Advanced hollow structure with functional Interface of NiCoP/NC achieved superior hydroxide ion storage for high-rate supercapacitor

Sluggish reaction kinetics and poor structure stability are the main problems that hinder the application of transition metal phosphides. Differing from the traditional single ligand strategy, a hollow spherical NiCoP with large-scale NiCoP//NC interfaces (DL-NiCoP/NC) was synthesized through co-assembling metal-organic frame-work (MOF) of 2-methylimidazole and 5-aminotetrazole double ligands. The experimental and theoretical calculation results show that the hollow structure with rich NiCoP//NC interfaces adjusts the local electronic environment, increases the adsorption energy of NiCoP for OH- and effectively optimizes the surface/solution pathway for OH- transfer, which contributes to capacitive-controlled and diffusion-controlled reaction. Based on the above research, the electrochemical reaction process and structural evolution of DL-NiCoP/NC electrode were elucidated. Benefits from the synergistic effects of hollow structure and interfacial interaction, DL-NiCoP/ NC electrode shows high specific capacitance (1551 F g-1 at 1 A g-1) and high-rate performance (78.1% capacitance retention at 30 A g-1). The assembled hybrid supercapacitor has favorable energy and power output (54.2 Wh kg-1 and 11,948.9 W kg-1), and excellent capacitance retention (83.7% after 8000 cycles). The fabricated pouch-type supercapacitor exhibited good application potential. This work provides a promising method to design structure with interface regulating for fast OH- storage materials.