Efficient alkaline seawater oxidation by a three-dimensional core-shell dendritic NiCo@NiFe layered double hydroxide electrode

Abstract

Seawater electrolysis for hydrogen generation has received increasing attention recently due to the scarcity of freshwater and the additional prospect of seawater desalination. The development of non-noble-metal-based oxygen evolution reaction (OER) electrocatalysts with high catalytic activity, long-term durability, and high OER selectivity is crucial for large-scale seawater electrolysis but remains a significant challenge. Here we develop a three-dimensional core-shell dendritic catalyst by vertically growing NiFe layered double hydroxide (LDH) nanosheets on dendritic NiCo branches (denoted as NiCo@NiFe LDH). The dendritic NiCo@NiFe LDH is highly active and stable in alkaline seawater due to its large surface area, fast charge transfer and effective mass transfer, and excellent corrosion resistance. It requires only a small overpotential of 222 mV to achieve current densities of 100 mA cm−2 in 1 M KOH seawater. To deliver a large current density of 500 mA cm−2, the NiCo@NiFe LDH catalyst requires a record-low overpotential of 266 mV. The nearly 100% OER Faradaic efficiency and the absence of ClO− in the electrolyte following seawater electrolysis indicate the high OER selectivity of our catalyst. The stability of NiCo@NiFe LDH in seawater is proven by its small overpotential fluctuation at a constant current density of 500 mA cm−2 over 100 h.