Nano crystalline porous silicon as large-area electrode for electrochemical synthesis of polypyrrole

Polypyrrole (pPy) films were electrochemically synthesized over the surface of nano-crystalline porous silicon (pSi), platinum (Pt) and polished silicon (Si) substrates. As evidenced by the SEM pictures and the potential time-transient characteristics the polymerized growth is relatively porous, smooth and faster over pSi substrates in comparison to the Pt and polished Si surfaces. The polymerization charge on pSi substrate is significantly enhanced and the high accessible surface area of nano-pSi/pPy structure resulted in an improved redox performance of pPy. Impedance study revealed no change in the diffusion control process for pSi/pPy and Pt/pPy electrodes whereas an increase in Faradaic resistance for pSi/pPy electrode is noticed. Redox properties of pPy on n- and p-type pSi structures were studied using cyclic voltametry and electrochemical impedance spectroscopy. FESEM was used to study the surface morphology and to further compliment the electrochemical performance of the electrode. (c) 2006 Elsevier B.V. All rights reserved.