Electrothermally Driven Nucleation Energy Control of Defective Carbon and Nickel-Cobalt Oxide-Based Electrodes

Abstract

Multielement metal/metal oxides/carbon-based support hybrids are promising candidates for high-performance electrodes. However, conventional solid-state synthesis utilizing slow heating-cooling rates is limited by discrepancies in their phase transition temperatures. Herein, we report a rational strategy to control the nucleation energy of defective carbon fibers (DCFs) and Ni-Co-oxide-based electrodes capable of electrochemical activation using electrothermal waves (ETWs). The ETWs, triggered by Joule heating passing through CFs and Ni-Co precursors, induce programmable high-temperature processes via adjustable input powers and durations. The first ETW (similar to 1500 degrees C) fabricates the presculpted DCFs, while the second ETW (similar to 600 degrees C) directly synthesizes NiCo2O4 spinel nanoparticles on the DCFs. Predesigning DCFs through the Gibbs free energy theory enables tunable control of nucleation energy and solution compatibility with Ni-Co precursors, allowing the morphological and compositional design of the optimal NiCo2O4@DCFs hybrids. Furthermore, they are electrochemically activated to change the morphologies and oxidation states of Ni-Co to more stable wrinkled structures strongly anchored to carbon supports and Ni-Co cations with low oxidation numbers. The activated NiCo2O4@DCFs electrodes exhibit outstanding specific capacitance and long-term cyclic stability (similar to 1925 F g(-1) and similar to 115-123% for 20 000 cycles). The ETWs offer a facile yet precise method to predesign carbon supports and subsequently synthesize hybrid electrodes.