Performance characteristics for oxygen reduction reaction of nanostructured Pt100-xCox supported on Vulcan carbon andcarbon nanotubes catalysts

The catalytic activity for oxygen reduction reaction (ORR) of Pt100-xCox (100 ≥ x ≥ 0) catalysts supported on Vulcan carbon XC-72R (VC), raw carbon nanotubes (rCNTs) and purified carbon nanotubes (pCNTs) was investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The materials were synthesised by chemical reduction using NaBH4 as reducing agent. The TEM, XRD and XRF data were consistent with the formation of Pt-Co alloy nanoparticles having size ranging from 1.00 nm to 14.00 nm. The linear sweep voltammograms showed that Pt80Co20/VC, which has the least coverage of oxygenated species, was the best catalyst for ORR with its onset potential of 0.574 V. From the slope of Koutecky-Levich plots for ORR using Pt100-xCox/VC materials as catalysts, it was found that the overall electron transfer number ranged from 3 to 4, which led to the suggestion of H2O2 formation as an intermediate of the ORR. Carbon nanotubes after treatment (pCNTs) exhibited better activity for ORR compared to raw CNTs. However, Pt80Co20 catalyst supported on Vulcan carbon showed an enhancement in catalytic activity higher than that on CNTs; therefore, the replacement of CNTs to Vulcan carbon did not improve the performance of the catalysts.