▎ 摘　　要

The direct hydrazine fuel cell (DHFC) emerges as a promising tool to produce electricity without any carbon emission. The electrocatalyst plays a role central to the performance of the DHFC. Thus, development of cost-effective bifunctional electrocatalysts remains a key to make this technology practically viable. Herein, we report a single-step hydrothermal synthesis route to couple MnFe2O4 nanoparticles (NPs) with nitrogen-doped reduced graphene oxide (h-MnFe2O4 NPs/N-rGO) and demonstrate its bifunctional role as an electrocatalyst for both anodic hydrazine electrooxidation and cathodic reduction of molecular oxygen. The as-synthesized h-MnFe2O4 NPs/N-rGO composite not only catalyzes hydrazine electrooxidation via a quasi-4-electron pathway (n = 3.94) with a small Tafel slope (106 mV decade(-1)) but is also capable of reducing molecular oxygen through an efficient 4-electron pathway. The oxygen reduction performance of the present composite is found to be comparable to that of the state-of-the-art Pt/C catalyst. In addition, the bifunctional electrocatalytic behavior of the h-MnFe2O4 NPs/N-rGO composite is found to be superior to those of MnFe2O4 NPs/rGO, pristine MnFe2O4 NPs, N-rGO alone, and the physical mixture of MnFe2O4 NPs and N-rGO. The improved electrocatalytic efficiency of the h-MnFe2O4 NPs/N-rGO composite originates from the synergetic physicochemical properties of MnFe2O4 NPs and N-rGO, which facilitates analyte diffusion, reduces charge transfer resistance, and offers a greater number of active sites for the catalytic reactions.