Multifunctional material integrated from walnut shell-derived porous carbon and Co/Zn-S for high-performance supercapacitors and adsorbents

Abstract

The development of materials that can be applied to high-energy-density supercapacitors and high-efficiency adsorbents remains challenging. In this paper, a novel walnut shell-derived porous carbon (WSC) decorated bimetallic sulfide (Co/Zn-S@WSC) composite was successfully fabricated by a facile high-temperature alkaline activation and vulcanization strategy. The WSC with a three-dimensional (3D) porous structure plays the role of a “skeleton” during the preparation and growth of the composite, allowing the metal-organic framework (MOF) derived sulfides Co/Zn-S to be distributed evenly across the 3D framework of porous carbon. The prepared Co/Zn-S@WSC demonstrates a multi-level pore structure, which reduces ion transport paths and facilitates energy storage, thus the electrochemical properties of the electrode are enhanced efficiently. The electrode samples were tested in a 6 mol/L KOH electrolyte. Co/Zn-S@WSC presents a specific capacitance of 987.2 F·g−1 at a current density of 1 A·g−1. In addition, an asymmetric supercapacitor (ASC), using Co/Zn-S@WSC (positive electrode) and WSC (negative electrode), shows a high energy density of 42.59 Wh·kg−1 at a power density of 374.88 W·kg−1 and cycling stability with 92% capacity retention after 10,000 cycles. Benefiting from a rational hierarchical pore structure, Co/Zn-S@WSC exhibits the promising adsorption capibilities for methylene blue (MB). A simple, efficient, and practical method for the development and application of novel multifunctional materials is provided by this work.