Closely packed planar polyphthalocyanine iron/hierarchical three-dimensional graphene as an oxygen electrocatalyst for the ORR and OER, and zinc-air batteries

The development of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts with high performance and excellent stability is meaningful for fuel cells. Herein, two-dimensional closely packed amide polyphthalocyanine iron (CPMPcFe) supported on hierarchical three-dimensional graphene (3D-HG) has been well prepared. CPMPcFe/3D-HG possessed a micro-mesoporous graphene structure where CPMPcFe was uniformly distributed in the inner and surface of the 3D-HG. Owing to the pi bonds of both CPMPcFe and 3D-HG, there is a powerful pi-pi bond interaction between CPMPcFe and 3D-HG, which increases the electron cloud density, and it could be beneficial for improving the catalytic activity and durability. Electrochemically, CPMPcFe/3D-HG exhibits an excellent half-wave potential of 0.88 V (vs. RHE), and the electron transfer number of CPMPcFe/3D-HG is 3.99 @ 0.6 V (vs. RHE). The small value of overvoltage further indicates the excellent bifunctional catalytic performance. Additionally, a home-built Zn-air battery with CPMPcFe/3D-HG as the cathode exhibits a high power density of 193 mW cm(-2), a specific capacity of 683 mA h g(-1), and remarkable long-term stability. These results indicated that CPMPcFe/3D-HG could be a promising electrocatalyst for metal-air batteries.