Coupling Co2P nanoparticles onto N,P-doped biomass-derived carbon as efficient electrocatalysts for flexible Zn-air batteries

Catalysts for oxygen conversion play an important role in energy storage and conversion technologies such as metal-air batteries. Developing highly active, stable, and low-cost catalysts is critical for further implementation of the above technologies. Herein, an efficient oxygen electrocatalyst with Co2P nanoparticles (NPs) coupling onto N,P-doped porous carbon nanosheets (Co2P@NPAC) derived from cotton stalk is successfully designed and prepared via activation, hydrothermal treatment, and pyrolysis procedure. The excellent properties of electrical conductivity, mass transfer, and synergistic integration between Co2P and N,P-doped carbon endow Co2P@NPAC composite with superior oxygen reduction reaction/oxygen evolution reaction (ORR/OER) performance. Co2P@NPAC catalyst achieves ORR activity with half-wave potential of 0.85 V and high OER activity with overpotential of 261 mV at 10 mA<middle dot>cm(-2). The flexible Zn-air batteries (ZABs) based on Co2P@NPAC catalyst reveal outstanding performances with a high open-circuit voltage (1.38 V), a peak power density of (75 mW<middle dot>cm(-2)), and a low charge-discharge voltage gap (0.74 V, similar to 200 cycles). The flexible ZABs express the stable discharge-charge voltage gap at various bending states. This work provides interesting inspiration for the ingenious design of efficient carbon electrocatalysts from biomass with potential application of energy storage and conversion devices.