Iron phthalocyanine decorated porous biomass-derived carbon as highly effective electrocatalyst for oxygen reduction reaction

Searching for a low-cost, high-activity and stable nonprecious metal electrocatalyst for the oxygen reduction reaction (ORR) is critical to the application of energy conversion devices, such as zinc-air batteries and proton exchange membrane fuel cells. Herein, renewable and inexpensive black locust leaves were used as carbon and nitrogen precursors to prepare porous biomass-derived carbon (PBC) using K2FeO4 as the activator and then decorated by iron phthalocyanine (FePc) with a free-pyrolysis process to obtain the electrocatalyst FePcx/PBC. Notably, the as-obtained PBC possesses a large specific surface area and hierarchically porous structure, facilitating the exposure of active sites and diffusion of O2 as well as the electrolytes during the ORR process. Compared with commercial Pt/C, the half-wave potential (E1/2 =0.91 V) and limiting current density (JL=5.03 mA·cm−2) of FePc0.5/PBC positively shifted nearly 70 mV and increased 0.44 mA·cm−2, respectively, and an obvious enhancement in stability and tolerance to methanol can be observed. Moreover, the assembled zinc-air battery using FePc0.5/PBC as the air-cathode catalyst exhibits an open-circuit voltage of 1.452 V and a specific capacity of 812.1 mAh·g−1, much higher than those of Pt/C (1.435 V, 749.4 mAh·g−1). This work develops a feasible, convenient and economic strategy to fabricate effective Pt-free ORR electrocatalysts for relevant energy conversion devices.