Photosynthetic pigment–proteins exhibit an excellent ability to transduce solar energy to electrical energy with high quantum efficiency. In article number 1601821, Swee Ching Tan and co‐workers ...report a tandem design demonstrating the photocurrent enhancement by complementary absorption of the red and green variants of a bacterial Reaction Center/Light Harvesting protein that vary in the absorption characteristics of the carotenoid.
Microbial extracellular electron transfer (EET) to solid-state electron acceptors such as anodes and metal oxides, which was originally identified in dissimilatory metal-reducing bacteria, is a key ...process in microbial electricity generation and the biogeochemical cycling of metals. Although it is now known that photosynthetic microorganisms can also generate (photo)currents via EET, which has attracted much interest in the field of biophotovoltaics, little is known about the reduction of metal (hydr)oxides via photosynthetic microbial EET. The present work quantitatively assessed the reduction of ferrihydrite in conjunction with the EET of the photosynthetic microbe
sp. PCC 6803. Microbial reduction of ferrihydrite was found to be initiated in response to light but proceeded at higher rates when exogenous glucose was added, even under dark conditions. These results indicate that current generation from
cells does not always need light irradiation. The qualitative trends exhibited by the ferrihydrite reduction rates under various conditions showed significant correlation with those of the microbial currents. Notably, the maximum concentration of Fe(II) generated by the cyanobacterial cells under dark conditions in the presence of glucose was comparable to the levels observed in the photic layers of Fe-rich microbial mats.
In article number 1805521, Massimo Trotta, Gianluca M. Farinola, and co‐workers discuss the use of photosynthetic and photoresponsive bacteria as a source of materials for optoelectronics and ...photonic devices. Emphasis on new concepts in materials design and device architectures emerging from recent research is given.
Emulation of natural photosynthesis is central to modern photovoltaic research targeting sustainable and economic ways of solar energy harvesting. Natural photosynthetic systems have succeeded in ...efficiently harvesting solar energy which is key to the sustenance of life on earth. With numerous advances in understanding the structure and function of the natural photosystems, the last decade has witnessed new perspectives in developing bioinspired photovoltaics. Interestingly, organic photovoltaics (OPVs) adopting photosynthetic design principles and biophotovoltaics (BPVs) adopting solid‐state device architectures have now converged at a juncture. Several reports in recent years point to a new scope of improvement in OPVs and BPVs stemming from mutual inspiration. At this juncture, there are new perspectives by which a BPV can be designed that were previously limited only to conventional optoelectronics. Treating natural pigment–proteins as optically and electronically functional materials in any photovoltaic design, from the band‐theory viewpoint, is a promising direction for advancing BPVs beyond the boundaries of bioelectrochemistry. This article presents an overview of selected reports on BPVs in the last few years utilizing new design concepts based on band‐theory and its associated principles. In light of this, the scope of the band‐structure approach in BPVs is discussed, eliciting prospective research directions.
The electronic processes in natural photosynthetic systems are reviewed, and a contrast is established with emerging photovoltaic systems, thereby providing insight on how the band‐structure approach can aid in bridging photosynthetic research and emerging photovoltaic technologies by mutual inspiration.
Well‐defined assemblies of photosynthetic protein complexes are required for an optimal performance of semi‐artificial energy conversion devices, capable of providing unidirectional electron flow ...when light‐harvesting proteins are interfaced with electrode surfaces. We present mixed photosystem I (PSI) monolayers constituted of native cyanobacterial PSI trimers in combination with isolated PSI monomers from the same organism. The resulting compact arrangement ensures a high density of photoactive protein complexes per unit area, providing the basis to effectively minimize short‐circuiting processes that typically limit the performance of PSI‐based bioelectrodes. The PSI film is further interfaced with redox polymers for optimal electron transfer, enabling highly efficient light‐induced photocurrent generation. Coupling of the photocathode with a NiFeSe‐hydrogenase confirms the possibility to realize light‐induced H2 evolution.
Towards the development of improved biophotovoltaic devices for solar energy conversion, a mixed monolayer constituted by photosystem I trimers and monomers enables the fabrication of highly efficient biophotoelectrodes by minimizing electronic short‐circuiting processes while at the same time ensuring a high density of photoactive molecules per unit area.
Microbial fuel cells and biophotovoltaics represent promising technologies for green bioelectricity generation. However, these devices suffer from low durability and efficiency that stem from their ...reliance on living organisms to act as catalysts. Such limitations can be overcome with augmented capabilities enabled by nanotechnology. This review presents an overview of the different nanomaterials used to enhance bioelectricity generation through improved light harvesting, extracellular electron transfer, and anode performance. The implementation of nanomaterials in whole-cell energy devices holds promise in developing bioelectrical devices that are suitable for industry.
