Analytical Techniques for Characterizing Enzymatic Biofuel Cells

Abstract

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

Recent advances in application of chitosan in fuel cells

“…Microorganisms are able to convert enormous amounts of energy from an incomparable range of chemical substrates [33]. Biofuel cells are a subset of fuel cells that employ biocatalysts such as a microbe, enzyme or even organelle interacting with an electrode surface [34,35].…”

“…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 [33]. Biofuel cells like other ones require porous anode and cathode structures that support fuel transport to the catalyst reaction sites [36].…”

“…The two main application areas that are being considered for enzymatic biofuel cells are in vivo, implantable power supplies for sensors and pacemakers and ex-vivo power supplies for small portable power devices (wireless sensor networks, portable electronics, etc.) [33].…”

Vertically Aligned Pd Nanowires for Glucose Oxidase Bioanode

“…Currently, there is a strong focus on the development of these biofuel cells for use as implantable and micro/ nano device power sources [2][3][4][5][6][7][8][9]. The desire to develop energy sources based on glucose biofuel cells for implantable devices can be attributed to the fact that the bioanode enzymes such as glucose oxidase and glucose dehydrogenase can oxidize glucose at physiological conditions.…”

“…Glucose oxidase was covalent immobilized using a hydrogel composite membrane onto the Pd nanowire arrays. Cyclic voltammetry measurements were performed at different scan rates and in different glucose concentration to evaluate the electrocatalytic activity of the hydrogel composite modified Pd nanowire arrays [2,19]. In principle, the combination of glucose oxidase and Pd nanowire arrays leads to the development of a glucose oxidase bioanode that can oxide glucose, enhance the bioanode conductivity and facilitate the direct electron transfer of the biocatalyst without the use of a mediator [8].…”