Regio‐Selective Electrocatalysis in Single‐Wall Carbon Nanotubes: Platinum Inside for Hydrogen Evolution Reaction/Hydrogen Oxidation Reaction and Ruthenium Outside for Oxygen Evolution Reaction

Developing selective and durable electrocatalysts remains a key challenge for the development of electrolyzers and unitized regenerative fuel cells (URFCs). Herein, we explore a novel approach toward specific reactions in water splitting, where one of the catalysts (Pt) is confined inside single‐wall carbon nanotubes (SWCNTs) for specific hydrogen evolution/oxidation reaction (HER/HOR), while the second catalyst (Ru/RuO x ) is located outside the SWCNTs for specific oxygen evolution reaction (OER), yielding a Pt@SWCNT@Ru catalyst with spatially separated inner and outer active sites. Encapsulation within SWCNTs also enhances Fe 3+ tolerance compared to Pt/C. Long‐term chronoamperometry reveals stable HER currents over 84 h and distinct Ru activation/decay kinetics over 72 h under acidic OER, while inductively coupled plasma optical emission spectroscopy shows no detectable Pt or Ru dissolution, indicating that spatial separation of Pt is likely to be preserved. These findings establish Pt@SWCNT@Ru as a proof‐of‐concept platform for spatially resolved, multifunctional electrodes relevant to next‑generation URFC architectures.