Phosphorus-functionalized low-crystallinity transition-metal oxide nanorod arrays grown on carbon cloth for high-performance asymmetric supercapacitors

Abstract

Transition-metal oxides as the pseudocapacitive material have been increasingly investigated due to their high theoretical specific capacitance for supercapacitors (SCs). However, restricted to lack of active sites and poor conductivity, they usually display limited experimental capacitance, barely satisfying high energy density of SCs. Herein, we describe phosphorus functionalized low-crystallinity Co3O4 and Fe2O3 nanorod arrays on carbon cloth (Co3O4-P and Fe2O3-P), which can respectively behave as the flexible 3D cathode and anode for SCs. The formed phosphide on the surface of metal oxide provides the enhancement of electron transfer and the reduction of ions diffusion pathway. The optimized Co3O4-P 1.0 h cathode and Fe2O3-P 1.0 h anode deliver a high capacitance of 1180 and 477 mF cm−2, respectively. The asymmetric supercapacitor Co3O4-P//Fe2O3-P has been verified with an operating voltage of 1.5 V and stability over 5000 cycles and delivers an energy density of 73.6 μWh cm−2 at a power density of 0.38 mW cm−2. The phosphorus activation is expected to be widely applicable for the fabrication of porous and low-crystalline transition-metal oxide, thus opening up new avenues for energy storage.