Zinc-based alloys are promising candidates for alkaline electrochemical systems, yet their hydrogen evolution reactivity, microstructural stability, and degradation pathways remain strongly dependent on alloy composition. In particular, Sn additions to Zn can simultaneously modify the hydrogen evolution reaction (HER) kinetics and the mechanical integrity of the electrode during cycling, but a systematic correlation between Sn content, microstructure, and electrochemical behavior is still lacking. In this work, we comparatively investigate three Zn-Sn alloys with different Sn contents and bare Zn to elucidate how alloying level governs surface activation, gas evolution, and long-term stability under alkaline operation.

Electrochemical characterization is carried out using HER polarization measurements, Tafel analysis, symmetric Zn-Zn cell testing, and cyclic (charge-discharge) cell protocols in concentrated alkaline electrolyte. From these measurements, we extract key kinetic parameters such as HER overpotential, Tafel slope, and exchange current density, as well as galvanostatic cycling stability, polarization hysteresis, and interfacial resistance evolution. In parallel, operando optical microscopy is employed to directly monitor bubble nucleation, surface roughening, and morphological changes of the Zn-Sn electrodes under bias, providing real-time visualization of degradation and gas evolution behavior as a function of alloy composition.

To establish structure-property relationships, we combine X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD) before and after electrochemical testing. XRD and TEM are used to identify phases, grain size, and possible intermetallic formation, while EBSD maps grain orientation, texture, and local misorientation to reveal microstructural heterogeneity and damage accumulation. Post-mortem SEM/EBSD analysis after cycling enables us to correlate crack formation, grain boundary attack, and phase redistribution with the observed electrochemical performance.

By comparing the three Zn-Sn alloys across this integrated electrochemical and microstructural dataset, we demonstrate how varying Sn content influences HER activity, electrode polarization, and the onset of performance-limiting degradation modes. The results provide design guidelines for optimizing Zn-Sn alloy composition and microstructure for use as robust, hydrogen-tolerant electrodes in alkaline energy storage and conversion technologies, including Zn-based rechargeable systems.