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, CoMoNx and Fe-doped CoMoNx nanosheet arrays are in-situ grown on Ni foam, which possess plentiful holes, multilevel heterostructure, and lavish Co5.47N/MoN@NF and Fe-Co5.47N/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 Co5.47N/MoN@NF and Fe-Co5.47N/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. The electrode pairs of Co5.47N/MoN@NF and Fe-Co5.47N/MoN@NF for electrolysis of water/seawater are synthesized by the hydrothermal and calcination methods. The experimental results and theoretical investigation show that thanks to the porous structure, synergistic effect, excellent conductivity, and large specific surface area, the electrode pairs exhibits remarkable activity in alkaline electrolysis of water/seawater at large current density. image