Modelling of the cathodic and anodic photocurrents from Rhodobacter sphaeroides reaction centres immobilized on titanium dioxide

Abstract

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 TiO2 by natural pigment-protein complexes rather than an artificial dye. Rba. sphaeroides RCs were bound to the deposited TiO2 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 (PT) to the TiO2 conduction band, (2) a cathodic current attributed to reduction of the photooxidized RC primary electron donor (P+) by surface states of the TiO2 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.Electronic supplementary materialThe online version of this article (10.1007/s11120-018-0550-8) contains supplementary material, which is available to authorized users.

A Biological-Based Photovoltaic Electrochemical Cell: Modelling the Impedance Spectra

“…On the other side, there is a growing interest in mimicking sunlight energy conversion occurring in the natural photosynthetic process, such as in the Grätzel cell [1]. More recently, photoactive proteins extracted from plants, bacteria, and archaea [2][3][4][5] have been tested with the aim of producing biological-based photoelectrochemical cells (bPECs). In particular, much interest is devoted to the reaction center (RC) isolated from the purple photosynthetic bacterium Rhodobacter sphaeroides, thanks to its simple extraction and purification procedure, stability outside its natural environment, and large possibility of genetic manipulation for mutant construction [6].…”

Excitation dynamics in Photosystem I trapped in TiO2 mesopores

“…Preparation of the TiO 2 pastes was the same as that one already described (Białek et al 2018). For fluorescence measurements, the paste was prepared from 50-nm anatase nanoparticles (MKnano, 98% pure) with a procedure described by Woronowicz et al (Woronowicz et al 2012).…”

Porous silicon pillar structures/photosynthetic reaction centre protein hybrid for bioelectronic applications

“…Various biological systems-at any level of the organisation (e.g. cells, membrane fragments, molecular complexes)-have been used to create different approaches based on light excitation [38][39][40][41][42][43][44][45]. Photosynthetic reaction centre proteins (RCs) are of special interest due to their exceptionally high quantum yield of energy conversion [46].…”