Performance Of Enzymatic Biofuel Cell Research Articles

Bimetallic Electrocatalyst of Hyaluronate-Au@Pt for Durable Oxygen Reduction in Biofuel Cells

Biofuel cells (BFCs) have attracted great attention as battery substitutes in wearable and implantable devices. Oxygen reduction enzymes such as bilirubin oxidase, laccase, and peroxidase are used as cathodic materials in enzymatic BFCs (EBFCs). However, the low power output and short lifetime of EBFCs have limited their further commercial applications. Here, a bimetallic electrocatalyst of hyaluronate-Au@Pt (HA-Au@Pt) was synthesized to enhance the oxygen reduction reaction (ORR) performance of EBFCs by modifying the electronic structure of Pt with high oxygen reduction. HA is a biocompatible, hydrophilic, and linear polysaccharide, which can be utilized as a binder and stabilizer to enhance the dispersibility, stability, and biocompatibility of Au@Pt for wearable and implantable devices. The open circuit voltage is 0.35 V and the maximum current density is −166 μA/cm2 at −0.04 V for the optimized HA-Au@Pt electrocatalyst with 0.5 mM H2PtCl6. In comparison with other biocompatible polymers, HA in HA-Au@Pt catalysts showed excellent dispersibility and remarkable durability under the ORR condition. The power density of a glucose oxidase-based EBFC appeared to be 15.8 μW/cm2 at 0.29 V, demonstrating the feasibility of HA-Au@Pt as a promising electrocatalyst in the energy generation of EBFCs.

Direct Energy Conversion from <i>Metroxylon sagu</i> via Multienzyme Catalysis in Enzymatic Biofuel Cell

Biomass substrates have been used extensively in the production of biofuel by the simultaneous saccharification and fermentation (SSF) method. Biomass sources from the plant are preferable to produce biofuel because of the high sugar content. Adapting the SSF method, this work reported on the direct energy conversion from Metroxylon sagu via multienzyme catalysis in an enzymatic biofuel cell (EBFC). Metroxylon sagu locally called Sago is an industrial crop mainly found in Mukah, Sarawak. Sago is a type of starch that consists mainly of amylose and amylopectin structures. In this study, the polysaccharides are converted to glucose using alpha-amylase (α-amylase) and glucoamylase (GAmy) enzymes. The factors influencing the multienzyme catalysis, such as the substrate concentration, enzymes loading, pH and time, were varied to obtain the optimized condition for glucose production. The results of the glucose content using a microplate reader indicate that glucose was successfully produced via multienzyme catalysis. The oxidation of glucose employed in the EBFC was confirmed by the cyclic voltammogram (CV) analysis. The performance of EBFC was also assessed based on its maximum power density (MPD) and open circuit voltage (OCV) values. This multienzyme catalysis simplifies the multi-step process involved in converting polysaccharides to glucose.

Maximizing the enzyme immobilization of enzymatic glucose biofuel cells through hierarchically structured reduced graphene oxide

The number of immobilized glucose oxidase (GOx) molecules is considerably increased by the structural modification of reduced graphene oxide (rGO), and the performance of enzymatic biofuel cells (EBFCs) is positively affected by the modification process. To do this, new rGO with three-dimensional open porous structure is formed by spray freeze drying method (sprGO), while tetrathiafulvalene (TTF) as mediator, and GOx are sequentially immobilized onto sprGO. To improve the loading amount of catalyst, rGO structure is modified to open porous sprGO structure possessing numerous anchoring sites, after which gelatin film crosslinked by glutaraldehyde is fabricated onto sprGO to prevent any losses of other components (sprGO/[TTF-GOx]/crosslinked-gelatin). Specific surface area and charge transfer resistance of sprGO are quantitatively measured, and the actual amount of immobilized GOx and the performance of EBFC using this catalyst are electrochemically examined. With this, it is found that the amount of GOx immobilized in sprGO/[TTF-GOx]/crosslinked-gelatin is twice better that in rGO/[TTF-GOx]/crosslinked-gelatin. More specifically, EBFC using this catalyst shows open circuit voltage of 0.85 V and maximum power density of 380 μW/cm2, and this is 1.4 times better than that using rGO/[TTF-GOx]/crosslinked-gelatin. These results indicate that the amount of immobilized GOx strongly affects the performance capabilities of EBFCs.

