Fe-NiO/MoO2 and In-situ reconstructed Fe, Mo-NiOOH with enhanced negatively charges of oxygen atoms on the surface for salinity tolerance seawater splitting

Abstract

Seawater electrolysis is a promising technique for H2 production on a large scale. However, the electrocatalytic activity and stability will be deteriorated as the increase of salt concentrations which happened in the seawater splitting. Herein, through the electrodeposition and rapid Joule heating method, the Fe-NiO/MoO2 heterostructure is designed as a highly active bifunctional electrocatalyst. During the OER possess, Fe-NiO/MoO2 is reconstructed to the Fe, Mo-NiOOH with Fe and Mo co-doping. Based on the theoretical analysis, more electrons were transferred to the O atoms on the surface of Fe, Mo-NiOOH, thereby forming a more negatively charged surface. Moreover, that surface is found to repel Cl− ions while enriching H2O molecules to form a thin water layer on Fe, Mo-NiOOH surface based on molecule dynamics (MD) simulation, thereby improving the anti-corrosion capacity of Fe, Mo-NiOOH. The reconstructed Fe, Mo-NiOOH achieved an overpotential of 399mV at 1000mA·cm−2 in alkaline seawater, and the increase of overpotential for Fe, Mo-NiOOH was about 0.02V at 500mAcm−2 from 0M to 3M NaCl in 1M KOH electrolyte. For the HER, Fe-NiO/MoO2 achieved an overpotential of 169mV and 417mV at 100 and 1000mA·cm−2 in alkaline seawater, respectively, and the increase of overpotential for Fe-NiO/MoO2 was about 0mV at 500mAcm−2 from 0M to 3M NaCl in 1M KOH electrolyte. This work sheds fresh light into the development of efficient electrocatalysts for salinity tolerance seawater splitting.