Noble Metal-Free Oxidative Electrocatalysts: Polyaniline and Co(II)-Polyaniline Nanostructures Hosted in Nanoporous Silica (original) (raw)

Electrocatalysts that are capable of catalyzing oxidation of organic compounds have enormous appeal because of their potential applications in fuel cells as well as organic syntheses. [ 1 , 2 ] Moreover, when used in chemical reactions for organic synthesis, oxidation electrocatalysts have advantages compared to conventional oxidation catalysts because the former enable 'greener' processes by avoiding the use of sacrifi cial oxidizing agents that often lead to undesired byproducts. [ 3-5 ] However, despite these potential advantages, the use of electrochemical catalysts in oxidation reactions for synthetic purposes is not a very well explored research fi eld. On the other hand, in the past few years, a number of fuel cells based on oxidative electrocatalytic systems have been designed and demonstrated to work using methanol, [ 6-9 ] methane, [ 10 , 11 ] ethanol, [ 12 , 13 ] hydrazine, [ 14 , 15 ] formic acid [ 16 , 17 ] and L-ascorbic acid [ 18 , 19 ] as fuels. However, in all of these cases, high effi ciency in the fuel cells was obtained only when expensive noble metal and bimetallic nanoparticles such as PtRu and PtSn supported on carbon were used as the electrocatalysts. [ 20 , 21 ] Furthermore, most of these nanoparticle-based electrocatalysts have been known to easily aggregate or quickly get poisoned by the oxidation reaction products and thus lose their electrocatalytic activities in the presence of reactants/products. [ 22 , 23 ] Moreover, many of these electrocatalysts do involve expensive and precious metals such as Pt, Au, Pd and Ru. [ 24 , 25 ] We here propose and demonstrate successfully a new in situ synthetic method to highly active oxidation electrocatalysts that are composed of electroactive/conducting polyaniline (PANI) nanostructures that are controllably polymerized within the channels pores of mesoporous silica. There are clearly some benefi ts and advantages to be expected by confi ning or synthesizing PANI within the pores of the high surface area mesoporous silica materials such as SBA-15. This is also supported, to some extent, by experimental results in our case (see below). Generally, when polymers such as PANI are prepared as bulk