Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
ACS Appl Mater Interfaces. 2022 May 18;14(19):22216-22224. doi: 10.1021/acsami.2c04764. Epub 2022 May 5.
The light-dependent reactions of photosynthesis use light energy to generate photoelectrons traveling through the thylakoid membranes (TMs). Extracting the photoelectrons from the TMs to form bioanodes can have various applications. Most studies focus on modifying the electrode materials to increase the collected photocurrent. Seldom studies have investigated how the orientation of the TMs influences photocurrent collection. In addition, the formation of reactive oxygen species (ROS) during photosynthesis is a challenge for stable photocurrent generation. Here, we enhanced the photoelectron transfer from the TMs to electrodes by depositing expanded thylakoids as planar supported membranes onto an electrode. The high contact area between the external electrodes and TMs per unit mass of thylakoid allows the thylakoid to more effectively transfer electrons to the electrodes, thereby reducing the free electrons available for the ROS generation. We expanded the naturally stacked thylakoids into liposomes through osmotic pressure and dropcasted them onto an Au electrode. The electrochemical impedance measurement showed that the supported membrane bioanode formed by the expanded liposomes had a lower photoelectron transfer resistance. Additionally, we observed that the expanded TM bioanode provided a higher photocurrent and was more durable to air/water interfacial tension. These results suggest that the effective contact between the expanded TM and electrodes can lead to more efficient electron transfer and increase the system robustness. The photo fuel cell (PFC) made by the expanded TM bioanode had a higher open-circuit voltage than the one made by the stacked TM bioanode. Interestingly, we found that PFCs made of high-load TM bioanodes had fast photocurrent decay under continuous operation at high cell voltages. The poor contact of large numbers of TMs with the electrodes at the high-load TM bioanodes could cause more ROS accumulation and therefore decreased the operational stability, supporting the importance of effective contact between TMs and the electrodes.
光合作用的光依赖反应利用光能产生穿过类囊体膜（TMs）的光电子。从 TMs 中提取光电子以形成生物阳极可以有各种应用。大多数研究都集中在修饰电极材料以增加收集的光电流。很少有研究调查 TMs 的取向如何影响光电流收集。此外，光合作用过程中活性氧物质（ROS）的形成是稳定光电流产生的一个挑战。在这里，我们通过将展开的类囊体沉积为平面支撑膜到电极上来增强 TMs 到电极的光电子转移。每个类囊体质量的外部电极和 TMs 之间的高接触面积允许类囊体更有效地将电子转移到电极，从而减少用于 ROS 生成的自由电子。我们通过渗透压将天然堆叠的类囊体扩展成脂质体，并将其滴铸到 Au 电极上。电化学阻抗测量表明，由展开的脂质体形成的支撑膜生物阳极具有更低的光电子转移电阻。此外，我们观察到扩展 TM 生物阳极提供了更高的光电流并且对空气/水界面张力更耐用。这些结果表明，扩展 TM 与电极之间的有效接触可以导致更有效的电子转移并提高系统的鲁棒性。由扩展 TM 生物阳极制成的光电燃料电池（PFC）具有比堆叠 TM 生物阳极制成的 PFC 更高的开路电压。有趣的是，我们发现，在高电池电压下连续运行时，高负载 TM 生物阳极制成的 PFC 具有更快的光电流衰减。高负载 TM 生物阳极中大量 TMs 与电极之间的不良接触可能导致更多的 ROS 积累，从而降低了操作稳定性，这支持了 TMs 和电极之间有效接触的重要性。
