In this article, the potential of biophotovoltaic devices (BPVs) as a sustainable solution for addressing the global energy crisis and combating climate change is explored. BPVs harness renewable ...electricity from sunlight and water through the photosynthetic activity of microorganisms, such as cyanobacteria and algae, serving as living photocatalysts. The focus is primarily on enhancing photocurrent outputs by developing efficient anode materials. Carbon‐based electrodes, particularly graphene (Gr), emerge as promising candidates due to their cost‐effectiveness, electrical conductivity, and mechanical strength. Despite reduced graphene oxide being commonly used, unoxidized Gr has not been extensively explored until recent research demonstrating its excellent current harvesting capacities. Additionally, 1D‐structured nanomaterials, such as electrospun nanofibers, show potential in promoting electron transport and enhancing charge collection efficiency. An innovative photoanode design is introduced, utilizing cyanobacteria immobilized on a cellulose acetate/Gr electrospun mat, offering a porous structure conducive to cyanobacterial attachment and efficient electron transfer. A complementary cathode structure, employing aniline‐modified Pt nanoparticles, facilitates the reduction of protons to yield hydrogen gas. Overall, in this study, BPVs’ potential is highlighted as a viable clean energy technology and novel approaches to enhance their efficiency and sustainability are presented.
This study explores that biophotovoltaic devices harness electricity from sunlight and water through photosynthetic cyanobacteria activity. A photoanode is introduced, utilizing cyanobacteria immobilized on a cellulose acetate/graphene electrospun mat, offering a porous structure conducive to cyanobacterial attachment and efficient electron transfer. A cathode structure, employing aniline‐modified Pt nanoparticles, facilitates the proton reduction to yield hydrogen gas.
Display omitted
•Boronic acid modification of C. vulgaris improves the crosslinking with redox polymer.•The bioanode’s action spectrum confirms the photosystems as electron source.•Scanning ...photoelectrochemical microscopy suggests O2 consumption upon illumination.•The bioanode is coupled to a bilirubin oxidase biocathode for a proof-of-concept biophotovoltaic cell.
Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm−2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices.
A transparent biohybrid photoelectrochemical tandem cell is developed by employing optically‐complementary variants of a photosynthetic protein in a stacked tandem architecture that utilizes a ...conductive polymer, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), as a transparent counter electrode. The tandem design demonstrates the photocurrent enhancement by complementary absorption of two naturally‐occurring red and green versions of a bacterial Reaction center/Light Harvesting protein (RC‐LH1) that vary in the type of light harvesting carotenoid feeding the central reaction center module with excited state energy. The use of PEDOT:PSS electrode results in a 12‐fold improvement in photocurrent compared to that achievable with Platinum.
The Cover Feature illustrates an amplitude modulated approach for measuring photocurrent signals (iPC) originating from reaction center proteins bound to a gold surface at any applied potential. This ...approach uses a modulated light intensity signal and a lock‐in amplifier to isolate small photocurrents from large background currents (iDC) due to the redox of the hydroquinone (HQ) sacrificial donor on the uncovered electrode surface. More information can be found in the Article by D. Jun et al. on page 2870 in Issue 11, 2019 (DOI: 10.1002/celc.201900249).
The high quantum efficiency of photosynthetic reaction centers (RCs) makes them attractive for bioelectronic and biophotovoltaic applications. However, much of the native RC efficiency is lost in ...communication between surface-bound RCs and electrode materials. The state-of-the-art biophotoelectrodes utilizing cytochrome c (cyt c) as a biological wiring agent have at best approached 32% retained RC quantum efficiency. However, bottlenecks in cyt c-mediated electron transfer have not yet been fully elucidated. In this work, protein film voltammetry in conjunction with photoelectrochemistry is used to show that cyt c acts as an electron-funneling antennae that shuttle electrons from a functionalized rough silver electrode to surface-immobilized RCs. The arrangement of the two proteins on the electrode surface is characterized, revealing that RCs attached directly to the electrode via hydrophobic interactions and that a film of six cyt c per RC electrostatically bound to the electrode. We show that the additional electrical connectivity within a film of cyt c improves the high turnover demands of surface-bound RCs. This results in larger photocurrent onset potentials, positively shifted half-wave reduction potentials, and higher photocurrent densities reaching 100 μA cm
. These findings are fundamental for the optimization of bioelectronics that utilize the ubiquitous cyt c redox proteins as biological wires to exploit electrode-bound enzymes.
The discovery of extracellular electron conduits has spurred new applications in microbial electronics. Except for a limited number of exoelectrogens, most microbes are surrounded by insulating ...membranes that impair extracellular electron transfer. This study focuses on the fabrication of a conductive polypyrrole (PPy) coating for enhancing microbial charge extraction. The polymer deposition is characterized and optimized using a combination of potentiodynamic and potentiostatic measurements as well as scanning electron microscopy (SEM), energy dispersive X‐Ray (EDX) analysis, and Raman spectroscopy. The electrodes are used to extract photosynthetic electrons from the cyanobacteria Synechocystis sp. PCC6803 (Synechocystis) and Synechococcus Elongatus PCC7942 (Elongatus). The PPy electrode shows a sixfold increase in extracted photocurrent for Synechocystis under unmediated conditions compared to bare graphite electrodes. This enhancement is attributed to the decreased resistance and increased electroactive surface area of the PPy electrode. By contrast, Elongatus shows no substantial difference in photocurrent between the PPy and bare electrodes. Compared to Synechocystis cells, the Elongatus cells show limited electrode adherence with weaker charge interactions. These findings lay the framework for designing customized polymer electrodes for strain‐specific charge extraction.
