Stability of Ni and Ti in Hydrogen Evolution in the Presence of 1-Butyl-3-methylimidazolium Tetrafluoroborate

摘要

Ni and Ti electrodes were tested for hydrogen evolution reaction in water electrolysis usingelectrolytes containing 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM橞F4) ionic liquid.Reductive currents of Ni and Ti at low potentials in BMIM橞F4 (12 wt%) and KOH (6 wt%) aqueouselectrolytes originate from hydrogen evolution with considering the electrolyte composition and theelectrochemical window of the ionic liquid, which was confirmed by Pt electrode. While the Tielectrode shows a similar hydrogen evolution activity to the Ni electrode in the BMIM橞F4 aqueouselectrolyte, its activity is inferior to the Ni electrode in the KOH aqueous electrolyte without the ionicliquid. The existence of the ionic liquid in aqueous electrolyte appears to change the hydrogenevolution kinetics at both Ni and Ti electrodes as seen in Tafel analysis. This is partly because+ BMIM橞F4 is susceptible to hydrolytic decomposition of BMIM owing to the hydrogen at C2 position- and of BF4 incurring HF formation. A measurement of electrode weight loss after a potentiostaticexperiment and an accompanying SEM analysis indicate the surface roughening of the electrodes andthe pore formation on the surface of Ti in the presence of BMIM橞F4. This change in surfacemorphology can be attributed to HF that could be formed from the hydrolytic instability of BMIM橞F4.