New Biocatalyst Including a 4-Nitrobenzoic Acid Mediator Embedded by the Cross-Linking of Chitosan and Genipin and Its Use in an Energy Device.

A new anodic catalyst consisting of carbon nanotube, 4-nitrobenzoic acid, chitosan, genipin, and glucose oxidase (GOx) (CNT/4-NBA/[Chit/GOx/GP]) is suggested to promote the glucose oxidation reaction (GOR) and the performance of enzymatic biofuel cell (EBC). In this catalyst, through the cross-linked structure of chitosan and genipin and the proper distribution of amine groups within chitosan, many GOx molecules are maximally captured, their leaching out is suppressed, and the GOR is improved upon. In addition, 4-nitrobenzoic acid plays the role of mediator well. The effect induced by the cross-linked structure is evaluated by ultraviolet-visible (UV-vis) spectroscopy, pH measurements, and electrochemical characterizations. According to the characterizations, the new CNT/4-NBA/[Chit/GOx/GP] catalyst contains a large amount of GOx (17.8 mg/mL) and produces a high anodic current (331 μA/cm2 at 0.3 V vs Ag/AgCl) with a low onset potential (0.05 V vs Ag/AgCl) because its catalytic activity follows the desirable reaction pathway that minimizes creation of a protonated amine group that interferes with GOR. When the performance of EBC using this catalyst as an anodic electrode is measured, the EBC shows a high open-circuit voltage of 0.54 V and a maximum power density of 38 μW/cm2.

Membraneless biofuel cells using new cathodic catalyst including hemin bonded with amine functionalized carbon nanotube and glucose oxidase sandwiched by poly(dimethyl-diallylammonium chloride)

A new cathodic catalyst is developed for improving the performance of membraneless enzymatic biofuel cell (EBC) by enhancing overall oxygen reduction reaction (ORR). In this catalyst, both hemin and glucose oxidase (GOx) are considered as enzymatic catalysts to facilitate H2O2 reduction reaction (HRR) and partial oxygen reduction reaction (PORR), respectively. Hemin is attached to amine group functionalized carbon nanotube (Amine-CNT) to form amide bond, and GOx is conjugated with two poly(dimethyl-diallylammonium chloride) (PDDA) layers to form sandwich-like structure. As a result, [Amine-CNT/Hemin]/PDDA/GOx/PDDA catalyst is completed. This catalyst plays a role in reducing the amount of GOx leached out and preserving the mass transfer of fuels, and finally, increasing the catalytic activity for cathodic reactions. According to electrochemical estimation, its onset potential reaches 0.4V vs. Ag/AgCl and current density significantly increases to 323μAcm−2. When the performance of membraneless EBC adopting this catalyst is measured, maximum power density is 24.1±0.61μWcm−2 and its activity preserves 82.1% after four weeks. This excellent result is because PORR and HRR are promoted by the rigid connection of GOx and hemin, which is mainly induced by the sandwich effect of GOx by PDDA layers.

Dual catalytic functions of biomimetic, atomically dispersed iron-nitrogen doped carbon catalysts for efficient enzymatic biofuel cells

We report that the performance of enzymatic biofuel cell (EBC) can be boosted by exploiting the dual function of iron- and nitrogen-codoped carbon nanotube (Fe–N/CNT) catalysts. The Fe–N/CNT is directly used as a cathode catalyst for oxygen reduction reaction while it is combined with glucose oxidase (GOx) and polyethylenimine (PEI) to form GOx/PEI/[Fe–N/CNT] for catalyzing the overall oxidation reactions including glucose oxidation reaction at the anode. The cathode employing Fe–N/CNT catalyst shows excellent onset potential and current density (0.29 V and of 0.9 mA cm−2). In anode, GOx/PEI/[Fe–N/CNT] shows proper onset potential and current density (0.17 V and 74.3 μA cm−2) with the injection of 8 mM glucose solution. More quantitatively, its Michaelis-Menten constant and maximum current density are 139.4 mM and 347.1 μA cm−2, respectively, and its catalytic activity is well maintained preserving 81.2% of its initial value even after four weeks. The EBC comprising Fe–N/CNT at the cathode and GOx/PEI/[Fe–N/CNT] at the anode exhibits the maximum power density (MPD) of 63 μW cm−2. This is the first report that demonstrates the possibility of the heme mimicking nanocatalyst as both anodic and cathodic catalysts for EBCs.

