Abstract Scope |
We investigate the formation of surface phases on nickel (Ni) during cathodic charging in 1M H2SO4 solution. We characterize these new phases using a wide range of characterization techniques, including XRD, EBSD, Kelvin Probe Force Microscopy (KPFM), EDS, and SIMS. We confirmed that these phases are complexes that rich in Ni, O, H and S, but free of C. In steady-state, the phases have distinct crystal structures, and are aggregated into surface filamentary shape with a thickness of ~200nm and covered approximately 30% of the Ni surface. They appear to be thermodynamically stable in air but are also easily removed by ultrasonication. Most importantly, the surface electrochemical potentials of these phases are cathodic with respect to the surrounding Ni surface by ~120mV. These findings stand to advance understanding of the catalytic activity of Ni cathodes, H uptake and embrittlement in Ni, and the onset of localized corrosion during cathodic charging. |