Reoriented Interfacial Water Structure Around Pd Enhances Oxygen Reduction Kinetics in Zn-Methanol-Air Batteries.

Area of Science:

• Materials Science and Engineering
• Electrochemistry
• Catalysis

Background:

• Interfacial water dynamics in the electrical double layer (EDL) are crucial for electrocatalysis.
• Tuning EDL properties often involves electrolyte modification, but catalyst design for interfacial water structure is underexplored.
• Optimizing charge transfer requires understanding and controlling the catalyst-water interface.

Purpose of the Study:

• To develop a composite catalyst that tailors interfacial water structure for enhanced electrocatalysis.
• To investigate the mechanism by which catalyst design influences EDL properties and water orientation.
• To evaluate the performance of the new catalyst in oxygen reduction and methanol oxidation reactions and its application in batteries.

Main Methods:

• Synthesis of a composite catalyst: atomically dispersed cobalt sites (Co_SA) in a N-doped carbon matrix with palladium nanoparticles (PdCo_NP@Co_SANC).
• Utilized in situ spectroscopy and density functional theory (DFT) calculations to probe interfacial water structure and electronic properties.
• Electrochemical testing for oxygen reduction reaction (ORR), methanol oxidation reaction (MOR), and construction of a Zn-methanol-air battery.

Main Results:

• Co_SA incorporation shifted the potential of zero charge (E_PZC) negatively, creating a more positively charged surface.
• This charge redistribution reoriented interfacial water from H-down to O-down, promoting *OH hydrogenation.
• The PdCo_NP@Co_SANC catalyst exhibited superior ORR (0.937 V half-wave potential) and MOR activity, outperforming controls and commercial Pd/C, and enabled stable battery operation (>2500 h).

Conclusions:

• Catalyst design is a viable strategy to tune interfacial water structure and enhance electrocatalytic performance.
• The PdCo_NP@Co_SANC catalyst demonstrates significant potential for ORR, MOR, and energy storage applications.
• Understanding the interplay between catalyst properties, EDL, and interfacial water is key to designing next-generation electrocatalysts.