An air-stable dinuclear iron-dithiolene complex with an Fe-2(mu-S)(2) core, [Fe-III(mnt)(2)](2)(2-) (mnt = maleonitriledithiolate), has been found to serve as an electrode catalyst toward the reduction of water into molecular hydrogen with an overpotential of 560 mV. The acid form of a buffer reagent, such as CH3CO2H, has been found to serve as a major proton mediator during the electrocatalytic tic hydrogen evolution.