Synthesis of Pellet-Based Pd/C Egg-Shell Catalysts for Reversible Hydrogen Storage in Formate/Bicarbonate

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Hydrogen storage is crucial for renewable energy applications.
• Developing safe, efficient, and easily handled hydrogen storage materials remains a challenge.
• Palladium on carbon (Pd/C) catalysts show promise for reversible hydrogen storage cycles.

Purpose of the Study:

• To develop a scalable synthesis of egg-shell Pd/C pellet catalysts.
• To evaluate the catalyst's performance in the reversible formate/bicarbonate hydrogen-storage cycle.
• To investigate catalyst stability and reactivation strategies.

Main Methods:

• Scalable synthesis of egg-shell Pd/C pellet catalysts using oxalic acid as a chelating additive.
• Testing catalyst activity in both formate dehydrogenation and bicarbonate hydrogenation half-reactions.
• Evaluating hydrogen release rates, total hydrogen yield, and turnover numbers/frequencies (TON/TOF).

Main Results:

• Achieved scalable synthesis of uniform, thin Pd shells on carbon pellets.
• Demonstrated high catalytic activity in both reaction directions, with hydrogen release rates up to 17.4 L h^-1.
• Obtained CO-free hydrogen yield of 80 L with TON/TOF values comparable to state-of-the-art powder catalysts.
• Provided insights into catalyst reactivation for improved stability during repeated use.

Conclusions:

• The egg-shell Pd/C pellet catalyst offers a safe, nontoxic, and easily controllable system for hydrogen storage.
• Pelletized catalysts provide handling advantages over powder systems while maintaining high performance.
• The developed catalyst and reactivation strategies show significant potential for practical hydrogen storage applications.