Abstract
We demonstrate photovoltaic activity of electrodes composed of fluorine-doped tin oxide (FTO) conducting glass and a multilayer of trimeric photosystem I (PSI) from cyanobacterium Synechocystis sp. PCC 6803 yielding, at open circuit potential (OCP) of + 100 mV (vs. SHE), internal quantum efficiency of (0.37 ± 0.11)% and photocurrent density of up to (0.5 ± 0.1) µA/cm2. The photocurrent measured for OCP is of cathodic nature meaning that preferentially the electrons are injected from the conducting layer of the FTO glass to the photooxidized PSI primary electron donor, P700+, and further transferred from the photoreduced final electron acceptor of PSI, Fb−, via ascorbate electrolyte to the counter electrode. This observation is consistent with preferential donor-side orientation of PSI on FTO imposed by applied electrodeposition. However, by applying high-positive bias (+ 620 mV) to the PSI-FTO electrode, exceeding redox midpoint potential of P700 (+ 450 mV), the photocurrent reverses its orientation and becomes anodic. This is explained by “switching off” the natural photoactivity of PSI particles (by the electrochemical oxidation of P700 to P700+) and “switching on” the anodic photocurrent from PSI antenna Chls prone to photooxidation at high potentials. The efficient control of the P700 redox state (P700 or P700+) by external bias applied to the PSI-FTO electrodes was evidenced by ultrafast transient absorption spectroscopy. The advantage of the presented system is its structural simplicity together with in situ-proven high intactness of the PSI particles.
Highlights
Solar cells are desirable but still relatively expensive devices for the electrical energy production
We present photovoltaic data obtained from the system containing simple photosystem I (PSI)-fluorine-doped tin oxide (FTO) photoelectrode identical to that one described in Szewczyk et al (2017, 2018) and propose a mechanism of the anodic and cathodic photocurrent generation in this system
The data were recorded for open circuit potential (OCP) = + 100 mV, which was the potential applied to working electrode (WE) blocking any dark current but not photocurrent
Summary
Solar cells are desirable but still relatively expensive devices for the electrical energy production. Many attempts have been undertaken to discover new technologies of solar energy conversion. Utilization of biological light-converting systems, in particular those involved in natural photosynthesis, is often postulated to be the promising direction of research (Kornienko et al 2018). 2001; Amunts et al 2007; Qin et al 2015, 2019), is a natural and very efficient biological converter of light energy into the energy of electrical current. Its quantum efficiency of absorbed photon to electron conversion exceeds 99% and the voltage generated after light-induced charge separation (electron transfer) between the primary and final redox cofactors inside PSI is ~ 1 V. PSI is often used as a photosensitive component of different types of working photoelectrodes being a part of prototype biosolar cells (Robinson et al 2018; Musazade et al 2018; Friebe and Frese 2017; Milano et al 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
