We present a numerical methodology to calculate electronic structures of a molecule in electrochemical environment. The methodology is based on the finite-temperature density functional theory (FTDFT) and allows us to study electronic properties of a molecule at a fixed chemical potential mu. The approach is applied to a reaction of NO+ + e(-) reversible arrow NO in chemical equilibrium. The solvent effect is taken into account by a conductor-like polarizable continuum model (C-PCM). We demonstrate that the method combined with C-PCM (FTDFT/C-PCM) successfully describes the electronic structures of the molecule in electrochemical environment. (c) 2007 Elsevier B.V. All rights reserved.