Construction of Heterojunction‐Rich Metal Nitrides Porous Nanosheets Electrocatalyst for Alkaline Water/Seawater Splitting at Large Current Density

The exploiting electrocatalysts for water/seawater electrolysis with remarkable activity and outstanding durability at industrial grade current density remains a huge challenge. Herein, CoMoN_x and Fe-doped CoMoN_x nanosheet arrays are in-situ grown on Ni foam, which possess plentiful holes, multilevel heterostructure, and lavish Co_5.47N/MoN@NF and Fe-Co_5.47N/MoN@NF interfaces. They require low overpotentials of 213 and 296 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline media to achieve current density of 800 mA cm^-2, respectively, and both possess low Tafel slopes (51.1 and 49.1 mV dec^-1) and undiminished stability over 80 h. Moreover, the coupled Co_5.47N/MoN@NF and Fe-Co_5.47N/MoN@NF electrolyzer requires low voltages of 1.735 V to yield 500 mA cm^-2 in alkaline water. Notably, they also exhibit exceptional electrocatalytic properties in alkaline seawater (1.833 V@500 mA cm^-2). The experimental studies and theoretical calculations verify that Fe doping does reduce the energy barrier from OH* to O* intermediates during OER process after catalyst reconstruction, and the non-metallic N site from MoN exhibits the lowest theoretical overpotential. The splendid catalytic performance is attributed to the optimized local electron configuration and porous structure. This discovery provides a new design method toward low-cost and excellent catalysts for water/seawater splitting to produce hydrogen.