Effect of modification of multi-walled carbon nanotubes with nitrogen-containing polymers on the electrochemical performance of Pt/CNT catalysts in PEMFC

The influence of the surface modification of multi-walled carbon nanotubes (MWCNT) with nitrogen-containing compounds on the performance of 40 wt% Pt/MWCNT catalysts in the oxygen electroreduction reaction (ORR) was investigated using a rotating disk electrode (RDE) at 10–35 °C in 0.1 M HClO4 as electrolyte in electrochemical cell, and in a hydrogen–oxygen polymer electrolyte membrane fuel cell (PEMFC) at 82 °C. The catalysts were characterized by low-temperature nitrogen adsorption, XPS, TEM, gas-phase CO titration, electrooxidation of the adsorbed CO monolayer, and cyclic voltammetry. It was shown that the modification of MWCNT with melamine–formaldehyde resin leads to the surface nitrogen concentration up to 8.3 at.% (CNT-MF sample). The 40 wt% Pt/CNT-MF catalyst with 0.1 mg cm−2 Pt loading on the cathode showed a good performance in PEMFC (~ 0.61 W cm−2) and a high utilization ratio (0.84) of Pt in membrane electrode assembly as compared to Pt/CNT catalyst (~ 0.37 W cm−2 and utilization of 0.29). The higher power density of nitrogen-modified catalysts was ascribed to a higher utilization of Pt in the electrode layer.