Rich and uncovered FeNx atom clusters anchored on nitrogen-doped graphene nanosheets for highly efficient and stable oxygen reduction reaction

Abstract

It is still challenging but essential to synthesize non-noble catalysts with rich and uncovered catalytic active sites towards oxygen reduction reaction (ORR). And the limited research of the ORR properties of FeNx atom clusters also hinders their practical implementations. Here, we report a two-dimensional (2D) non-precious ORR catalyst constructed by abundant and fully exposed FeNx atom clusters anchored on nitrogen-doped graphene nanosheets (Fe-N-C/NG), which derives from three-dimensional (3D) ZIF-8, 2D graphene oxide nanosheet, and ferrocene. The optimized Fe-N-C/NG delivers outstanding ORR activities (Eonset = 0.97 V, E1/2 = 0.84 V, Jd = 5.48 mA cm−2), excellent Tafel slope (57.7 mV dec−1), remarkable long-term durability, and strong methanol tolerance in an alkaline electrolyte. Its superior catalytic activity is possibly attributed to its unique conversion of nanoarchitecture and the synergistic effects: the change of morphology effectively utilizes the advantages of 2D graphene oxide and 3D ZIF-8, which guarantees sufficient and reachable active sites; the 2D porous nanoarchitecture of Fe-N-C/NG promotes the ion diffusion and mechanical stability; both the FeNx atom clusters and N-doped graphene nanosheets facilitate the catalytic activity. This work introduces an innovative strategy to rationally design the nanoarchitecture and facilely synthesize nonprecious ORR catalysts with sufficient and uncovered active sites for high efficiency and durability.