Hydrogenase-Coated Carbon Nanotubes for Efficient H₂ Oxidation

Abstract

Multiwalled carbon nanotubes grown on gold electrodes manufactured by microtechnology techniques have been used as a platform for oriented and stable immobilization of a Ni-Fe hydrogenase. Microscopic and electrochemical characterization of the system are presented. High-density currents due to H2 oxidation electrocatalysis, stable for over a month under continuous operational conditions, were measured. The functional properties of this nanostructured hydrogenase electrode are suitable for hydrogen biosensing and biofuel applications.

Biohydrogen for a New Generation of H2/O2 Biofuel Cells: A Sustainable Energy Perspective

“…Hases from various origins were also attached to CNTs. [194,197,198,230,231] Large increase in the catalytic current was observed, in addition to a better stability of the biocomposite, due to the covalent attachment of the enzyme on the CNT surface. Surfactants can be added to the CNT solution to achieve better dispersion, hence an increase in the available surface for enzyme loading.…”

“…It was demonstrated that H 2 oxidation switches from a direct to a mediated process according to the charge of the SAM. [162,193,194,198] Intriguingly, even with a monolayer of properly oriented Hase, no noncatalytic signals could be observed, precluding a calculation of catalytic turnover (only in the case of a [FeFe]-Hase did the coupling between electrochemistry on SAM electrodes and electrochemical scanning tunneling microscopy allow a turnover frequency of 21,000 s À1 for hydrogen production to be calculated). [199] No explanation can as yet be given for such a result.…”

“…The simplest way would be to avoid two different substrates, for example by the use of CNTs or CNFs directly grown on an electrode or through the use of carbon felts, which do not need further support. [194] Efforts to enhance the stability of the bioelectrodes have mainly focused on the interaction between the carbon host matrix and the enzymes. A covalent coupling between CNTs and the enzymes allowed for recovery of approximately 40 % of the power density after 24 h operation of the EBFCs.…”

Covalent Immobilization of Proteins on Carbon Nanotubes Using the Cross-Linker 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide—a Critical Assessment

“…Covalent attachment of proteins on carboxylated CNTs using the popular cross-linker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was first reported by Huang et al (12) and Jiang et al (13). Since then, it has been widely used in the covalent immobilization of proteins on carboxylated CNTs in biosensing studies (14)(15)(16)(17)(18)(19)(20)(21)(22).…”

Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies

“…Astier and co-workers reported that carbodiimide coupling of Alcaligenes faecalis copper nitrite reductase (CuNiR) to a carboxylate-terminated SAM electrode did not result in any catalytic response, whereas a noncatalytic peak sensitive to scan rate (k 0 ≈ 10 s -1 ) was observed. 216 De Lacey and coworkers achieved direct ET to immobilized DesulfoVibrio gigas NiFe hydrogenase by forming an amide bond between the glutamic residues surrounding the surface-exposed [4Fe4S] cluster of this enzyme (Figure 1) and either carbon electrodes 198 or carbon nanotubes 235 functionalized with amine groups. This immobilization was carried out at low pH and low ionic strength to take advantage of the enzyme's dipole moment and to encourage the adsorption of the enzyme in the orientation appropriate for fast electron transfer, i.e.…”