氫氧分離式光電分解水

摘要：

太陽能產氫一直是人類孜孜追求的目標。但如何實現大規模持續、廉價產氫是為棘手又亟待解決的問題。在傳統電解槽結構中，產氫和產氧在同一槽中。但這一方式在光電產氫領域受到了大的限制。如何整合太陽能的轉化與電解水產氫成為關鍵。本文中，作者通過分離產氫、產氧過程，并利用輔助電作為“調節劑”，成功實現大面積太陽能轉化與集中式產氫，太陽能產氫轉換效率達到7.5 %。同時，較之傳統光電化學體系，該方法在成本、安全性以及穩定性上都具有一定的競爭優勢。

先來看看作者的構想圖：

好和諧的一張圖。地毯式的太陽能面板加集中式電解水產氫。

Conceptual illustration of a solar hydrogen refuelling station with distributed PEC solar cells producing O2 and a centralized H2 generator.A detailed conceptual design of the solar field is illustrated in Supplementary Fig. 26.

傳統電解水裝置如下圖1a、1b所示，產氫、產氧在同一裝置中進行，利用離子交換膜或者鹽橋實現連接。近期，人們提出了一種新型聚合物薄膜電解槽結構。其利用可溶性分子氧化還原調節劑（硅鎢酸）實現產氫和產氧的分離，如下圖1c所示。但其效率低下，且需要貴金屬鉑作為產氫催化劑。本文則采用固體氧化還原調節劑作為離子交換體系，實現氫氧分離，并可多次循環利用。至于材料的選擇方法請參見原文。

圖 1

Figure 1 | Water electrolysis cell architectures. a, Conventional configuration of an alkaline water electrolysis cell. b, The same as in a with the membrane replaced by a salt bridge. c, The new PEM electrolyser configuration proposed in ref. 6 with a soluble redox mediator that enables decoupling the H2 and O2generation steps. d, Our membrane-free configuration for alkaline water electrolysis in separate hydrogen and oxygen cells8. The anode can be replaced by a photoanode or a photoanode–photovoltaic tandem stack, thus turning the electrolysis cell into a PEC water splitting solar cell that directly convert water and solar power to hydrogen fuel.

具體表征數據見下圖2、3和表一：

圖 2

Figure 2 | Two-cell water electrolysis cycles in separate hydrogen and oxygen cells. a, Vappl as a function of time during 20 h of operation at a constant current of 45 mA (5 mA cm−2 ). b, The cycle duration plotted against the cycle number. The measurement was carried out in 1 M NaOH alkaline aqueous solution at ambient temperature.

圖 3

Figure 3 | Solar water splitting system with separate oxygen and hydrogen cells. Current density–voltage (J–V) characteristics of the individual components, the PV module (red curve) and water electrolysis system (blue curve), and the operation points of the coupled PV–electrolysis system (green dots). The red X marks the maximum power point of the PV module. The black dashed line curve shows the J–V characteristics of a PV module of the same model based on the vendor’s specifications. The inset shows a schematic illustration of the system.

表一

水平有限，更多準確信息請移步原文。