Cu@NC as high-performance and durable electrocatalyst for oxygen reduction reaction in alkaline membrane fuel cells

Abstract

Discovery of electrocatalysts composed of cheap transition metals are urgent to replace the traditional Pt/C catalyst used for oxygen reduction reaction (ORR). Herein, we synthesized Cu nanoparticles encapsulated with nitrogen-doped carbon (Cu@NC) as an excellent and durable catalyst for ORR. A systematic evaluation of the effect of Cu content, acid leaching and secondary heat treatment have been established with the help of half-cell studies. The morphological analysis revealed that Cu nanoparticles surrounded by thick nitrogen doped carbon layers and further, the acid leaching and subsequent pyrolysis, boosted the electrocatalytic performance. The optimized Cu@NC catalyst showed onset potential (potential corresponding to a current density of 0.10 mA cm−2) and half-wave potential of 0.97 V vs. RHE and 0.85 V vs. RHE, surpassing the state-of-the-art Pt/C catalyst. In addition, the Cu@NC catalyst exhibited outstanding durability, tolerance to carbon monoxide and methanol molecules. In the alkaline fuel cell, Cu@NC catalyst delivered 118 mW cm−2 peak power density in alkaline fuel cell operated with H2-O2, whereas Pt/C only delivered a peak power density of 97 mW cm−2 under ambient operating conditions. High ORR activity and better stability of Cu@NC catalyst could be a potential alternative to Pt/C catalyst in alkaline fuel cells and metal-air cell cathodes.