Hydrogen is a ubiquitous impurity that deteriorates the metal/oxide interface, causing challenges such as current leakage and blistering. Here, we uncover the mechanisms behind hydrogen-induced damage at the prototypical $\mathrm{Al}/\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ interface. The precursor that we identify is charge trapping at the interface, which facilitates hydrogen segregation to the interface plane as ${\mathrm{H}}^{-}$. Presence of hydrogen increases aluminum vacancy concentration at the interfacial metal and oxide planes. Each Al vacancy can trap multiple hydrogen atoms. As a result, the interfacial aluminum vacancy and hydrogen concentrations increase by orders of magnitude. Additionally, hydrogen behaves as an $n$-type dopant and increases electronic conductivity at the oxide layer adjacent to the interface by forming ${\mathrm{H}}^{+}$, and the $\left[{\mathrm{V}}_{\mathrm{Al}}\text{−}\mathrm{H}\right]$ complex is the predominant defect at this layer. These findings provide the precursor mechanisms of hydrogen-induced damage at the metal-oxide interfaces and have implications for advancing $\mathrm{Al}/\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3\text{−}\mathrm{based}$ coatings and electronic devices.

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• Chemical bonding
• Defects
• Doping effects
• Electronic structure
• Hydrogen bonds
• Thermodynamics
• Interfaces
• Density functional theory