On-Chip Enzymatic Microbiofuel Cell-Powered Integrated Circuits

In situ energy harvesting is a major limitation for the development of implantable biomedical digital devices. Considerable efforts have been made to improve Glucose/O2 Enzymatic Biofuel Cells (EBFCs), able to generate electrical power in the physiological environment, in order to match the demands of biomedical electronics [1]. A key advance was the development of redox hydrogels. They permit efficient connection of high amounts of oxidoreductases to electrodes, leading to easily miniaturizable BFCs with power densities in the range of 100 μW.cm-2 suitable for application [2]. However, their open circuit potentials still fall below the requirements of conventional electronics. On the other hand, the power and voltage demands have decreased thanks to tremendous progress in low-power electronics [3], rendering devices compatible with the performance of EBFCs. Here we demonstrate that common data processing functions such as binary counting can be powered by a glucose/O2 micro-EBFC directly integrated on an Application Specific Integrated Circuit (ASIC) at the die level. An EBFC based on Glucose Oxidase and Bilirubin Oxidase hydrogels immobilized on 400 μm diameter electrodes was designed on the Si chip of the 4-bit ripple-counter. The system could be continuously powered during several hours from a single 50 μL droplet of aerated 5mM glucose solution. 1] S. Cosnier, A. Le Goff, M. Holzinger, Electrochem. Comm., 2014, 38, 19-23. [2] N. Mano, F. Mao, A. Heller, JACS, 2003, 125, 6588-6594. [3] A. Chandrakasan, N. Verma, D.C. Daly, Annual Rev. Biomed. Eng., 2008, 10, 247-274.

Nitrogen-doped graphene approach to enhance the performance of a membraneless enzymatic biofuel cell

Heteroatom-doping of pristine graphene is an effective route for tailoring new characteristics in terms of catalytic performance which opens up potentials for new applications in energy conversion and storage devices. Nitrogen-doped graphene (N-graphene), for instance, has shown excellent performance in many electrochemical systems involving oxygen reduction reaction (ORR), and more recently glucose oxidation. Owing to the excellent H2O2 sensitivity of N-graphene, the development of highly sensitive and fast-response enzymatic biosensors is made possible. However, a question that needs to be addressed is whether or not improving the anodic response to glucose detection leads to a higher overall performance of enzymatic biofuel cell (eBFC). Thus, here we first synthesized N-graphene via a catalyst-free single-step thermal process, and made use of it as the biocatalyst support in a membraneless eBFC to identify its role in altering the performance characteristics. Our findings demonstrate that the electron accepting nitrogen sites in the graphene structure enhances the electron transfer efficiency between the mediator (redox polymer), redox active site of the enzymes, and electrode surface. Moreover, the best performance in terms of power output and current density of eBFCs was observed when the bioanode was modified with highly doped N-graphene.

Cathodic biocatalyst consisting of laccase and gold nanoparticle for improving oxygen reduction reaction rate and enzymatic biofuel cell performance

New catalyst for promoting oxygen reduction reaction (ORR) and enzymatic biofuel cell (EBC) performance is suggested. The catalyst consist of laccase (LAC) and gold nanoparticle (GNP)-naphthalenethiol (NPT), which are linked to polyethyleneimine (PEI) and carbon nanotube (CNT) (CNT/PEI/[GNP-NPT]/LAC). Its onset potential and ORR rate are improved due to adoptions of PEI and GNP-NPT. Namely, CNT/PEI induces more immobilization of LACs and GNP-NPT acts as electron relay between CNP and NPT by thiol-gold bond and between CNT/PEI and LACs by electron collection effect. Even in EBC measurement, maximum power density of EBC using CNT/PEI/[GNP-NPT]/LAC is highest as 13μWcm−2.

A hybrid biocatalyst consisting of silver nanoparticle and naphthalenethiol self-assembled monolayer prepared for anchoring glucose oxidase and its use for an enzymatic biofuel cell

