NaOH‐Aided Platinum Nanoparticle Size Regulation on Polybenzimidazole‐Wrapped Carbon Nanotubes for Use as Non‐Humidified Polymer Electrolyte Fuel Cell Catalyst

Abstract

AbstractWe describe a method to control the size of platinum nanoparticles (Pt‐NPs) on poly[2,2′‐(2,6‐pyridine)‐5,5′‐bibenzimidazole] (PyPBI)‐wrapped pristine multi‐walled carbon nanotubes (MWNTs) without changing the loading amount by adding various concentrations of sodium hydroxide (NaOH) to the ethylene glycol aqueous solutions. The Pt‐NP sizes decreased from 3.8±0.4 to 1.7±0.1 nm with increasing NaOH concentrations. The mass activity of the oxygen reduction reaction was 224 mA mgPt−1 for the electrocatalyst with 3 nm Pt‐NPs, in which the power density reached 350 mW cm−2, which was 1.4 times higher than that of the electrocatalyst synthesized without NaOH (250 mW cm−2) at 120 °C and without any extra humidification. The electrocatalyst synthesized from a small amount of additional NaOH (0.5 mm) in the starting solution shows an enhanced performance and similar Pt stability. More importantly, the Pt‐NP size showed no effect on the Pt stability owing to the use of the PyPBI.