Lattice Distortion Controlled Oxygen Ion Transport Governs Interlayer Stability and OER Kinetics in Sn--Sb--RuO\textsubscript{x}/$\beta$-PbO\textsubscript{2} Anodes
Abstract
Porous $\beta$-PbO\textsubscript{2} anodes supported on Ti are attractive OER electrocatalysts for zinc electrowinning, yet lifetime is limited by interfacial TiO\textsubscript{2} growth and chloride-assisted radical chemistry. Here we provide a mechanistic account of the stabilizing role of Ru in Sn--Sb--RuO\textsubscript{x} interlayers. Combining density functional theory with nudged elastic band (DFT/NEB) calculations, depth-resolved XPS/ToF-SIMS, electrochemical impedance spectroscopy (EIS), and accelerated ageing, we show that Ru substitution in a rutile-like SnO\textsubscript{2}:Sb matrix introduces local lattice distortion that increases the oxygen-ion migration barrier $\Delta G^{\ddagger}_{\mathrm{mig}}$ by \SI{100}{\milli\electronvolt}, from \SI{0.60 \pm 0.03}{\electronvolt} (Ru-free) to \SI{0.70 \pm 0.04}{\electronvolt} (1.0~at.\% Ru). The higher barrier reduces O\textsuperscript{2-} flux toward Ti, suppressing sub-stoichiometric TiO\textsubscript{2-$\delta$} formation and lowering both film resistance and charge-transfer resistance during OER: $R_f$ decreases from \SI{0.12 \pm 0.02}{\ohm\centi\meter\squared} to \SI{0.08 \pm 0.01}{\ohm\centi\meter\squared}, and $R_{ct}$ from \SI{60 \pm 7}{\ohm\centi\meter\squared} to \SI{40 \pm 5}{\ohm\centi\meter\squared}. Under \SI{150}{g\,L^{-1}} H\textsubscript{2}SO\textsubscript{4} with \SI{1.0}{\milli\gram\per\liter} Cl\textsuperscript{--} at \SI{40}{\celsius}, the early-time $R_f$ drift rate improves from \SI{1.0 \pm 0.2}{\milli\ohm\centi\meter\squared\per\hour} to \SI{0.65 \pm 0.15}{\milli\ohm\centi\meter\squared\per\hour}, extending the time-to-threshold (+\SI{200}{\milli\volt} rise) from \SI{65 \pm 8}{\hour} to \SI{95 \pm 10}{\hour}. We establish quantitative correlations among Ru at.\%, $\Delta G^{\ddagger}_{\mathrm{mig}}$, interfacial TiO\textsubscript{2} growth, and lifetime, elevating Ru from a mere conductive dopant'' to a \emph{lattice-transport regulator} and yielding design rules for Ru-lean interlayers that preserve durability and performance.