A novel hybrid biocatalyst is synthesized by the enzyme composite consisting of silver nanoparticle (AgNP), naphthalene-thiol based couplers (Naph-SH) and glucose oxidase (GOx), which is then bonded with the supporter consisting of polyethyleneimine (PEI) and carbon nanotube (CNT) (CNT/PEI/AgNPs/Naph-SH/GOx) to facilitate glucose oxidation reaction (GOR). Here, the AgNPs play a role in obstructing denaturation of the GOx molecules from the supporter because of Ag-thiol bond, while the PEIs have the AgNPs keep their states without getting ionized by hydrogen peroxide produced during anodic reaction. The Naph-SHs also prevent ionization of the AgNP by forming self-assembled monolayer on their surface. Such roles of each component enable the catalyst to form (i) hydrophobic interaction between the GOx molecules and supporter and (ii) π-conjugated electron pathway between the GOx molecules and AgNP, promoting electron transfer. Catalytic nature of the catalyst is characterized by measuring catalytic activity and performance of enzymatic biofuel cell (EBC) using the catalyst. Regarding the catalytic activity, the catalyst leads to high electron transfer rate constant (9.6±0.4s−1), low Michaelis-Menten constant (0.51±0.04mM), and low charge transfer resistance (7.3Ωcm2) and high amount of immobilized GOx (54.6%), while regarding the EBC performance, high maximum power density (1.46±0.07mWcm−2) with superior long-term stability result are observed.

A new biocatalyst employing pyrenecarboxaldehyde as an anodic catalyst for enhancing the performance and stability of an enzymatic biofuel cell

A new enzyme catalyst consisting of pyrenecarboxaldehyde (PCA) and glucose oxidase (GOx) immobilized on polyethyleneimine (PEI) and a carbon nanotube supporter (CNT/PEI/[PCA/GOx]) is suggested, and the performance and stability of an enzymatic biofuel cell (EBC) using the new catalyst are evaluated. Using PCA, the amount of immobilized GOx increases (3.3 U mg−1) and the electron transfer rate constant of the CNT/PEI/[PCA/GOx] is promoted (11.51 s−1). Also, the catalyst induces excellent EBC performance (maximum power density (MPD) of 2.1 mW cm−2), long-lasting stability (maintenance of 93% of the initial MPD after 4 weeks) and superior catalytic activity (flavin adenine dinucleotide redox reaction rate of 0.62 mA cm−2 and Michaelis–Menten constant of 0.99 mM). These characteristics are ascribed to effects of (i) electron collection due to hydrophobic interactions, (ii) electron transfer pathways due to π-conjugated bonds and (iii) enzyme stabilization due to π-hydrogen bonds that are newly induced by the PCA/GOx composite. The existence of such positive interactions is properly verified using X-ray photoelectron spectroscopy and enzyme activity measurements.

Mathematical modeling of nonlinear reaction–diffusion processes in enzymatic biofuel cells

Enzymatic biofuel cells convert the chemical energy of biofuels into electrical energy by employing oxidoreductase enzymes as catalysts. They have attracted considerable attention due to their potential use as a promising alternative to traditional power sources. Also, enzyme-modified electrodes have important applications in electrochemical biosensors, bioreactors, implantable medical devices as well as in biochemistry as a source of information on the action of enzymes. Among the different electrochemical techniques available, enzymatic biofuel cells and electrodes are generally studied via cyclic voltammetry, chronoamperometry, polarization curves and impedance measurements to gain better insight into the enzymatic system. The main aim is to assess the influence of the mediator species and its diffusivity, the loading of biocatalysts, the amount of substrates, mediators and inhibitors, the strategy of enzyme immobilization, etc. as well as to study the enzymatic kinetic mechanism. Within this context, mathematical models must be used to understand, predict and optimize the performance of enzymatic biofuel cells and electrodes as a function of the chief experimental parameters above mentioned. In this review article, major recent research activity concerning the mathematical modeling of enzymatic electrodes and fuel cells is discussed, highlighting the main contributions as well as current problems and challenges.

Amide group anchored glucose oxidase based anodic catalysts for high performance enzymatic biofuel cell

Abstract A new enzyme catalyst is formed by fabricating gold nano particle (GNP)-glucose oxidase (GOx) clusters that are then attached to polyethyleneimine (PEI) and carbon nanotube (CNT) with cross-linkable terephthalaldehyde (TPA) (TPA/[CNT/PEI/GOx-GNP]). Especially, amide bonds belonging to TPA play an anchor role for incorporating rigid bonding among GNP, GOx and CNT/PEI, while middle size GNP is well bonded with thiol group of GOx to form strong GNP-GOx cluster. Those bonds are identified by chemical and electrochemical characterizations like XPS and cyclic voltammogram. The anchording effect of amide bonds induces fast electron transfer and strong chemical bonding, resulting in enhancements in (i) catalytic activity, (ii) amount of immobilized GOx and (ii) performance of enzymatic biofuel cell (EBC) including the catalyst. Regarding the catalytic activity, the TPA/[CNT/PEI/GOx-GNP] produces high electron transfer rate constant (6 s−1), high glucose sensitivity (68 μA mM−1 cm−2), high maximum current density (113 μA cm−2), low charge transfer resistance (17.0 Ω cm2) and long-lasting durability while its chemical structure is characterized by XPS confirming large portion of amide bond. In EBC measurement, it has high maximum power density (0.94 mW cm−2) compatible with catalytic acitivity measurements.

