Surface-Active Edge-Rich sites in 2D layered cobalt Hydroxide/Phosphide interfaces for High-Performance aqueous Sodium-Ion energy storage

Abstract

Enhanced edge-rich electroactive sites are a promising approach for 2D interface design in storage materials, allowing control over structural attributes of surface active-sites, thereby improving electrochemical features. This research explores the surface modification of edge-rich cobalt hydroxide/phosphide (CHP) in a 2D/2D layered structure, achieved via a dual-stage electrodeposition method for aqueous sodium-ion energy storage systems. The CHP-15 electrode exhibited superior pseudocapacitive behavior, with a remarkable areal capacitance of 463 mF cm−2, attributed to increased surface electroactive sites resulting from controlled 2D/2D hydroxide/phosphide layered formation. The CHP architecture, featuring the synergistic effects of 2D hexagonal layered Co(OH)2 with a 2D CoP3 layered framework, confirmed its excellent performance in Na-ion adsorption calculations through DFT analysis. Furthermore, asymmetric Na-ion supercapacitors (ANISCs) were assembled using CHP-15 electrode (positive electrode) and an activated carbon electrode (negative electrode), operating within wide potential window of 2 V. The ANISCs demonstrated an excellent energy storage capability, with maximum specific energy of 52.89 W h kg−1 and specific power of 12449 W kg−1. To evaluate real-time functionality, ANISCs were assembled into coin cells and demonstrated their capabilities by powering 27 LEDs, including green, blue, and white. The results provide significant insights into the benefits of surface engineering in cobalt hydroxide-based interface materials, contributing to advancements in sustainable Na-ion energy storage.