Synthesis and Characterization of PANI-MWCNTs Supported Nano Hybrid Electrocatalysts

Among new energy systems, fuel cells are electrochemical devices transforming chemical energy directly into electrical energy. In our previous works, MWCNTs (the multi walled carbon nanotubes) supported palladium anodic electrocatalysts for DFAFCs (direct formic acid fuel cells) have been studied. MWCNTs can be modified by appropriate oxides, for example, cerium oxide, zirconium oxide and N-doped titanium dioxide, to enhance the electrocatalytic performance of the catalysts. But the oxides and the defects of the acid oxidized MWCNTs, denoted as AO-MWCNTs, can cause the electron capture and reduce both the catalyst conductivity and the catalysts activity. In order to improve the conductive properties of the support, in the present work a conductive polymer was introduced to modify the surface of carbon nanotubes. PANI (polyaniline) has a long-chain structure and conjugated structure and exhibits good conductivity, high stability, and is non-toxic. After PANI modification, AO-MWCNTs can provide efficient electronic conduction network. In this study, PANI modified AO-MWCNTs were prepared via polymerization process. AO-MWCNTs were homogeneously coated with PANI to obtain composite with weight ratio 50:50 PANI to MWCNTs. The thickness of the PANI layer was 4-9 nm. It was shown that the photosynthesis process is a better method to reduce Pd on PANI/AO-MWCNTs than by using NaBH4. By adjusting pH value to 9, during preparation of Pd/PANI/AO-MWCNTs composites by X-ray irradiation process, smaller Pd particles were obtained and PANI deprotonation was avoided which explains better activity of this composite in formic acid electro oxidation.