(577a) High-Rate NADH Electrocatalysis At Nanoscale Carbon Electrodes

Implementation of NADH-dependent enzymes in electrochemical bioreactors, biosensors, and biofuel cells is currently limited by poor kinetics of electrochemical NADH regeneration to form NAD⁺.  However, we have shown that high-rate NADH oxidation may be achieved by combining nanomaterials with deposited azines.  For example, high-rate electrodes may be fabricated by adsorbing methylene green on electroactivated carbon surfaces. A glassy carbon electrode was activated by cyclic voltammetry at 2.5 V to -1.5 V in phosphate buffer, leading to the formation of redox active quinones on the carbon surface. The electroactivated glassy carbon electrode possesses high capacitance and achieves NADH oxidation current density comparable to a 0.21 mg cm^-2 CNT electrode, a more than 200-fold increase compared to untreated glassy carbon. Deposition of methylene green (MG) on activated glassy carbon electrode and pretreated CNTs was successfully achieved by facile adsorption. The MG-CNT electrode demonstrates a nearly twofold increase compared to electropolymeried MG on CNT. We have shown that the electrogenerated NAD⁺ is nearly 100% bioactive, and have implemented this electrode in a bioreactor designed to oxidize glycerol to dihydroxyacetone.