Boosted electrochemical properties from the surface engineering of ultrathin interlaced Ni(OH)2 nanosheets with Co(OH)2 quantum dot modification

Abstract

Nanoscale surface engineering of electroactive architectures is of paramount importance in high-performance supercapacitor applications based on surface-controlled charge storage mechanisms. Herein, we exploit Co(OH)₂ quantum dots (CoQDs) as a surface modifier and report a simple and effective strategy for anchoring CoQDs on ultrathin interlaced Ni(OH)₂ nanosheets. Impressively, the 2D/0D heterostructure of CoQD-interspersed Ni(OH)₂ nanosheets (Ni(OH)₂-CoQD) exhibits greatly enhanced capacitive behavior compared with pristine Ni(OH)₂ nanosheets, exhibiting a higher capacitance (3244 F g⁻¹vs. 2124 F g⁻¹ at 5 mA cm⁻²), superior rate capability and better cycling stability. Density functional theory (DFT) calculations reveal the accumulation of additional electrons and reduced adsorption energy of OH⁻ at the Ni(OH)₂-CoQD interphase, which are the primary reasons for the enhanced electrochemical performance. An asymmetric full cell with Ni(OH)₂-CoQD as the positive electrode has been fabricated, achieving a maximum energy density of 46 W h kg⁻¹ at 141 W kg⁻¹, and excellent cycling stability, where 84.1% of the initial capacitance is retained over 5000 cycles. This work brings a new opportunity to pseudoactive electrode material design by employing semiconductive quantum dots for surface modification.