Research Highlight | Chemical Sciences and Engineering
pH-driven hydration and Rb+ adsorption at alumina–water interfaces
In a study published in the Journal of the American Chemical Society, scientists revealed how pH controls hydration and Rb+ adsorption at alumina–water interfaces, advancing understanding of ion transport at oxide surfaces.
pH-dependent evolution of the EDL at the alumina (012)–water interface, showing shifts in primary hydration-layers (Wₐₔ₁ and Wₐₔₛ₂), increased Rb+ uptake, and Stern-layer contraction by changing IS Rb⁺ heights with increasing pH.
Scientific Achievement
Multimodal in situ experiments and first-principles simulations were used to resolve the pH-driven restructuring of the electrical double-layer (EDL) at the alumina (012)–water interface.
Significance and Impact
The study reveals how surface acid–base chemistry controls the coupled evolution of the interfacial hydration structure, ion sorption, and electrokinetic properties of the EDL at oxide–water interfaces, providing a molecular-scale picture for engineering ion transport in geochemical, catalytic, and electrochemical systems.
Research Details
Changes in the EDL structure with increasing pH include both interfacial hydration layers and associated adsorption structure of Rb+ in the Stern layer:
- Two adsorbed water layers (Wads1 and Wads2) each shift closer to the surface upon deprotonation of bridging and terminal oxygens (OB and OT).
- The Rb+ adsorption coverage increases while the mean adsorption height decreases, indicating Stern-layer contraction.
- These observations are confirmed independently with streaming-potential data and ab initio molecular dynamics simulations.
DOI: 10.1021/jacs.5c21453