This study focuses on using a conductive polypyrrole coating for enhancing microbial charge extraction from cyanobacteria Synechocystis sp. PCC6803 and Synechococcus Elongatus PCC7942. Synechocystis cells show a sixfold increase in extracted photocurrent contrary to the Elongatus cells that exhibit limited electrode adherence and weaker charge interactions. These findings lay the framework for designing customized polymer electrodes for strain‐specific charge extraction.
Live cyanobacteria and algae integrated onto an extracellular electrode can generate a light-induced current (i.e., a photocurrent). Although the photocurrent is expected to be correlated with the ...redox environment of the photosynthetic cells, the relationship between the photocurrent and the cellular redox state is poorly understood. Here, we investigated the effect of the reduced nicotinamide adenine dinucleotide phosphate NADP(H) redox level of cyanobacterial cells (before light exposure) on the photocurrent using several mutants (Δ
zwf
, Δ
gnd
, and Δ
glgP
) deficient in the oxidative pentose phosphate (OPP) pathway, which is the metabolic pathway that produces NADPH in darkness. The NAD(P)H redox level and photocurrent in the cyanobacterium
Synechocystis
sp. PCC 6803 were measured noninvasively. Dysfunction of the OPP pathway led to oxidation of the photosynthetic NADPH pool in darkness. In addition, photocurrent induction was retarded and the current density was lower in Δ
zwf
, Δ
gnd
, and Δ
glgP
than in wild-type cells. Exogenously added glucose compensated the phenotype of Δ
glgP
and drove the OPP pathway in the mutant, resulting in an increase in the photocurrent. The results indicated that NADPH accumulated by the OPP pathway before illumination is a key factor for the generation of a photocurrent. In addition, measuring the photocurrent can be a non-invasive approach to estimate the cellular redox level related to NADP(H) pool in cyanobacteria.
The photosynthetic activities of cyanobacteria have been employed in various energy related fields such as energy harvesting and water-splitting based energy conversion. However, the output powers ...obtained from the photo-bioelectrochemical cells have lower efficiency than those from other artificial materials. It is reported in this study that Synechococcus sp.-iron oxide nanoparticles (γ-Fe2O3 and Fe3O4)- neodymium iron boride magnet complexes enable great energy harvesting performance by both synergistic combination effect of the natural and artificial photocatalysts and formation of an effective electron transfer conduit to the electrode. A green LED bulb is turned on as the result of the energy harvesting. During the light illumination, electrons are transported through the electrode, yielding a peak power density of 0.806 and 0.534 W/m2 for Synechococcus sp.-γ-Fe2O3- neodymium iron boride magnet and Synechococcus sp.-Fe3O4- neodymium iron boride magnet complexes, respectively. The difference in the power output arises from the distinct electrochemical interactions among the cell, iron oxide nanoparticles, and NdFeB depending on the type of the nanoparticles. The approach introduced in this study can boost solar energy harvesting remarkably by combining natural photocatalysts with artificial ones.
•Anomalous power enhancement was achieved by a novel bioinorganic hybrid system.•Biophotovoltaic complexes were fabricated based on the properties of components.•The natural and artificial photocatalysts form an electron conduit to the electrode.•A green LED bulb is turned on as the result of the energy harvesting.
Display omitted
•Serial algae fuel cell stack generated power from wastewater and light.•Voltage reversal blocked by computerized method.•Light and assisted aeration resolved voltage ...reversal.•Blackout starvation, immediate and slow light starvation were distinguished.•Light starvation correlated with oxygen reduction rate at bio interphase.
Stacked algae microbial fuel cells (AMFC) combine the strategic use of light and microbial energy to generate usable electricity. It generates oxygen directly at the electrodes, providing CO2 cycling, algal biomass, and value-added biomolecules. In this work a 12 Liter LED-Algae-Microbial-Fuel-Cell-Stack with maximum power tracking was investigated for voltage balancing and reversal resolution, enabling up to 1200 mV stable stack voltage under closed circuit conditions. The experiment was run in a municipal wastewater treatment plant for 152 days. A new type of data control computer device was used to block voltage reversals and maintaining power with unit resistances between 42 and 99 Ohm. It also allowed the detection of previously unreported light starvation effects in 16 process variants with voltage drops ranging from 14 to 240 mV switching off lights. Algae generated an oxygen concentration of 1.9–3.7 mg/L during power generation. Extending all light-on conditions significantly reduced the voltage reversal frequency. All light-on in combination with assisted oxygenation using 0.25 L/min air bubbling per unit resolved voltage reversals and balanced the AMFC-Stack.
The results obtained are relevant to the study of stacked bioelectric systems that use low substrate concentrations and yet aim to generate stable power and minimize voltage reversals.
Herein, results of photoinduced pH oscillatory phenomena of microalgae in laboratory systems are presented. Microalgae are an extremely complex biomaterial in which light‐induced quantum mechanical ...processes induce changes in the surrounding aqueous environment (medium). A phenomenological understanding of the photoresponse by a quantitative study of pH oscillations of the medium is provided. The biochemical processes of algal metabolism and photosynthesis and the impact of light on a nitrate‐enriched medium are examined. pH variations in the external medium and the impact on future applications of microalgae are presented. External pH dominantly impacts conductivity in the solution of algal biophotovoltaic devices. This is the first dynamic study of the light‐induced pH behavior of microalgae with direct relevance to carbon capture, biophotovoltaic electricity generation, and quantum photosynthesis.
Herein, the photoresponse of microalgae systems via unique time‐dependent pH oscillatory phenomena is presented. The goal of this research is to understand the dynamics of photosynthetic biomaterials in large controlled biochemical systems. It intends to provide applications in areas ranging from carbon capture to biophotovoltaics and rapid phenomenological methods for the study of quantum photosynthesis.
PDF
