Spectro-Electrochemical Decoding of Metals, Alloys, and Buried Interfaces

Metal-electrolyte interfaces govern corrosion, catalysis, energy-conversion and storage technologies, yet resolving their chemical evolution under operating conditions remains challenging. Electrochemical measurements report an integrated response, while post-mortem characterization can lose the transient sequence and spatial distribution of dissolved species. Here, we introduce the In-Situ Corrosion Monitoring Technique (ICMT), an operando spectro-electrochemical platform that converts interfacial metal dissolution into spatially and temporally resolved optical concentration fields. Under an applied bias, dissolution products migrate through a transparent gel electrolyte that suppresses convection and restricts mixing, thereby retaining dissolved species for interrogation by UV-visible spectroscopy. Using Cu and Ni as model systems, ICMT establishes element-specific absorption fingerprints and distinguishes active Ni dissolution from passivation-influenced Cu corrosion while enabling estimation of recession rates and apparent transport coefficients. Applied to Cu-coated Ni, ICMT sequentially detects Cu and Ni-associated species, revealing degradation from the outer coating to the buried substrate and detecting dissolution from a Cu overlayer as thin as 100 nm. Applied to a Cu-Zn-Ni ternary alloy, the platform resolves constituent-specific dissolution signatures that remain convoluted within the total electrochemical current. Collectively, ICMT provides a simple and accessible benchtop approach for determining how material interface evolves, which constituent dissolves and from which layer it arises, while preserving the transient chemical history of electrochemical interfaces.