Development of biofuel cell adopting multiple poly(diallyldimethylammonium chloride) layers immobilized on carbon nanotube as powerful catalyst

A new enzymatic biofuel cell (EBC) adopting multiple glucose oxidase (GOx) and poly(diallyldimethylammonium chloride) (PDDA) immobilized on carbon nanotube (CNT) ([GOx/PDDA]n/CNT) is fabricated and effects of [GOx/PDDA]n/CNT catalysts on EBC performance are investigated using various electrochemical characterizations. Initially, both redox reaction of flavin adenine dinucleotides (FADs) within GOx and stepwise deposition of PDDA and GOx on CNT are estimated to determine optimal [GOx/PDDA]n/CNT catalyst. Also, its electron transfer pathway and reaction mechanism related to oxygen mediator is elucidated. With the optimized [GOx/PDDA]5/CNT catalyst, excellent catalytic activity and EBC performance are measured. When the catalyst is used, its electron transfer rate constant is 15.97 s−1, glucose sensitivity is 17 μA mM−1 cm−2, Michaelis–Menten constant is 1.44 mM and EBC maximum power density (MPD) is 0.79 mW cm−2. It indicates that the values are better than those of other similar structures. Moreover, in a comparison with MPDs of EBCs without provision of glucose, it is proved that PDDA and GOx make key role in improving EBC performance.

Development of a glucose oxidase-based biocatalyst adopting both physical entrapment and crosslinking, and its use in biofuel cells.

New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL(-1), they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL(-1) GOx displays a high electron transfer rate, followed by excellent catalytic activity and EBC performance.

Effects of multiple polyaniline layers immobilized on carbon nanotube and glutaraldehyde on performance and stability of biofuel cell

Enzymatic biofuel cell (EBC) employing new catalyst for anode electrode is fabricated. The new catalyst consists of glucose oxidase (GOx), polyaniline (PANI) and carbon nanotube (CNT) that are multiply stacked together and finally the stack layer is surrounded by glutaraldehyde (GA) (GA/[GOx/PANI/CNT]n). To evaluate how the GA/[GOx/PANI/CNT]n layer affects EBC performance and stability, electrochemical characterizations are implemented. Regarding optimization, GA/[GOx/PANI/CNT]3 is determined. For elucidating reaction mechanism between glucose and flavin adenine dinucleotide (FAD) of GA/[GOx/PANI/CNT]3, associated investigations are performed. In the evaluations, drop in reduction current peak of FAD is observed with provisions of glucose and O2, while glucose does not influence FAD reaction without O2, confirming O2 makes mediator role. When the GA/[GOx/PANI/CNT]3 layer is adopted, superior catalytic activity and EBC performance are gained (electron transfer rate constant of 5.1s−1, glucose sensitivity of 150ìAmM−1cm−2, and EBC maximum power density (MPD) of 0.29mWcm−2). Regarding EBC stability, MPD of EBC adopting GA/[GOx/PANI/CNT]3 maintains up to 93% of their initial value even after four weeks. Although GA is little effective for improving EBC performance, EBC stability is helped by GA due to its adhesion promotion capability with [GOx/PANI/CNT]n layer.

(Invited) Bioelectrocatalytic Oxidation of Sucrose with an Enzyme Cascade Assembled on a DNA Scaffold

Over the last decade, there has been substantial research focused on multi-enzyme cascades as anodic catalysts to improve the performance of enzymatic biofuel cells, as it allows for the conversion of more chemical energy stored in complex fuels. However, the performance of these enzyme systems is often limited by the mass transport of intermediate substrates between enzymes. Nature addresses this issue by organizing metabolic enzymes in a sequential and proximal manner to enhance the efficiency of metabolic pathways. In this work, we investigate the utilization of DNA as a structural scaffold for the assembly of the invertase/glucose oxidase enzymatic supercomplex to improve sucrose bioelectrocatalytic activity. It has been found that the DNA-assembled enzyme cascade has higher activity than the free cascade, both in solution and in the immobilized state on a bioanode surface. The organization of the enzyme cascade on the DNA scaffold leads to a 100% increase in the current density in amperometric measurements for a sucrose biosensor and a 75% increase in the power density of the biofuel cell. This is the first evidence of the advantages of utilizing DNA scaffords for improved bioelectrocatalysis.

