Phosphate Ion Functionalized Co₃O₄ Ultrathin Nanosheets with Greatly Improved Surface Reactivity for High Performance Pseudocapacitors

A surface-modified Co₃ O₄ ultrathin nanosheet (denoted as PCO) is reported via controllable phosphate ion functionalization for pseudocapacitors. An energy density of 71.6 W h kg⁻¹ (at 1500 W kg⁻¹ ) is achieved by the PCO-based pseudocapacitor. The unique porous nanosheet morphology, high surface reactivity, and fast electrode kinetics of PCO are found to be responsible for the enhanced pseudocapacitive performance.