Hexafluorophosphate additive enables durable seawater oxidation at ampere-level current density.
basic_science · Level V
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- Record sourced from PubMed, PMID 40442065.
- Also identified by DOI 10.1038/s41467-025-60413-0 and PMC identifier 12122868.
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Abstract
Direct seawater electrolysis at ampere-level current densities, powered by coastal/offshore renewables, is an attractive avenue for sustainable hydrogen production but is undermined by chloride-induced anode degradation. Here we demonstrate the use of hexafluorophosphate (PF₆⁻) as an electrolyte additive to overcome this limitation, achieving prolonged operation for over 5,000 hours at 1 A cm<sup>-2</sup> and 2300 hours at 2 A cm<sup>-2</sup> using NiFe layered double hydroxide (LDH) as anode. Together with the experimental findings, PF₆⁻ can intercalate into LDH interlayers and adsorb onto the electrode surface under an applied electric field, blocking Cl⁻ and stabilizing Fe to prevent segregation. The constant-potential molecular dynamics simulations further reveal the accumulation of high surface concentrations of PF<sub>6</sub><sup>-</sup> on the electrode surface that can effectively exclude Cl<sup>-</sup>, mitigating corrosion. Our work showcases synchronous interlayer and surface engineering by single non-oxygen anion species to enable Cl<sup>-</sup> rejection and marks a crucial step forward in seawater electrolysis.