Nanostructuring carbon supports for optimal electrode performance in biofuel cells and hybrid fuel cells

Abstract

The efficiencies of dioxygen reduction on common carbonaceous materials were compared using voltammetry and fuel cell measurements. Carbon paper (CP), carbon fibre (CF) or carbon cloth (CC) conducting supports were covered under water pump pressure with multiwalled carbon nanotubes (MWCNTs) to increase the working surface of the electrode, improve connectivity with enzyme molecules and provide direct electron transfer. Laccase was the biocathode catalyst catalyzing 4-electron reduction of oxygen to water on the nanostructured electrode. CP carbon paper was selected as the favourable electrode substrate, since it provided best durability holding firmly the carbon nanotubes together with the enzyme at the electrode surface. Zinc disc or fructose dehydrogenase was used as anode in the hybrid fuel cell and biofuel cell, respectively. The characteristics under externally applied resistances and potential-time dependencies under flowing solution conditions were evaluated. The hybrid fuel cell based on Zn anode and CP supported laccase cathode gave the best results in terms of power and open circuit potential (OCP). The full biofuel cell based on laccase and fructose dehydrogenase shows lower OCP but the power-time dependencies were similar to those of the hybrid biofuel cell. The nanostructured surfaces show good supercapacitor properties due to the presence of carbon nanotubes at the electrode surface. The fuel cells undergo self-charging/discharging and, therefore, can be conveniently employed in pulsed-work regime to power external devices.

Rapid and Oriented Immobilization of Laccases on Electrodes via a Methionine-Rich Peptide

“…Apart from supermolecules, organic solvents (e.g., ethanol, acetone, and acetonitrile) can influence the laccase conformation. Wu et al explained that organic solvent molecules have a role in surface wetting and protein denaturation. , In light of particular surface charge distributions of laccases, changing the electrode surface charges is another effective way to achieve favorable orientations and DET. , Besides, Mano’s group coupled the site-mutated cysteine of bilirubin oxidase (laccase homologue) to the electrode through maleimide chemistry and studied the effect of orientation on bioelectrocatalysis efficiency …”

Role of Organic Solvents in Immobilizing Fungus Laccase on Single-Walled Carbon Nanotubes for Improved Current Response in Direct Bioelectrocatalysis

“…Ever since the first DET example of laccase absorbed on a carbon black electrode reported in 1978, a main body of the efforts have focused on engineering the electrode-enzyme interface aimed at rational immobilization. These include physical adsorption on planar or nanostructred carbonaceous or gold electrodes, − conductive wiring by carbon nanotubes (CNTs), carbon or gold nanoparticles, − entrapment in polymers, liquid-crystal cubic phases, carbon microcrystals or aerogels, − covalent conjugation by cross-linkers, pyrene derivatives or self-assembled thiol monolayers, ,− supramolecular wiring by substrate-mimicking ligands, − and site-directed tethering by non-natural amino acids or affinity tags. , Another important aspect of improving DET calls for reduction of the protein backbone. For example, a part of the peptide chain hindering T1 copper can be genetically removed to increase DET rate with the truncated laccase .…”

“…Besides supramolecular aromatic wiring as mentioned above, enzyme inhibitors including organic solvents might help orientate laccase molecules on CNTs. So far, quite a number of CNT-based laccase electrodes featuring DET, especially those requiring Nafion entrapment, have been prepared from aqueous-nonaqueous mixtures, ,, and it was reported recently that laccase adsorbed from an ethanol-buffer solution onto MWCNT-covered carbon paste electrodes gave larger current densities . However, potential effects of organic solvents on laccase immobilization and subsequent bioelectrocatalytic performance have never been analyzed.…”

“…So far, quite a number of CNTbased laccase electrodes featuring DET, especially those requiring Nafion entrapment, have been prepared from aqueous-nonaqueous mixtures, 33,34,68 and it was reported recently that laccase adsorbed from an ethanol-buffer solution onto MWCNT-covered carbon paste electrodes gave larger current densities. 19 However, potential effects of organic solvents on laccase immobilization and subsequent bioelectrocatalytic performance have never been analyzed. Starting from this point, we embarked on the simple immobilization approach by adsorbing laccase onto SWCNTs with a moderate content of ethanol in buffered solution.…”

Power Generation by Selective Self-Assembly of Biocatalysts

“…The results indicate that self-assembly persisted even in the presence of pulp, enabling power generation and demonstrating the potential use of the methodology in complex environments. Evidently, compared to other, non-self-assembled, biofuel cells based on FDH//BOD (or laccase) DET assemblies, − the power output in our case is low, Table S1, Supporting Information. However, when normalizing the power output to the limiting biocatalyst loading, it seems that the price to be paid for the self-assembly and controlled disassembly features becomes insignificant, only about 10%.…”