Fabrications of metal organic frameworks derived hierarchical porous carbon on carbon nanotubes as efficient bioanode catalysts of NAD⁺-dependent alcohol dehydrogenase

Herein, we developed an efficient anode catalyst for alcohol biofuel cell by integrating multi-walled carbon nanotubes (MWCNTs) into an isoreticular metal organic framework derived porous carbon. The derived porous carbon (PC) intercalated by MWCNTs (PC/MWCNTs) serviced as the anode component in catalyzing the electrooxidation of reduced β-Nicotinamide adenine dinucleotide (NADH), enabling catalysis to ethanol electrooxidation by alcohol dehydrogenase with NAD⁺ as both free coenzyme and electron transfer mediators (onset potential, 0.14 V vs. SCE, pH 8.0). Hierarchy of PC/MWCNTs with micro-, meso-, and macropores provides improved immobilization of electroactive enzymes, aids the facile transportations of electrolyte and increases the conductivity and specific surface areas of anode and results in a much higher catalytic current density for NADH (1.17 mA cm⁻² for 10 mM NADH, pH 9.0) and alcohol bioanode (maximum steady-state current density, 0.25 ± 0.03 mA cm⁻², pH 8.0) than its singular component analogues (PC and MWCNTs). The high Michaelis-Menten constant (166 ± 16.8 mM) favorites the detection of ethanol at high concentrations. The linear range of ethanol is 10–300 mM, with the sensitivity and detection limit as 24 nA mM⁻¹ and 3 mM. The study applies porous carbon nanomaterials as both electrocatalysts for coenzyme and scaffolds for enzymes, benefiting to feasible constructions of bioelectrodes with notable current densities.