Stability-Limited Electrocatalytic Behavior of ZnSe and ZnTe during the HER, OER, and ORR.

Zinc chalcogenides have recently attracted interest as earth-abundant electrocatalysts for energy conversion reactions. However, their electrochemical stability under operating conditions remains poorly understood. In this work, the reaction-dependent stability of ZnSe and ZnTe electrocatalysts was systematically investigated under hydrogen-evolution, oxygen-evolution, and oxygen-reduction conditions in an alkaline electrolyte. Electrochemical measurements were combined with structural and surface-sensitive characterization, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry, to probe catalyst evolution associated with electrochemical operation. Thermodynamic analysis based on density functional theory-derived Pourbaix diagrams indicates that both ZnSe and ZnTe lie outside their stability domains over much of the investigated potential range. Consistent with these predictions, experiments show that ZnTe undergoes pronounced morphological degradation, surface oxidation, and substantial dissolution of Zn and Te species into the electrolyte during electrochemical measurement (∼200 ppb). In contrast, ZnSe exhibits comparatively moderate surface restructuring and significantly lower dissolution (∼30 ppb), suggesting more limited degradation under the investigated conditions despite its predicted thermodynamic instability. Passive-immersion controls further show that both materials undergo measurable dissolution in 0.1 M KOH without an applied potential, while electrochemical testing substantially increases Zn and Te dissolution from ZnTe and increases Zn dissolution from ZnSe. Notably, sustained electrochemical current responses were observed even as extensive material transformation occurred, highlighting that a measurable electrochemical response can coincide with catalyst degradation. Furthermore, this systematic investigation reveals that ZnTe exhibits a greater extent of dissolution than ZnSe under all investigated electrochemical conditions, a trend that cannot be predicted from thermodynamic analyses such as Pourbaix diagrams alone. These results demonstrate that the electrochemical behavior of zinc chalcogenides is strongly governed by stability-limited surface reconstruction and dissolution processes. More broadly, this work underscores the importance of integrating thermodynamic analysis with post-reaction characterization when evaluating emerging electrocatalysts for electrochemical energy technologies.