Electrochemical characterisation of multifunctional electrocatalytic mesoporous Ni-Pt thin films in alkaline and acidic media
Konrad Eiler, H. Krawiec, Iryna Kozina, Jordi Sort, Eva Pellicer
Abstract
Reliability and long-term performance are the key features of modern energy storage and conversion devices. The long-term stability depends entirely on the electrochemical and corrosion properties of device components. Single-phase mesoporous Ni-rich Ni-Pt thin films have shown to be a promising electrocatalyst for hydrogen evolution reaction (HER) and therefore with potential application in fuel cells, water electrolysers or similar devices. The HER activity of the mesoporous Ni-Pt films is reliable and stable in 0.5 M H2SO4 up to 200 linear sweep voltammetry cycles, however leaching of Ni occurs in absence of cathodic polarisation. Long-term electrolysis measurements at a HER current of –10 mA/cm2 reveal an increase in potential over time, which is minimised when the Pt content is increased. In 1 M NaOH, the material is stable up to an applied anodic limit of 1.5 V vs. Ag|AgCl although surface passivation takes place at 1.0 V. If the anodic limit does not exceed 0.6 V vs. Ag|AgCl, a fully reversible redox reaction is observed by cyclic voltammetry, with redox charges increasing with Pt content and scan speed. In addition, significantly higher current densities are recorded for mesoporous films compared to dense counterparts. This charge/discharge behaviour of the redox reaction indicates that the mesoporous Ni-Pt films may as well be used as an electrochemical supercapacitor. As a HER catalyst, the material is safely applicable in alkaline media.