Improvement of Electrochemical Performance of Bilirubin Oxidase Modified Gas Diffusion Biocathode by Hydrophilic Binder

Abstract

Performance of bilirubin oxidase (BOD) modified gas diffusion biocathode has been highly improved by incorporating a hydrophilic polymer as binder to form effective Ketjen black (KB)-immobilized structure for the enzyme reaction on carbon paper electrode. An aqueous dispersion of styrene-butadiene rubber latex with sodium carboxymethylcellulose (SBR/CMC) was employed as hydrophilic binder. In direct electron transfer system, the biocathode with SBR/CMC binder exhibited larger O2 reduction current in phosphate buffer solution (PBS, pH 7.0) at room temperature, compared with that of a poly(vinylidine fluoride) binder electrode, which is a typical hydrophobic polymer. Performance of the biocathode was further improved by utilizing mediator electron transfer system, and the maximum current density of ∼27 mA cm−2 was achieved in pH 5.0 PBS. These improvements are believed to be due to hydrophilic property of the KB-immobilized electrode surface by the SBR/CMC binder, leading to high-dispersion of BOD on the surface and also stable interface formation of O2 gas / enzyme / electrolyte during the reaction. Furthermore, we fabricated a glucose/O2 cell composed of the biocathode and an opposite bioanode with glucose oxidase. The full-cell successfully achieved mW-class power density of 5.22 mW cm−2 with an open-circuit voltage of 0.61 V in pH 7.0 PBS.

O2Reduction in Enzymatic Biofuel Cells

“…However, designing a gas-diffusion cathode is not trivial. The gas-diffusion cathode usually consists of two layers: a gas-diffusion layer made of hydrophobized carbon black , or Ketjen black, ,, which has to be permeable to gas; a hydrophilic catalytic layer made with carbon black, carbon cloth, CNTs, − or carbon felt and containing the MCO. These first two layers may also be added on top of a third layer providing for mechanical stability.…”

Multi‐Enzyme Immobilized Anodes Utilizing Maltose Fuel for Biofuel Cell Applications

“…The EFCs consisted of CF‐based multi‐enzyme bioanodes and a KB/BOD/ABTS/CP based biocathode without any separators between them. The biocathode was designed and prepared to provide enough current for the biocathode not to control the EFC output, as shown in Figure S6 . Figure a shows the configuration of our EFC used in this study which is a normal block form one made of acrylic resin.…”

“…The biocathodes for O 2 reduction were fabricated according to our previous paper . They employed CP of 0.35 mm thick as the electrode base which was hydrophilized by treating with an ozonizer (UV/Ozone Processing Unit, SSP16‐110 set, SEN LIGHTS Corporation, Japan) prior to catalyst‐loading as follows.…”

“…We conducted electrochemical measurements of the biofuel cells in the voltage range from open‐circuit voltage to 0 V at room temperature under quiescent conditions to obtain voltage vs. current or power plots by applying constant voltage for 2 min. The cathode is a gas diffusion type electrode supplied with pure oxygen gas and tested as described in our previous report …”

Surfactant-Free Formate/O2 Biofuel Cell with Electropolymerized Phenothiazine Derivative-Modified Enzymatic Bioanode

“…Carbon materials are widely used in enzymatic biofuel cells to increase the enzyme modification density. ,− In particular, carbon nanotubes (CNTs) enjoy high popularity due to their high specific surface area and electrical conductivity. ,,,− The high propensity of CNTs for agglomeration is typically mitigated through the addition of surfactants to disperse CNT for drop-coat process. ,,,, However, they inevitably dissolve from the CNT electrode into the electrolyte and thus hydrophilize an opposite gas-diffusion biocathode to cause electrolyte leakage and/or reduce fuel-cell performance due to electrolyte flooding and the loss of oxygen supply to the biocathode . Therefore, the preparation of surfactant-free bioanodes is essential for the realization of high-performance formate/O 2 biofuel cells.…”