Carbon nanofiber mesoporous films: efficient platforms for bio-hydrogen oxidation in biofuel cells

Abstract

The discovery of oxygen and carbon monoxide tolerant [NiFe] hydrogenases was the first necessary step toward the definition of a novel generation of hydrogen fed biofuel cells. The next important milestone is now to identify and overcome bottlenecks limiting the current densities, hence the power densities. In the present work we report for the first time a comprehensive study of herringbone carbon nanofiber mesoporous films as platforms for enhanced biooxidation of hydrogen. The 3D network allows mediatorless hydrogen oxidation by the membrane-bound hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. We investigate the key physico-chemical parameters that enhance the catalytic efficiency, including surface chemistry and hierarchical porosity of the biohybrid film. We also emphasize that the catalytic current is limited by mass transport inside the mesoporous carbon nanofiber film. Provided hydrogen is supplied inside the carbon film, the combination of the hierarchical porosity of the carbon nanofiber film with the hydrophobicity of the treated carbon material results in very high efficiency of the bioelectrode. By optimization of the whole procedure, current densities as high as 4.5 mA cm(-2) are reached with a turnover frequency of 48 s(-1). This current density is almost 100 times higher than when hydrogenase is simply adsorbed at a bare graphite electrode, and more than 5 times higher than the average of the previous reported current densities at carbon nanotube modified electrodes, suggesting that carbon nanofibers can be efficiently used in future sustainable H2/O2 biofuel cells.

Kinetic Analysis of Inactivation and Enzyme Reaction of Oxygen-Tolerant [NiFe]-Hydrogenase at Direct Electron-Transfer Bioanode

“…Similar phenomena were observed and studied with carbon nanotube (CNT) electrodes. 36 The v dependence of the wave at the KBGCE was very similar to that at Au electrodes (data not shown) except the fact that the decrease in the catalytic wave due to the inactivation at the KBGCEs is slow compared with that at the Au electrode.…”

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

“…De Poulpiquet et al used CNFs synthesized by CVD to entrap Aa MbH and Mv and Bp BODs. [42,237] Very high current densities were reached in the range of a few mA cm À2 in the absence of any covalent attachment. Graphene is a novel 2D layered material that presents excellent electronic, mechanical, and thermal stability, as well as large specific area.…”

“…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. [237,297] Entrapment of enzymes inside compacted mesoporous carbon led to stability of the bioelectrodes for operation for one week. [298] No covalent coupling was necessary in this case.…”

“…A) CNF deposit on a graphite electrode (from Ref. [237] with permission from the Royal Society of Chemistry). B) CNTs deposit on CFs (from Ref.…”

“…B) Membraneless EBFC using covalent attachment of enzymes on pyrene-functionalized CNTs that allows enhancement of the power density compared with a bare graphite electrode (adapted from Ref. [237] with permission from the Royal Society of Chemistry). C) Use of thermostable enzymes on CNFs allows the development of performant EBFCs (adapted from Ref.…”