Dual-metal hydroxide heterojunction and chayote fruit biomass–derived hierarchical porous carbon for augmenting the performance of hybrid supercapacitors

Binary hydroxides-based pseudocapacitive nanoelectrodes and the delicate design of hierarchical heterostructures with novel physical and structural features can dramatically enhance the multiplicative properties. In this study, special binary hydroxide heterojunctions were developed by in-situ immobilizing yttrium/nickel (Y-Ni)–, samarium/nickel (Sm-Ni)–, or lanthanum/nickel (La-Ni) nanostructures on nickel foam (NF) current collector via a one-step hydrothermal approach for supercapacitors. The resulting Y-Ni, Sm-Ni, and La-Ni heterostructure nanoelectrodes reveal a high pseudocapacitive performance compared to the unitary Ni electrode because of the synergy effect. The Y, Sm, and La species can optimize the Ni(OH)2 at the surface and atomic levels, yielding robust Faradaic reactions and improved energy storage characteristics of supercapacitors. The formed heterojunctions enhance the electronic configurations and modulate the electron transport process. Besides, the hierarchical porous nanoframes expose more electrochemical active sites and maximize flexible electron/ion transport trajectories. As a positive electrode, the La-Ni hydroxide acquires a large specific capacitance (1395.8 F g−1 at 1 A g−1), remarkable rate capability (57.6 % capacitance retention with a 40-fold increase of the current density), and stable cycling activity (maintaining >79.3 % even after 5000 cycles). Furthermore, the asymmetric hybrid supercapacitor (AHSC) device employing the La-Ni positive electrode and phosphorus self-doped chayote fruit-derived hierarchical porous carbon (P-HPC) negative electrode delivers high energy and power densities (57.2 Wh kg−1 at 750 W kg−1). The established device yields good cycling performance, preserving 78.8 % of its initial capacitance after 12,000 charge-discharge cycles. Therefore, this work sheds substantial light on inspiring the development of cost-efficient nanomaterials by tuning the composition and electronic configuration for electrochemical supercapacitors.