Biofuel Cell Anodes Integrating NAD⁺-Dependent Enzymes and Multiwalled Carbon Nanotube Papers

This research aims to overcome kinetics, ohmic and mass transport limitations by improving the nanoarchitectured design of the catalytic layer and the mass transport system in order to improve the current output and stability of the bioanode. Carbon nanostructured material, the multiwalled carbon nanotube (MWNTs) paper (buckeye paper (BEP)), and the polymeric structure of chitosan-carbon nanotubes (CNTs) mixture are integrated in the design. Integration of these nanostructured materials with various enzymes-alcohol, lactate and glucose dehydrogenases (ADH, LDH and GDH respectively)-was performed and analyzed. Polymethylene green (PMG) is used as a catalyst toward the oxidation of NADH to NAD+. The GDH-based anodic interface showed the best performance in the static electrolytic cell as well as in the quasi-2D flow-fan cell. Michaelis-Menten analysis on the GDH-based bioanode showed an IMax = 3.382 ± 0.180 mA.cm−2 and KM = 17.5 ± 3.1 mM compared to IMax = 226.6 ± 10.1 μA.cm−2 and KM = 16.0 ± 2.5 mM for ADH and, IMax = 53.4 ± 5.1 μA.cm−2 and KM = 6.6 ± 3.3 mM for LDH respectively (electrolytic cell). Stability studies showed the GDH- bioanode conserved ∼80% of its initial performance at 15 days and ∼65% at 30 days of dry storage at 4°C.