Decoupling H‑Release and OH^- Management at Pd@TiO₂ Interfaces for Efficient Alkaline Hydrogen Oxidation Reaction

Area of Science:

• Electrochemistry and catalysis
• Materials science for energy applications

Background:

• Understanding catalyst degradation and reaction mechanisms is crucial for advancing the alkaline hydrogen oxidation reaction (HOR).
• Existing palladium-based catalysts (Pd/C) suffer from degradation issues, limiting their long-term performance in alkaline media.

Purpose of the Study:

• To investigate catalyst degradation pathways and reaction mechanisms in the alkaline HOR.
• To develop a more stable and efficient catalyst for the alkaline HOR using a core-shell nanostructure.

Main Methods:

• Synthesis of a core-shell Pd@TiO₂/C catalyst via thermal reduction and atomic layer deposition.
• Characterization using identical location transmission electron microscopy (IL-TEM) for degradation analysis.
• Operando X-ray absorption spectroscopy (XAS) to study reaction mechanisms under device-relevant conditions.

Main Results:

• The Pd@TiO₂/C catalyst achieved a mass exchange current density (j ^0,m) of 97.5 mA mg_Pd^-1, over three times higher than uncoated Pd/C (27.5 mA mg_Pd^-1).
• IL-TEM revealed that the TiO₂ shell effectively suppressed the growth-detachment degradation pathway observed in Pd/C catalysts.
• Operando XAS demonstrated that Pd core facilitates hydrogen dissociation and PdH_x formation, while the TiO₂ shell aids hydrogen desorption and OH^- adsorption.

Conclusions:

• The TiO₂ shell provides dual functionality: stabilizing the Pd core against degradation and actively participating in the catalytic cycle.
• The core-shell Pd@TiO₂/C catalyst exhibits superior stability and enhanced kinetics for the alkaline HOR.
• This study presents a promising strategy for designing durable and efficient electrocatalysts for alkaline HOR applications.