Cobalt-Iron-Phosphate Hydrogen Evolution Reaction Electrocatalyst for Solar-Driven Alkaline Seawater Electrolyzer

Area of Science:

• Electrochemistry
• Materials Science
• Renewable Energy

Background:

• Seawater splitting is a promising, cost-effective method for hydrogen production without prior desalination.
• Developing highly active and durable electrocatalysts is crucial for efficient seawater splitting.
• Existing precious metal catalysts are expensive and can be limited by durability in seawater environments.

Purpose of the Study:

• To synthesize and evaluate a novel cobalt-iron-phosphate ((Co,Fe)PO4) electrocatalyst for hydrogen evolution reaction (HER) in alkaline seawater splitting.
• To demonstrate the high activity and durability of the developed electrocatalyst.
• To compare the performance of an electrolyzer using this non-precious metal catalyst against one using precious metal catalysts.

Main Methods:

• Phosphidation-based synthesis of cobalt-iron-phosphate ((Co,Fe)PO4).
• Electrochemical characterization of HER activity and durability in alkaline natural seawater (1 M KOH + seawater).
• Performance testing of an alkaline seawater electrolyzer with the developed catalyst compared to precious metal catalysts.

Main Results:

• The (Co,Fe)PO4 electrocatalyst achieved a current density of 10 mA/cm2 at an overpotential of 137 mV in alkaline seawater.
• The catalyst demonstrated excellent stability, with no noticeable degradation over 72 hours of continuous operation at -100 mA/cm2.
• An electrolyzer using the non-precious metal (Co,Fe)PO4 catalyst showed superior performance (1.625 V at 10 mA/cm2) compared to precious metal catalysts (1.653 V at 10 mA/cm2).
• A high solar-to-hydrogen (STH) efficiency of 12.8% was achieved using the non-precious metal-based alkaline seawater electrolyzer with a commercial silicon solar cell.

Conclusions:

• The phosphidation-derived (Co,Fe)PO4 is a highly active and durable electrocatalyst for alkaline seawater splitting.
• This non-precious metal catalyst offers a competitive and potentially more economical alternative to precious metal catalysts for hydrogen production.
• The developed electrolyzer system shows significant potential for efficient and sustainable hydrogen generation from seawater.