Ultrahigh‐Performance Pseudocapacitor Electrodes Based on Transition Metal Phosphide Nanosheets Array via Phosphorization: A General and Effective Approach

In this study, a general and effective phosphorization strategy is successfully demonstrated to enhance supercapacitor performance of various transition metals oxide or hydroxide, such as Ni(OH) 2 , Co(OH) 2 , MnO 2 , and Fe 2 O 3 . For example, a 3D networked Ni 2 P nanosheets array via a facile phosphorization reaction of Ni(OH) 2 nanosheets is grown on the surface of a Ni foam. The Ni foam‐supported Ni 2 P nanosheet (Ni 2 P NS/NF) electrode shows a remarkable specific capacitance of 2141 F g −1 at a scan rate of 50 mV s −1 and remains as high as 1109 F g −1 even at the current density of 83.3 A g −1 . The specific capacitance is much larger than those of Ni(OH) 2 NS/NF (747 F g −1 at 50 mV s −1 ). Furthermore, the electrode retains a high specific capacitance of 1437 F g −1 even after 5000 cycles at a current density of 10 A g −1 , in sharp contrast with only 403 F g −1 of Ni(OH) 2 NS/NF at the same current density. The similar enhanced performance is observed for Ni 2 P powder, which eliminates the influence of nickel foam. The enhanced supercapacitor performances are attributed to the 3D porous nanosheets network, enhanced conductivity, and two active components of Ni 2+ and P δ− with rich valences of Ni 2 P.