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. 2021 May 12;7(20):eabf2543.
doi: 10.1126/sciadv.abf2543. Print 2021 May.

Enhanced interfacial electron transfer between thylakoids and RuO2 nanosheets for photosynthetic energy harvesting

Hyeonaug Hong  1 , Jang Mee Lee  2 , JaeHyoung Yun  1 , Yong Jae Kim  1 , Seon Il Kim  1 , HyeIn Shin  1 , Hyun S Ahn  3 , Seong-Ju Hwang  4 , WonHyoung Ryu  5
Affiliations

Enhanced interfacial electron transfer between thylakoids and RuO2 nanosheets for photosynthetic energy harvesting

Hyeonaug Hong et al. Sci Adv. .

Abstract

The harvesting of photosynthetic electrons (PEs) directly from photosynthetic complexes has been demonstrated over the past decade. However, their limited efficiency and stability have hampered further practical development. For example, despite its importance, the interfacial electron transfer between the photosynthetic apparatus and the electrode has received little attention. In this study, we modified electrodes with RuO2 nanosheets to enhance the extraction of PEs from thylakoids, and the PE transfer was promoted by proton adsorption and surface polarity characteristics. The adsorbed protons maintained the potential of an electrode more positive, and the surface polarity enhanced thylakoid attachment to the electrode in addition to promoting ensemble docking between the redox species and the electrode. The RuO2 bioanode exhibited a five times larger current density and a four times larger power density than the Au bioanode. Last, the electric calculators were successfully powered by photosynthetic energy using a RuO2 bioanode.

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Figures

Fig. 1
Fig. 1. Enhanced interfacial electron transfer through RuO2 NSs.
(A) Schematic of PE harvesting with RuO2 bioanode. ATP, adenosine 5′-triphosphate. (B) Proton adsorption characteristic of RuO2 NS result in positive electrode potential. (C) Adhesion enhancement by electrostatic interactions between RuO2 NS and TMs. (D) Ensemble docking induced by RuO2 NS to electron carrier and PS.
Fig. 2
Fig. 2. Electrode potential of electrodes.
(A) Electrode potential of Au and RuO2 electrodes without and with thylakoid and during PEs harvesting. ***Student’s t test, P < 0.001 and n = 5 for statistical analysis. (B) Midpoint potential of electron carriers on PET chain of thylakoid. Oxygen evolution complex (OEC), tyrosine (Tyrz), pheophytin (pheo), primary and secondary acceptor quinone (QA and QB), chlorophyll (A0), and pylloquinone (A1).
Fig. 3
Fig. 3. Photosynthetic currents measured from Au and RuO2 bioanodes.
(A) Photosynthetic currents with 10 mW cm−1 of light intensity and 400 mV of bias potential. (B) Mediated PEs harvesting through potassium ferricyanide. (C) PE currents depending on light intensity with 400 mV bias potential. (D) Dependency of PE currents on the bias potential with 10 mW cm−1 of light intensity. Photosynthetic current before and after 1 mM 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) addition to (E) Au bioanode and (F) RuO2 bioanode.
Fig. 4
Fig. 4. Fourier-filtered k3-weighted Ru K-edge EXAFS oscillations and their FT data.
(A and B) In situ Fourier-filtered Ru K-edge EXAFS data and (C and D) their FT of the (A and C) RuO2-thylakoid and (B and D) RuO2 films before (black) and after (red) the light illumination.
Fig. 5
Fig. 5. Photosynthetic electrochemical cell for energy harvesting.
(A) Schematic of photosynthetic energy harvesting. (B) Polarization curve of cells during photosynthesis. (C) OCV of cells. ***Student’s t test, P < 0.001 and n = 5 for statistical analysis. (D) Dependency of maximum power on the light intensity.
Fig. 6
Fig. 6. Performance of the multiple connected photosynthetic electrochemical cells to operate a small calculator.
(A) Conceptual figure of multiple connected photosynthetic electrochemical cells. (B) Images of cells under light off (left) and on (right). (C) The captured image of the calculator used here. (D) OCVs with and without illumination when the calculator is off. (E) Currents under the same conditions as (D). (F to H) Voltage (left, black line) and current (right, blue line) graphs when the calculator is off and on (F) without illumination, (G) with illumination, and (H) after leakage current suppressing by disconnecting the calculator. Photo credit: Hyeonaug Hong, Yonsei University.
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