Moreover, electrochemical roughing of Pd electrode by electrodissolution–electrodeposition cycling in the HCl solution with a surfactant have been utilized to construct micro-nanostructures of Pd, which display high activity toward the electrooxidation of ethanol in an alkaline medium and obvious surface enhanced Raman spectroscopy (SERS) signals for pyridine probe molecules.