A diffusion electrochemical reactor was proposed to remove elemental mercury (Hg-0) from coal-fired flue gas. The experiments were carried out in an undivided column reactor with a self-made gas diffusion electrode (GDE) as cathode and Ti/IrO2 as anode. Hg-0 was oxidized when the simulated gas passed through GDE. It turned out that the removal of Hg-0 in electrochemical process was dominated by electro-generated H2O2 and free radicals on GDE interface or in the electrolyte. Under 70 degrees C, Hg-0 removal efficiency exceeded 90% after 40 min electrolysis. The effects of operation parameters were investigated and the results demonstrated that voltage, gas flow rate, and initial concentration of Hg-0 had significant influences on Hg-0 removal, especially the reaction temperature, electrolyte concentration and pH. H2O2 and HO center dot in the electrolyte were measured by UV-vis spectrophotometer and electron spin resonance (ESR), respectively. The above results show that electrochemical technique is a promising method for emission control of Hg-0 from coal-fired flue gas. (C) 2016 Elsevier B.V. All rights reserved.