2 butanol

Tetraethylorthosilicate (TEOS; 98%; Sinopharm Chemical Reagent Co., Ltd.), TPAOH (25% aqueous solution, Macklin), 2-butanol (C₄H₁₀O, 99%; Macklin), potassium chloride (KCl, 99.8%; Macklin), hexaammineruthenium(III) chloride ([Ru(NH₃)₆]Cl₃, 99%, Strem), and sodium chloride (NaCl, 99.5%; Macklin) were used without any further purification. [Fe(phen)₃]Cl₂ was synthesized in our laboratory, according to the well-documented procedure. Briefly, 0.994 g of iron(II) chloride tetrahydrate (FeCl₂·4H₂O, 99.95%; Macklin) was dissolved in 250 ml of deionized (DI) water. Consequently, 2.97 g of 1,10-phenanthroline monohydrate (C₁₂H₈N₂·H₂O, 98%; Macklin) was added into this aqueous solution. After vigorous stirring for 3 hours, [Fe(phen)₃]Cl₂ solution (20 mM) was prepared and stored in the dark before use. Glass plates (2 cm × 2 cm) were immerged in piranha solution (H₂SO₄/H₂O₂ = 2/1 v/v) and heated at 90°C for 1 hour, then washed with copious DI water, and stored in DI water before seed layer deposition. γ-Al₂O₃ discs (Fraunhofer IKTS, Germany) were pretreated with ∼6% hydrochloric acid and extensively washed with water afterward. Pt electrodes (Shanghai Yueci Electronic Technology Co., Ltd) and Al plates were polished with sandpapers, thoroughly washed with ethanol, and stored in DI water before deposition.