The regeneration of enzymatically-active reduced form of enzymatic cofactor nicotinamide adenine dinucleotide (1,4-NADH) from the oxidized form (NAD(+)) in a batch electrochemical reactor employing bare (non-modified) metal electrodes was investigated as a function of electrode potential and electrode material (Ti, Ni, Co and Cd). It was found that the regeneration of 1,4-NADH employing the electrodes is feasible; all the electrodes were capable of producing more than an 80% enzymatically-active product (1,4-NADH), reaching a 96% product purity on Ti. The product purity was found to be highly potential-, and material dependant. The origin of the material/potential dependency was related to the strength of the metal-hydrogen (M-H-ads) bond, and thus to the potential dependence of the Had, electrode surface coverage. In contradiction to literature, bare (non-modified) metal electrodes were found to be good candidates for electrochemical regeneration of enzymatically-active 1,4-NADH, when the regeneration is performed at a specific overpotential. (C) 2014 Elsevier B.V. All rights reserved.