With suitable water dissociation (WD) catalysts, bipolar membranes (BPMs) can efficiently dissociate water into H⁺ and OH^– at the junction between anion- and cation-exchange layers (AEL and CEL, respectively). First, however, water must be transported through the AEL or CEL and thus against the outward flow of hydrated H⁺ and OH^–. This is a challenge intrinsic to the BPM architecture and limits operation to current densities typically less than ∼0.5 A·cm^–2. Here we explore how water transport affects durability and performance in reference alkaline and acidic membrane electrolyzers, and we use the insight gained to design BPMs with improved water transport. We demonstrate a thin-CEL BPM (2-μm Nafion CEL|∼200 nm TiO₂|∼200 nm NiO + ionomer|50 μm Sustainion AEL) which maintains a pH difference of ∼14 units between the anode and cathode for current densities of up to 3.4 A·cm^–2 with a total water electrolysis voltage of ∼4 V and an estimated WD overpotential of ∼1.5 V. Such high-current-density operation is crucial for key emerging BPM applications, including in water and carbon-dioxide electrolyzers and in (regenerative) fuel cells.

中文翻译：

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薄的阳离子交换层可通过改善水的输送来实现高电流密度双极膜电解槽

与合适的水的解离（WD）的催化剂，双极性膜（BPM的）可以有效离解成水ħ ⁺和OH ^-在之间阴离子和阳离子交换层（分别为AEL和CEL）的交界处。然而，首先，水必须通过AEL或CEL输送，从而抵靠向外流动水合H的⁺和OH ^- 。这是BPM体系结构固有的挑战，并将操作限制在电流密度通常小于〜0.5 A·cm ^{–2的情况下}。在这里，我们探讨了水输送如何影响参考碱性和酸性膜电解槽的耐用性和性能，并且我们利用获得的见识来设计具有改善的水输送性能的BPM。我们展示了一种薄CEL BPM（2-μmNafion CEL |〜200 nm TiO ₂ |〜200 nm NiO +离聚物| 50μmSustainion AEL），在电流密度为2的条件下，其阳极和阴极之间的pH差保持在约14个单位。高达3.4 A·cm ^–2的水电解总电压约为4 V，WD过电位估计约为1.5V。这种高电流密度操作对于关键的新兴BPM应用至关重要，包括在水和二氧化碳中的应用电解槽和（再生）燃料电池。