Probing the nickel corrosion phenomena in alkaline electrolyte using tender x-ray ambient pressure x-ray photoelectron spectroscopy - IOPscience

ABSTRACT

Corrosion poses a significant challenge to many materials, from industrial structures to electrochemical catalysts. Nickel (Ni) is considered one of the most active metal catalysts for electrochemical water oxidation reaction in the alkaline environment. To gain more insight into corroded nickel electrodes in the water oxidation reaction, we employed operando ambient pressure x-ray photoelectron spectroscopy to detect the nickel/electrolyte interface under various potentials. To probe the influence of various halide anions on cycled Ni electrode/electrolyte interfaces undergoing the oxygen evolution reaction, we examined the surface changes in nickel electrodes after repeated electrochemical cycles in the presence of KOH mixed with KBr and KI under various potentials. As the applied potential became more anodic, we detected the formation of surface hydroxide and bromide when Br− was present in the electrolyte, whereas in I− -containing electrolytes, we found only hydroxides. The formation of oxidized Ni species was highly dependent on the type and concentration of halide ions. Br− facilitated the formation of more oxidized Ni species than I− did under the same concentration. In the presence of higher concentrations of potassium halide (100 mM) in the bulk electrolyte, metallic nickel could be completely oxidized at the most anodic potentials with surface hydroxide formation. This work reports the observation of cationic metal ions in the bulk electrolyte and describes in situ observation of degradation at the metal/electrolyte interface.