Ultrathin Mesoporous NiCo₂O₄ Nanosheets Supported on Ni Foam as Advanced Electrodes for Supercapacitors

Abstract A facile two‐step method is developed for large‐scale growth of ultrathin mesoporous nickel cobaltite (NiCo 2 O 4 ) nanosheets on conductive nickel foam with robust adhesion as a high‐performance electrode for electrochemical capacitors. The synthesis involves the co‐electrodeposition of a bimetallic (Ni, Co) hydroxide precursor on a Ni foam support and subsequent thermal transformation to spinel mesoporous NiCo 2 O 4 . The as‐prepared ultrathin NiCo 2 O 4 nanosheets with the thickness of a few nanometers possess many interparticle mesopores with a size range from 2 to 5 nm. The nickel foam supported ultrathin mesoporous NiCo 2 O 4 nanosheets promise fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with an ultrahigh specific capacitance of 1450 F g −1 , even at a very high current density of 20 A g −1 , and excellent cycling performance at high rates, suggesting its promising application as an efficient electrode for electrochemical capacitors.