Comparison of electrochemical response and electric field emission characteristics of pristine La2NiO4 and La2NiO4/CNT composites: Origin of multi-functionality with theoretical penetration by density functional theory

Electrochemical performances of as-prepared La2NiO4 and La2NiO4@CNT based electrode are investigated in a 1M KOH solution using a three-electrode configuration. The La2NiO4 electrode delivers the specific capacity (C-sp) 284 mAh g(-1) at a current density 1.5 A g(-1) with rate capability 74.5% at a current density 12 A g(-1) and its value intensified up to 426 mAh g(-1) with capability 82.1% at identical current density due to incorporation of CNT. Long-range stability and Nyquist plot (Z'v s.Z '') of the La2NiO4@CNT electrode exhibit better cyclic performances with capacity retentivity 93% after 30 00 cycles and excellent charge transfer characteristics than pristine La2NiO4 electrode (capacity retentivity 85.6%). Fowler-Nordheim tunneling in electric field emission of CNT modified La2NiO4 exhibits superior current density (J similar to 1705 mu A/cm(2)) with inferior turn-on@1 mu A/cm(2) and threshold field@10 mu A/cm(2) 1.92 V/mu m and 2.15 V/mu m respectively. The enhanced electronic states near Fermi level for hybrid La2NiO4/CNT leading to improved conducitivity, increase mobility of electrolytic ions in the open space of CNTs and higher quantum capacitance support the improved charge storage performance. There is charge transfer from La2NiO4 to CNT due to interaction between d orbitals of Ni and La with 2p orbital of C. Also, reduction in work function for hybrid La2NiO4/CNT compared to pristine La2NiO4, introduction of defects near the boundary and improved conductivity attribute towards higher emission current observed in the experiment. (C) 2020 Elsevier Ltd. All rights reserved.