Baker David R, Simmerman Richard F, Sumner James J, Bruce Barry D, Lundgren Cynthia A
U.S. Army Research Laboratory, Sensors and Electron Devices Directorate, Adelphi, Maryland 20783, United States.
Langmuir. 2014 Nov 18;30(45):13650-5. doi: 10.1021/la503132h. Epub 2014 Nov 6.
Developing a solid state Photosystem I (PSI) modified electrode is attractive for photoelectrochemical applications because of the quantum yield of PSI, which approaches unity in the visible spectrum. Electrodes are constructed using a Nafion film to encapsulate PSI as well as the hole-scavenging redox mediator Os(bpy)2Cl2. The photoactive electrodes generate photocurrents of 4 μA/cm(2) when illuminated with 1.4 mW/cm(2) of 676 nm band-pass filtered light. Methyl viologen (MV(2+)) is present in the electrolyte to scavenge photoelectrons from PSI in the Nafion film and transport charges to the counter electrode. Because MV(2+) is positively charged in both reduced and oxidized states, it is able to diffuse through the cation permeable channels of Nafion. Photocurrent is produced when the working electrode is set to voltages negative of the Os(3+)/Os(2+) redox potential. Charge transfer through the Nafion film and photohole scavenging at the PSI luminal surface by Os(bpy)2Cl2 depends on the reduction of Os redox centers to Os(2+) via hole scavenging from PSI. The optimal film densities of Nafion (10 μg/cm(2) Nafion) and PSI (100 μg/cm(2) PSI) are determined to provide the highest photocurrents. These optimal film densities force films to be thin to allow the majority of PSI to have productive electrical contact with the backing electrode.
开发一种固态光系统I（PSI）修饰电极对于光电化学应用具有吸引力，因为PSI的量子产率在可见光谱中接近1。使用Nafion膜构建电极，以封装PSI以及空穴清除氧化还原介质Os(bpy)2Cl2。当用1.4 mW/cm(2)的676 nm带通滤波光照射时，光活性电极产生4 μA/cm(2)的光电流。电解质中存在甲基紫精（MV(2+)），以从Nafion膜中的PSI清除光电子并将电荷传输到对电极。由于MV(2+)在还原态和氧化态均带正电，它能够通过Nafion的阳离子渗透通道扩散。当工作电极设置为低于Os(3+)/Os(2+)氧化还原电位的电压时会产生光电流。通过Nafion膜的电荷转移以及Os(bpy)2Cl2在PSI腔表面的光空穴清除取决于通过从PSI清除空穴将Os氧化还原中心还原为Os(2+)。确定Nafion（10 μg/cm(2) Nafion）和PSI（100 μg/cm(2) PSI）的最佳膜密度以提供最高的光电流。这些最佳膜密度迫使膜变薄，以使大多数PSI与背电极进行有效的电接触。
