Solar Energy Conversion through Thylakoid Membranes Wired by Osmium Redox Polymer and Indium Tin Oxide Nanoparticles

Abstract

For several decades, much attention has been paid to thylakoid membranes (TMs) as photocatalysts for converting solar light to electricity. Despite extensive research, current technology provides only limited photocurrents. Here, a novel method based on TM-composite material was developed for achieving high photocurrent. When a thin film composed of TMs, osmium redox polymer (Os-RP), and indium tin oxide nanoparticles (ITOnp) was formed on a porous graphite surface, appreciable photocurrent as high as 0.5 mA cm À 2 was achieved at 0.4 V vs. Ag/AgCl. Each component plays its own role in transferring electrons from TMs to the anode, resulting in sharp drop in photocurrent with missing any component. Optimization between these three components showed 1 : 0.5 : 30 (TM/Os-RP/ ITOnp) was the best ratio. Action spectra confirmed that TMs was the origin of photocurrent. It was inferred from blocking experiments using 3-(3,4-dichlorophenyl)-1,1-dimethylurea as an inhibitor that about 41 % of photocurrent was transferred from Q A in photosystem II to the electrode via Os-RP and ITOnp. Quantum efficiencies at 430 and 660 nm were 12.2 and 18.5 %, respectively. Turnover frequency for water oxidation depended upon the amount of the composite. A complete cell with Pt/C cathode produced P max of 122 μW cm À 2 at 758 μA cm À 2 under one sun illumination, which is the highest power density to our knowledge. This study opened a possibility of using TMs as photocatalysts for solar energy conversion.

MnO2-decorated highly porous 3D-printed graphene supercapacitors for photosynthetic power systems

“…70–78 Regarding the PE current density of this system, the highest PE current density among recent studies was achieved in this work as shown in Fig. S7 † 10–14,29–33,79–84.…”

“…S7. † [10][11][12][13][14][29][30][31][32][33][79][80][81][82][83][84] For efficient collection of PEs from TMs, TMs need to be attached and electrically connected to a 3D printed graphene electrode. However, since TMs have abundant ionized side groups, they do not form stable bonds with graphene electrodes that are hydrophobic.…”

Closing the green gap of photosystem I with synthetic fluorophores for enhanced photocurrent generation in photobiocathodes

“…Successful setups have been achieved with PSI, 1,5,7,[11][12][13][14][15] PSII, 9,[16][17][18][19][20][21] and bacterial reaction centers. 4,8,[22][23][24][25] But likewise, thylakoid membranes [26][27][28] and even whole cells [29][30][31][32] have been deployed effectively.…”

“…Many electrode materials and constructions have been applied as the synthetic part in contact with the biological entity. Metals, alloys, and metal oxides such as gold, 8,11,24,33,34 silver, 22 indium bismuth tin, 31 antimony tin oxide (ATO), 25,35 indium tin oxide (ITO), 14,21,28,[36][37][38] titanium dioxide, 16,20,39,40 zinc oxide, 8,29 and zirconium dioxide 39 as well as many carbon-based materials 1,11,21,41,42 have been utilized successfully. It is important to note that not only at 2D electrodes have been produced, 24,34,43 but also thicker architectures including multilayers, 13,14,24,33 hydrogels, 1,7,23 and 3D setups.…”

“…As a dened orientation of large photosystems is difficult to achieve, oen redox-active molecules have been used to shuttle electrons. Examples for these mediators are small redox molecules, 5,18,26,30,32,42 redox polymers 17,19,23,27,28,32,34 or different cytochromes. 12,22,27,35,36,45 The renunciation of redox mediators and, a Biosystems Technology, Technical University of Applied Sciences Wildau, Hochschulring 1, 15745 Wildau, Germany.…”