A phosphoric acid-doped electrocatalyst supported on poly(para-pyridine benzimidazole)-wrapped carbon nanotubes shows a high durability and performance

Abstract

Low fuel cell performance and durability are still the two main obstacles to the commercialization of high-temperature polymer electrolyte fuel cells. Herein, we have prepared a membrane electrode assembly (MEA) composed of a phosphoric acid (PA)-doped platinum electrocatalyst supported on poly[2,2′-(2,5-pyridine)-5,5′-bibenzimidazole] (para-PyPBI)-wrapped multi-walled carbon nanotubes (denoted MWNTs/para-PyPBI-PA/Pt), and PA-doped para-PyPBI as the electrocatalyst and the electrolyte membrane, respectively. The prepared MWNTs/para-PyPBI-PA/Pt showed a higher electrochemical stability against carbon corrosion compared to that of the conventional CB/Pt; namely, the initial electrochemical surface areas (ECSA) after 10 000 start-up/shutdown cycles (1–1.5 V vs. RHE) of these two electrocatalysts decreased by 20% and 47%, respectively. The power density of the MEA using the MWNTs/para-PyPBI-PA/Pt and PA-doped para-PyPBI measured at 120 °C with external humidification reached 414 mW cm⁻², which was approximately 2 and 2.5 times those of the non-PA doped electrocatalyst (208 mW cm⁻²) and conventional CB/Pt (167 mW cm⁻²). Meanwhile, under non-humidified operation, the mass power density reached 0.92 W mg_Pt⁻¹, which is very high for high-temperature PEFCs.