Thylakoid membranes have been proposed for electrochemical solar energy conversion, but they have been plagued with short term instability. In this paper, thylakoid membranes extracted from Spinacia oleracea were physically adsorbed onto Toray paper electrodes with and without catalase, followed by entrapment in a vapor deposited silica matrix. The bioelectrodes were tested using voltammetry and amperometry and tested in a complete photobioelectrochemical cell. Upon subsequent polarization experiments, a significant decrease in the maximum current density from 1.53 ± 0.13 μAcm −2 to 0.75 ± 0.14 μAcm −2 was observed without catalase present. When catalase was included in the anode, this current decrease was not observed, showing the importance of catalase to scavenge reactive oxygen species produced by the thylakoids during photoelectrocatalysis.Thylakoid membranes contain the redox complexes responsible for the light-dependent reactions of photosynthesis found in cyanobacteria and the chloroplasts of plants. They are composed of two photosystems along with several other enzymes and cofactors. Light is absorbed by photosystem II to oxidize water to dioxygen. The electrons produced in the reaction are shuttled to plastoquinone, then cytochrome b 6 f, plastocyanin, and finally photosystem I where they are excited by absorbed photons. 1 They are then used in the reduction of ferredoxin by ferredoxin reductase with the simultaneous conversion of NADP + to NADPH. 2 The protons generated form a proton gradient which allows for the production of ATP, the unit of energy currency in the living cell, by ATP synthase. 1 As the quantum yield for photosynthesis in certain components of thylakoids, specifically photosystem I, is almost 100%, 3 developing a method for using these membranes for photoelectrocatalytic energy conversion in a bio-solar cell is highly desirable.Photovoltaic devices or solar cells are defined as a device capable of converting light (photons) into electrical energy. They are generally constructed of semiconductors and come in a number of varieties, ranging from organic thin film (19.6 ± 0.6% efficiency) and dye sensitized (11.0 ± 0.3%) solar cells (DSSC) to more efficient silicon based (25.0 ± 0.5%) and III-V semiconductor (28.3 ± 0.8%) solar cells. 4 Biological and bio-inspired photoelectrocatalysts have been proposed for solar energy conversion. 5 The bio-inspired photoelectrocatalysts are mostly focused on organometallic complexes with structure inspired by photosystem I or photosystem II, 5a,6 whereas the biological photoelectrocatalysts have focused on either the use of photosystem I 5b,7 or II 8 or the intact thylakoid membranes 5c,9 or chloroplasts. 10 The majority of the literature on photosystem I or II photobioelectrocatalysis and thylakoid photobioelectrocatalysis has employed the use of mediators. 5c,5d,9b However, these mediators typically result in a voltage loss as well as issues associated with their own light, temperature, and long term stability. Therefore, there has been research on d...

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The rapid depletion in global nonrenewable energy stores has prompted a dramatic increase in both academic and industrial research toward alternate means of energy conversion. Although improbable as a single solution to the problem, fuel cells provide many potential contributions in the form of performance combined with scalability. Fuel cells have demonstrated high levels of power production through the consumption of renewable resources in an easily engineered small scale device that operates under mild conditions and could potentially replace today's ubiquitous batteries. Many evaluate energy conversion devices on the basis of the amount of energy converted per unit volume [energy density (Whr/L)] or per unit mass [specific energy (Whr/kg)]. Fuel cells not only rival battery performance in these terms, but also do not require time-consuming charging and do not suffer from the severe hysteresis effects seen in secondary batteries. However, many of these devices use expensive precious metal catalysts that often limit their commercial viability. Passivation by carbon monoxide or other byproducts causes losses in power production over time, and these devices often require high temperatures and harsh conditions to operate efficiently.Thus, many researchers have looked to nature to assist in our current energy conversion needs. Because of biological versatility and efficiency, organisms are able to convert enormous amounts of energy from an incomparable range of chemical substrates. Many researchers have examined ways of harnessing this ability using biofuel cells. Biofuel cells replace the metal catalyst with a biological catalyst: a microbe, enzyme, or even organelle interacting with an electrode surface. 1-3 These types of catalysts offer great benefits in catalytic activity, specificity, and cost. However, development and full evaluation of these dynamic and often sensitive bioelectrochemical systems require a diverse range of expertise. This article will focus on the current techniques used to evaluate the integrity, kinetics, and performance of enzymatic biofuel cells and the applications of the devices. The techniques described span not only the obvious electroanalytical characterization methods needed to evaluate a power source or analytical device, but also common biological and materials characterization techniques. Enzymatic biofuel cells are in an early stage of development, so new analytical techniques are being employed to understand the advantages and limitations of this technology and the engineering design envelope for applications. SPECTROSCOPIC TECHNIQUESEnzymatic biofuel cells employ oxidoreductase enzymes capable of catalyzing redox reactions. Enzymes that are free in solution ROBERT GATES Anal. Chem. 2009, 81, 9538-9545 10

Chitosan, a biopolymer extracted from chitin, was deacetylated by treatment with 45% NaOH followed by autoclaving at 121 °C for a period of 20 minutes. The deacetylated chitosan was then hydrophobically modified via reductive amination with sodium cyanoborohydride and butanal. Glucose dehydrogenase was then co-cast with each polymer on glassy carbon rotating disk electrodes and analysis of mass transfer was executed. Amperometric concentration studies were also carried out to determine catalytic activity of the glucose dehydrogenase enzyme system. The diffusion coefficient governing transport through the air dried film was measured to be 1.42×10 -7 cm 2 /s and 1.08×10 -7 cm 2 /s for butyl modified chitosan and butyl modified deacetylated chitosan, respectively.

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