Tailoring activation of CoNiO nanoparticles/porous carbon nanofibers by atomic doping for high performance supercapacitors.

Metal-organic framework (MOF) materials are rich in active sites and have a high specific surface area, which make them potential electrode materials. In this work, a simple immersion method combined with a carbonization treatment process is applied to prepare MOF derived composite materials (CoNiO/PCNFs). Among them, cobalt-based MOFs (Co-MOFs) are selected as the precursor and doped with Ni atoms, and the ratio of Co and Ni is tailored to acquire a high-performance electrode. The electrochemical results show that when the ratio of Co to Ni is 2 : 2, the prepared CoNiO/PCNFs-2 electrode has high capacitance (912.4 F g-1 at 1 A g-1) and superior rate capability (retention is above 50% at 100 A g-1). Additionally, it is highly stable at 20 A g-1 (nearly no degradation after 6000 cycles). Density Functional Theory (DFT) calculations indicate that the Ni doping models present lower formation energy and better -OH group adsorption properties. Moreover, the density of electronic state (DOS) and differential charge density distribution demonstrate that Ni doping effectively enhances the charge transport during the charging and discharging processes, which is beneficial to enhance the energy storage of the electrode materials. In conclusion, this work presents a strategy to design MOF-derived composite electrodes. The experimental tests and theoretical calculations explore the energy storage process and prove that the CoNiO/PCNF electrode materials have great potential for applications.