Infrared Microscopy as a Probe of Composition within a Model Biofuel Cell Electrode Prepared from Trametes versicolor Laccase

Abstract

Infrared microscopy was applied in the study of laccase biofuel cell electrodes that demonstrated high current and power densities traceable to the use of a low equivalent weight (EW), short side chain (Aquivion) ionomer in the catalyst layer. The electrodes were prepared from a biocatalyst ink composed of orientation-directing anthracene-modified multi-walled carbon nanotubes (An-MWCNTs) in a dispersion of ionomer exchanged by hydrophobic cations. The ink was applied to an electronically conductive carbon felt support that was hot-pressed to a Nafion-NRE 212 (51 μm thickness) membrane, forming the framework for an air-breathing biofuel cell cathode. Infrared microscopy sampling was performed with the use of a microattenuated total reflection probe that enabled spectra to be recorded from~32 μm diameter circular spatial regions on the materials investigated. Sensitivity to deformation of the soft polymer membrane-based materials was assessed through trial experiments on pure membrane samples before approaching the compositionally more complex biofuel cell electrodes. In studies of laccase cathodes, infrared spectral features of enzyme, buffer anions and surrounding An-MWCNTs were identified. Heterogeneity in the spatial distribution of components and unexpected bands traceable to insoluble copper salts were detected. The results suggest directions for improving electrode activity and bring to light needs for advancing quantitative interpretations.

Functionalization of Carbon Nanotubes Surface by Aryl Groups: A Review

“…Bioelectrocatalysis plays an important role in modern chemistry [ 141 ]. The creation of electrodes with oriented immobilized enzymes is necessary for the development of biofuel cells [ 47 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 ], hybrid batteries [ 144 , 153 , 154 , 155 , 156 , 157 ], and biosensors [ 158 ]. CNTs are a promising basis for the creation of bioelectrodes due to their high electrical conductivity and surface area.…”

“…Further, each work uses enzymes isolated from their own type of microorganisms, which also makes it difficult to compare. However, anthracene arylated nanotubes are used most of all [ 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 155 , 156 , 158 , 160 , 161 , 166 ].…”

Redox-active Polymers in Biofuel Cells

“…It is important to understand the origin of losses in BFCs in order to extract design rules for next generation devices. Techniques such as infrared microscopy can be implemented to investigate the molecular composition within the localized regions of BFC electrodes 51 . An in-depth assessment of the structure and intermolecular…”

Functionalization of MWCNTs for Bioelectrocatalysis by Bacterial Two-Domain Laccase from Catenuloplanes japonicus

“…Carbon nanotubes allow the achievement of multifold expansion of the real electrochemically active surface and reduce amounts of catalysts used per unit area of oxygen electrode [6]. The possibility of surface functionalization of nanotubes by attaching the desired side groups like phenolic [7], aryl [8][9][10], and heterocyclic groups [11], allows for the immobilization of various catalysts [12,13].…”