Stable seawater oxidation at high-salinity conditions promoted by low iron-doped non-noble-metal electrocatalysts

Abstract

Electrocatalytic seawater splitting offers a promising avenue for cost-effective and environmentally friendly hydrogen production. However, the activity of catalysts has significantly degraded at high-salinity conditions, preventing commercial-scale practical applications. Here, we demonstrate that iron-doped nickel-based electrocatalysts with low doping concentration exhibit an outstanding performance for the oxygen evolution reaction (OER) in seawater, particularly at high-salinity conditions. Notably, the OER catalysts present only a marginal increase in overpotential of ∼5 mV as the sodium chloride concentration in the electrolyte increases from 0 M to saturation. Furthermore, the low iron-doped electrocatalysts sustain consistent oxygen generation over 100 h of operation in a saturated seawater electrolyte. Supported by first-principles calculations, we unravel that low-concentration iron doping in Ni-based catalysts can mitigate chloride ion adsorption, thereby amplifying the OER activity in saturated seawater electrolytes, which is in contrast with high iron-doped electrocatalysts. Our work provides a useful perspective on designing catalysts for electrolytic seawater OER, potentially paving the way for large-scale implementation of seawater splitting technologies.