Electrochemical hydrogen production from water electrolysis using ionic liquid as electrolytes: Towards the best device

Electrodes constructed with different electroactive materials such as platinum (Pt), nickel (Ni), 304 stainless steel (SS) and low carbon steel (LCS) have been tested in water electrolysis using 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4). All experiments were performed at room temperature using a classical Hoffman's cell operating at atmospheric pressure and at different cathodic potentials. For the electrodes studied herein, in the presence of a 10 vol.% solution of BMI.BF4 in water, current densities (j) in the range 10–42 mA cm−2 were observed, with overall hydrogen production efficiencies (experimental/theoretical hydrogen production ratio) between 82 and 98%. The highest j values obtained with Pt, Ni, SS and LCS electrodes were 30, 12, 10 and 42 mA cm−2, respectively, and all efficiencies were in the 85–99% range. These comparative results show that the LCS electrocatalyst constitutes an attractive alternative for the technological production of high purity hydrogen by water electrolysis reaction since the LCS electrode gave j and efficiencies as high as those observed with platinum electrodes.