Conventional water-splitting electrolysis drives the H₂ and O₂ evolution reactions (HER and OER, respectively) simultaneously with large voltage inputs. Herein, two inexpensive iron complexes as proton-independent electron reservoirs (ERs) are described for decoupled water electrolysis. (Ferrocenylmethyl)trimethylammonium chloride and Na₄[Fe(CN)₆], which have proper redox potentials in aqueous media, are able to couple their oxidation with HER. The subsequent reduction of the oxidized ER⁺ is then paired with OER. Both steps require much smaller voltage than that of direct water splitting. Nearly 100% Faradic efficiency and remarkable cycling stability were obtained for both ERs. Such decoupled water splitting could also be driven by photovoltaic cells with small photovoltages under sunlight irradiation. Furthermore, a two-step electrolysis of HER and the oxidation of 5-hydroxymethylfurfural mediated by Na₄[Fe(CN)₆] was demonstrated under alkaline conditions, producing H₂ and 2,5-furandicarboxylic acid. This work presents a decoupled water electrolyzer design with great flexibility and safety advantages.

常规的水分解电解法在大电压输入下同时驱动H ₂和O ₂析出反应（分别为HER和OER）。在本文中，描述了两种廉价的铁络合物，作为与质子无关的电子储库（ER），用于去离子水电解。在水性介质中具有适当氧化还原电位的（二茂铁基甲基）三甲基氯化铵和Na ₄ [Fe（CN）₆ ]能够将其氧化与HER偶联。氧化后的ER ^+的还原然后与OER配对。这两个步骤所需的电压都比直接水分解的电压小得多。两种ER均获得了近100％的法拉第效率和出色的循环稳定性。这种解耦的水分解还可以由在阳光照射下具有小的光电压的光伏电池驱动。此外，在碱性条件下，证明了由Na ₄ [Fe（CN）₆ ]介导的HER的两步电解和5-羟甲基糠醛的氧化，生成H ₂和2,5-呋喃二甲酸。这项工作提出了一种具有高度灵活性和安全性优势的去耦水电解器设计。