Surface boron modification of an anthraquinone‐2‐sulfonate‐intercalated NiFe layered double hydroxide film for durable anodic operation in chloride‐containing alkaline electrolyte

A mild NaBH 4 treatment of an anthraquinone‐2‐sulfonate (AQS)‐intercalated Ni 2 Fe 1 layered double hydroxide film, grown binder‐free on Ni foil, condenses boron onto the hydroxide sheets as BOMO linkages with a B 1 s binding energy of 191.6 eV, and partially releases the organic gallery so that the residual AQS lies flat. The metal composition is unchanged, with an Fe/Ni ratio of 0.66 before and 0.64 after treatment. Under galvanostatic anodic operation at 200 mA cm −2 in 1 M KOH containing 0.5 M NaCl the treated film sustains the current for about 87 h against about 13 h for the untreated film and retains a coherent surface where the untreated film fragments and sheds solid into the cell. Raman spectroscopy collected within 10 min of halting polarization accounts for the difference. Boron redshifts the as‐made metal–oxygen modes, the signature of electron withdrawal by the Lewis‐acidic BO network at the surface. Both films reconstruct to γ‐NiOOH on activation, but only the boron‐modified film retains that band, stable at 552–554 cm −1 to about 72 h, whereas the untreated film loses it from about 6 h as its metal–oxygen bonding softens. The window of γ‐NiOOH stability tracks the operating lifetime in both films, identifying retained surface boron as the factor that preserves the active surface in chloride‐containing alkali.