Highly efficient and stable oxygen evolution from seawater enabled by a hierarchical NiMoSx microcolumn@NiFe-layered double hydroxide nanosheet array

Abstract

Developing efficient and robust oxygen evolution reaction (OER) catalysts in seawater is important for green hydrogen generation but remains a significant challenge. Herein, we report a hierarchical core–shell OER electrocatalyst consisting of NiFe-layered double hydroxide nanosheets uniformly coated on a NiMoS_x microcolumn supported on Ni foam (NiMoS_x@NiFe-LDH/NF). Such NiMoS_x@NiFe-LDH/NF shows excellent OER activity with a low overpotential of 297 mV to drive an industrial-level current density of 500 mA cm⁻² in alkaline seawater and can operate continuously for 500 h without apparent activity degradation. In situ Raman spectroscopy studies indicate that the high-valent molybdate ions can promote the generation of disordered NiOOH active species and protect catalysts from Cl⁻ corrosion during seawater oxidation. Additionally, the integrated alkaline seawater electrolyzer (with NiMoS_x/NF as the cathode) is demonstrated to reach a current density of 100 mA cm⁻² with a low voltage of 1.61 V, outperforming the benchmark Pt/C/NF||RuO₂/NF.