Biophotovoltaic systems (BPVs) resemble microbial fuel cells, but utilise oxygenic photosynthetic microorganisms associated with an anode to generate an extracellular electrical current, which is ...stimulated by illumination. Study and exploitation of BPVs have come a long way over the last few decades, having benefited from several generations of electrode development and improvements in wiring schemes. Power densities of up to 0.5 W m−2 and the powering of small electrical devices such as a digital clock have been reported. Improvements in standardisation have meant that this biophotoelectrochemical phenomenon can be further exploited to address biological questions relating to the organisms. Here, we aim to provide both biologists and electrochemists with a review of the progress of BPV development with a focus on biological materials, electrode design and interfacial wiring considerations, and propose steps for driving the field forward.
Forward thinking: Biophotovoltaic (BPV) systems utilise oxygenic photosynthetic microorganisms associated with an anode to generate an extracellular electrical current, which is stimulated by illumination. The aim of this Minireview is to provide both biologists and electrochemists with an overview of the progress of BPV development with a focus on biological materials, electrode design and interfacial wiring considerations, and propose steps for driving the field forward.
The prevalence of photosynthesis, as the major natural solar energy transduction mechanism or biophotovoltaics (BPV), has always intrigued mankind. Over the last decades, we have learned to extract ...this renewable energy through continuously improving solid-state semiconductive devices, such as the photovoltaic solar cell. Direct utilization of plant-based BPVs has, however, been almost impracticable so far. Nevertheless, the electrochemical platform of fuel cells (FCs) relying on redox potentials of algae suspensions or biofilms on functionalized anode materials has in recent years increasingly been demonstrated to produce clean or carbon-negative electrical power generators. Interestingly, these algal BPVs offer unparalleled advantages, including carbon sequestration, bioremediation and biomass harvesting, while producing electricity. The development of high performance and durable BPVs is dependent on upgraded anode materials with electrochemically dynamic nanostructures. However, the current challenges in the optimization of anode materials remain significant barriers towards the development of commercially viable technology. In this context, two-dimensional (2D) graphene-based carbonaceous material has widely been exploited in such FCs due to its flexible surface functionalization properties. Attempts to economically improve power outputs have, however, been futile owing to molecular scale disorders that limit efficient charge coupling for maximum power generation within the anodic films. Recently, Langmuir-Blodgett (LB) film has been substantiated as an efficacious film-forming technique to tackle the above limitations of algal BPVs; however, the aforesaid technology remains vastly untapped in BPVs. An in-depth electromechanistic view of the fabrication of LB films and their electron transference mechanisms is of huge significance for the scalability of BPVs. However, an inclusive review of LB films applicable to BPVs has yet to be undertaken, prohibiting futuristic applications. Consequently, we report an inclusive description of a contextual outline, functional principles, the LB film-formation mechanism, recent endeavors in developing LB films and acute encounters with prevailing BPV anode materials. Furthermore, the research and scale-up challenges relating to LB film-integrated BPVs are presented along with innovative perceptions of how to improve their practicability in scale-up processes.
Photosystem I (PSI), a robust and abundant biomolecule capable of delivering high‐energy photoelectrons, has a great potential for the fabrication of light‐driven semi‐artificial bioelectrodes. ...Although possibilities have been explored in this regard, the true capabilities of this technology have not been achieved yet, particularly for their use as bioanodes. Here, the use of PSI Langmuir monolayers and their electrical wiring with specifically designed redox polymers is shown, ensuring an efficient mediated electron transfer as the basis for the fabrication of an advanced biophotoanode. The bioelectrode is rationally implemented and optimized for enabling the generation of substantial photocurrents of up to 17.6 µA cm−2 and is even capable of delivering photocurrents at potentials as low as −300 mV vs standard hydrogen electrode, surpassing the performance of comparable devices. To highlight the applicability of the developed light‐driven bioanode, a biophotovoltaic cell is assembled in combination with a gas‐breathing biocathode. The assembly operates in a single compartment cell and delivers considerable power outputs at large cell voltages. The implemented biophotoanode constitutes an important step toward the development of advanced biophotovoltaic devices.
An advanced bioelectrode is fabricated by interfacing photosystem I Langmuir monolayers electrically wired with specifically designed redox polymers. The resultant biophotoanode is rationally optimized for improved performance by overcoming potential limitations and short‐circuiting processes commonly associated with the use of isolated photosystems. A biophotovoltaic device is further implemented in combination with a gas‐breathing biocathode, showing the applicability of the biophotoelectrode.
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