Electrochemical polymerization of acetylene on Rh electrodes probed by surface-enhanced Raman spectroscopy

By combining cyclic voltammetry (CV) and surface-enhanced Raman spectroscopy (SERS), the electrochemical behaviors of acetylene (C2H2) on a roughened Rh electrode in 0.1 M HClO4 solution were studied. On both roughened and smooth Rh surfaces, a clear loop in the cyclic voltammogram was observed in the negative potential region, indicating the formation of a new phase. However, only on the roughened Rh surface was the Raman signal of surface species observed. The resemblance of the detected signal to that of polyacetylene indicates the occurrence of polymerization of acetylene at potentials more negative than −0.3 V. The electropolymerization of acetylene is proceeded via an electrochemical radical addition assisted by hydrogen radical. A combined contribution of both the resonant Raman effect and especially surface-enhanced Raman effect may account for the observed signal.