Fabrication of biofuel cell containing enzyme catalyst immobilized by layer-by-layer method

Enzymatic biofuel cell (EBC) employing a layer-by-layer (LbL) structure consisting of multiple layers of glucose oxidase (GOx) and poly(ethyleneimine) (PEI) at carbon nanotube (CNT) ([GOx/PEI]n/CNT) is fabricated. The [GOx/PEI]n/CNT serves as anode catalyst for promoting glucose reaction, while Pt is employed as cathode catalyst. To evaluate effect of [GOx/PEI]n/CNT on EBC performance and stability, several characterizations are conducted. The optimal GOx/PEI layer is determined electrochemically, and it turns out that [GOx/PEI]2/CNT is the best. Electron transfer rate constant of the optimal layer is 11.3s−1, its glucose sensitivity is 83 μAmM−1cm−2, and maximum power density of EBC adopting [GOx/PEI]2/CNT is 1.34 mWcm−2. The values are superior to those of other reference structures, indicating that the [GOx/PEI]2/CNT can produce excellent reactivity, followed by improved EBC performance. In terms of redox reaction mechanism of flavin adenine dinucleotide (FAD) within [GOx/PEI]2/CNT, glucose does not affect the redox reaction of FAD, while oxygen serves as mediator in transferring electrons and protons produced by glucose oxidation into those for reduction reaction of FAD. It is also found that the [GOx/PEI]2/CNT is confined by surface reaction and the reaction is quasi-reversible. Regarding long-term stability, [GOx/PEI]2/CNT maintains ∼83% of initial activity even after two weeks.

Improved Bioelectrocatalytic Oxidation of Sucrose in a Biofuel Cell with an Enzyme Cascade Assembled on a DNA Scaffold

The employment of multi-enzyme cascades as catalysts is a promising strategy to improve performance of enzymatic biofuel cells, as it allows for the conversion of more chemical energy stored in complex fuels. However, the performance of these enzyme systems is often limited by the mass transport of intermediate substrates between enzymes. Nature addresses this issue by organizing metabolic enzymes in a sequential and proximal manner to enhance the efficiency of metabolic pathways. In this work, we investigate the utilization of DNA as a structural scaffold for assembly of the invertase/glucose oxidase enzyme cascade to improve sucrose bioelectrocatalytic activity. It has been found that the DNA-assembled enzyme cascade has higher activity than the free cascade, both in solution and in the immobilized state on an electrode surface. The organization of the enzyme cascade on the DNA scaffold leads to a 100% increase in the current density in amperometric measurements and a 75% increase in the power density of the biofuel cell. This is the first evidence of the advantages of utilizing DNA scaffords for improved bioelectrocatalysis.

Highly ordered tailored three-dimensional hierarchical nano/microporous gold–carbon architectures

The preparation and characterization of three-dimensional hierarchical architectures, consisting of monolithic nanoporous gold or silver films formed on highly ordered 3D microporous carbon supports, are described. The formation of these nano/microporous structures involves the electrodeposition or sputtering of metal alloys onto the lithographically patterned multi-layered microporous carbon, followed by preferential chemical dealloying of the less noble component. The resulting hierarchical structure displays a highly developed 3D interconnected network of micropores with a nanoporous metal coating. Tailoring the nanoporosity of the metal films and the diameter of the large micropores has been accomplished by systematically changing the alloy compositions via control of the deposition potential, plating solution and coarsening time. SEM imaging illustrates the formation of unique biomimetic nanocoral- or nanocauliflower-like self-supporting structures, depending on the specific preparation conditions. The new 3D hierarchical nano/microporous architectures allow for enhanced mass transport and catalytic activity compared to common nanoporous films prepared on planar substrates. The functionality of this new carbon–gold hierarchical structure is illustrated for the greatly enhanced performance of enzymatic biofuel cells where a substantially higher power output is observed compared to the bare microporous carbon substrate.