Cobalt Phthalocyanine Modified Holey Graphene/Cobalt Phosphide as Advanced Electrodes with Boosted Ion/Charge Transfer in Capacitive Storage

Abstract

Transition metal-based electrodes are appealing for energy storage, but suffering from the sluggish ion diffusion and charge transfer dynamics. Herein, holey graphene (HG) with high conductivity and ample pores is firstly employed as the scaffold to grow cobalt phosphide (CoP), and cobalt phthalocyanine (CoPc) molecules are used to modify the HG by strong π-π interactions to inhibit the layer stacking of HG and facilitate the ion/charge transfer. HG can provide sufficient ion/charge transfer channels during charge/discharge processes. In addition, the CoPc modification on HG can not only hamper their self-aggregation, but also optimize the charge distribution and boost the charge transfer. The density functional theory calculation indicates that the CoP/HG/CoPc has strong ion adsorption and rapid charge transport. Benefiting from the improved ion diffusion and charge transfer characteristics, the as-constructed CoP/HG/CoPc heterostructures exhibit a specific capacitance of 970.8 F g-1 at 1 A g-1. Moreover, the as assembled asymmetric supercapacitors deliver an energy density of 47.1 Wh kg-1 at a power density of 726.4 W kg-1, and 87.7% capacitance retention after 10,000 cycles. Both experiments and calculations unveil the capacitive enhancement mechanism of the CoP/HG/CoPc heterostructures, providing new thoughts on the design of advanced supercapacitor electrodes.

Keywords: cobalt phosphide, holey graphene, cobalt phthalocyanine, ion/charge transfer, supercapacitors