Electrochemical and corrosion behaviour of novel Zr-Ni(Co,Fe)-Al metallic glasses as precursors of nanostructured cathodes for water splitting

The present study demonstrates how the alloying with Co and Ni and chloride-induced nanoscale pitting in Zr-Ni-Al-based metallic glasses can be used to generate nanoporous surfaces via depassivating agents. Partial substitution of Ni with Co or Fe creates catalytically active Ni-Co and Ni-Fe surface layers during dealloying while enhancing the ability to form glasses. In NaCl, all glasses exhibit a lower corrosion rate than pure Zr but reduced pitting resistance due to Al. Electrochemical impedance spectroscopy and anodic polarization reveal that Fe impairs repassivation more severely than Co does. Thiocyanate ions induce a negative shift via complexation with Zr, and increasing SCN − destabilises passivity, as can be seen from the presence of multiple corrosion potentials. A mixed Cl − /SCN − electrolyte exhibits an additive effect. Potentiostatic polarisation at selected potentials enables controlled surface modification: at the pitting potential, the selective dissolution of Zr and Al results in significant Ni enrichment. X-ray photoelectron spectroscopy confirms the transition from a hydrated Zr-rich film to a Ni-enriched oxide surface. Crucially, uniform nanoscale pitting at controlled potentials provides a rationale for selecting depassivating agents to induce homogeneous nanoporous architectures, paving the way for water-splitting electrocatalysts.