Photosystem I Multilayers within Porous Indium Tin Oxide Cathodes Enhance Mediated Electron Transfer

Abstract

Understanding and improving charge transfer pathways between extracted Photosystem I (PSI) protein complexes and electrodes is necessary for the development of low‐cost PSI‐based devices for energy conversion. We incorporated PSI multilayers within porous indium tin oxide (ITO) electrodes and observed a greater mediated photocurrent in comparison to multilayers on planar ITO. First, the mediated electron transfer (MET) pathway in the presence of 2,6‐dichlorophenolindophenol (DCPIP) and ascorbate (AscH) was studied via photochronoamperometry on planar ITO. ITO nanoparticles were then used to fabricate two porous electrode morphologies; mesoporous (20–100 nm pores) and macroporous (5 μm pores). PSI multilayers within macroporous ITO cathodes produced 42±5 μA cm−2 of photocurrent, three times the photocurrent produced by mesoporous ITO. Additionally, macroporous cathodes are able to utilize twice as much active surface area, when compared to mesoporous cathodes. Our findings show that MET within PSI multilayers is greater in 5 μm macropores than mesoporous ITO due to both an increase in electrode surface area and the location of PSI complexes within the pores. Improving MET in PSI‐based bioelectrodes has applications including improving the total charge transfer achieved in PSI‐based photoelectrochemical cells or even incorporation in bio‐photocatalytic cells.

Rational design of artificial redox-mediating systems toward upgrading photobioelectrocatalysis

“…For example, the theoretical current capacity of biophotovoltaic cells containing cyanobacteria is postulated to range in the orders of 0.07-0.77 mW cm −2 whereas their empirical values typically average in the 0.0001-0.01 mW cm −2 range [6,40]. Technological advances in terms of improving anode design and cell architecture to implement better photosynthetic entity binding, film loading, increased electroactive surface area, mass transport capabilities and light transmittance have been reported [19,[41][42][43]. On the other hand, redox mediation for long-range EET in semiartificial photosynthetic systems (E-MET), can be broadly classified into two, namely; exogenous diffusible redox mediators (Fig.…”

“…4) [65]. The paired system is utilized since DCPIPH 2 , obtained after ascorbic acid oxidation and two-proton-two-electron transfer to DCPIP, is an efficient electron donor for the P 700 + redox active center [43,66]. Comparatively, ascorbate alone is a poorly efficient electron donor for P 700 + , even at high concentrations [67][68][69].…”

“…Comparatively, ascorbate alone is a poorly efficient electron donor for P 700 + , even at high concentrations [67][68][69]. There is extensive literature on the use of the DCPIP/ascorbate pair as a sacrificial agent or for redox mediation [6,36,43,[70][71][72][73][74][75][76][77][78][79]. The popularity of DCPIP is partially attributed to PSI enzymes being one of the most frequently used photosynthetic entities in biophotovoltaic systems, with which DCPIP shares bio-and redox potential compatibility.…”

Membrane Protein Modified Electrodes in Bioelectrocatalysis

“…The effect of pore size was studied by comparing photocurrents between mesoporous (20-100 nm) and macroporous (5 µm) electrodes using 2,6-dichlorophenolindophenol (DCPIP) and ascorbate as redox mediator for PSI. The macroporous electrode showed three times higher photocurrent than the mesoporous electrode [96]. The authors observed that the macroporous electrode increased the active surface area twice compared to the mesoporous electrode with the same PSI mass loading.…”

Photosystem I Enhances the Efficiency of a Natural, Gel-Based Dye-Sensitized Solar Cell

“…PSI is known to improve the photoelectrochemical performance of many electrode materials under various conditions. − Photoelectrochemical investigations of PSI have commonly used a three-electrode liquid cell to enable a focused study of the photoelectrochemical interface between PSI and a single electrode. ,, In contrast, fewer researchers have reported the use of PSI in a two-electrode solar cell, − and most of these include solid-state devices. − ,, Solid-state devices with PSI depend on direct electron transfer from electrodes or conducting materials to and from the P 700 and F B sites, which complicates device fabrication in comparison to devices dependent on mediated electron transfer (MET). Alternatively, liquid cells rely on MET, in which redox reactions occur throughout a protein film as reactants freely diffuse to the electrodes …”