Highly durable non-platinum catalyst for protic ionic liquid based intermediate temperature PEFCs

Abstract

We firstly report remarkable stability and performance of non-precious catalyst, nitrogen doped graphene (NG) towards oxygen reduction reaction (ORR) in a protic ionic liquid (N,N-diethylmethylammonium trifluoromethane-sulfonate(dema-TfO)) at intermediate temperatures. Our electrochemical results indicate that an elevated operating temperature has an enhancing effect on ORR activity of NG in dema-TfO. In addition, even after 2000 cycles of potential sweep in the potential range from 1.0 V to 1.5 V vs. RHE at 120°C in dema-TfO, NG keeps the same ORR onset potential with 14% decrease in oxygen reduction current, showing the excellent stability of NG. Whereas commercially available Pt/C (Pt 37.5% in weight) shows 13% negative ORR onset potential shift along with 56% loss of oxygen reduction current during the stability test. TEM and EDS observations taken after durability test were also in agreement with the higher durability of NG over Pt/C at 120°C in dema-TfO. Raman and XPS results taken after the durability test also substantiated the structural stability of NG in dema-TfO at intermediate temperatures. The greater durability and comparable electrochemical activity of NG with Pt/C can unfold the possibilities of non-precious catalyst for intermediate temperature PEFCs.