Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Umultowska 85, 61-614, Poznan, Poland.
School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
Photosynth Res. 2018 Oct;138(1):103-114. doi: 10.1007/s11120-018-0550-8. Epub 2018 Jul 3.
As one of a number of new technologies for the harnessing of solar energy, there is interest in the development of photoelectrochemical cells based on reaction centres (RCs) from photosynthetic organisms such as the bacterium Rhodobacter (Rba.) sphaeroides. The cell architecture explored in this report is similar to that of a dye-sensitized solar cell but with delivery of electrons to a mesoporous layer of TiO by natural pigment-protein complexes rather than an artificial dye. Rba. sphaeroides RCs were bound to the deposited TiO via an engineered extramembrane peptide tag. Using TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) as an electrolyte, these biohybrid photoactive electrodes produced an output that was the net product of cathodic and anodic photocurrents. To explain the observed photocurrents, a kinetic model is proposed that includes (1) an anodic current attributed to injection of electrons from the triplet state of the RC primary electron donor (P) to the TiO conduction band, (2) a cathodic current attributed to reduction of the photooxidized RC primary electron donor (P) by surface states of the TiO and (3) transient cathodic and anodic current spikes due to oxidation/reduction of TMPD/TMPD at the conductive glass (FTO) substrate. This model explains the origin of the photocurrent spikes that appear in this system after turning illumination on or off, the reason for the appearance of net positive or negative stable photocurrents depending on experimental conditions, and the overall efficiency of the constructed cell. The model may be a used as a guide for improvement of the photocurrent efficiency of the presented system as well as, after appropriate adjustments, other biohybrid photoelectrodes.
作为利用太阳能的新技术之一，人们对基于光合生物（如球形红杆菌（Rba.））反应中心（RCs）开发光电化学电池产生了兴趣。本报告中探索的电池结构类似于染料敏化太阳能电池，但通过天然色素蛋白复合物而不是人工染料将电子输送到介孔 TiO 层。Rba. sphaeroides RCs 通过工程化的外膜肽标签结合到沉积的 TiO 上。使用 TMPD（N,N,N',N'-四甲基-p-苯二胺）作为电解质，这些生物杂化光活性电极产生的输出是阴极和阳极光电流的净产物。为了解释观察到的光电流，提出了一个包含以下内容的动力学模型：（1）阳极电流归因于 RC 初级电子供体（P）的三重态电子注入 TiO 导带，（2）阴极电流归因于 TiO 表面态还原光氧化的 RC 初级电子供体（P），以及（3）由于导电玻璃（FTO）衬底上的 TMPD/TMPD 的氧化/还原而产生的瞬态阴极和阳极电流尖峰。该模型解释了在打开或关闭照明后出现在该系统中的光电流尖峰的起源，以及根据实验条件出现净正或负稳定光电流的原因，以及构建电池的整体效率。该模型可用于指导改进所提出系统的光电流效率，以及在进行适当调整后，用于其他生物杂化光电极。
