Cyclic Trinickel(II) Clusters in a Metal-Azolate Framework for Efficient Overall Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Efficient electrocatalysts are crucial for overall water splitting to produce clean hydrogen fuel.
• Current state-of-the-art catalysts, often platinum-based, face challenges in cost and long-term stability.
• Developing novel, earth-abundant metal-based catalysts is a key research objective.

Purpose of the Study:

• To synthesize and characterize a new metal-azolate framework (Ni-BTPP) for overall water splitting.
• To evaluate the electrocatalytic performance and stability of Ni-BTPP compared to commercial catalysts.
• To elucidate the catalytic mechanism through theoretical calculations.

Main Methods:

• Synthesis of the metal-azolate framework [Ni3(μ3-O)(BTPP)(OH)(H2O)2] (Ni-BTPP).
• Electrochemical testing in 1.0 M KOH solution, including current density-voltage measurements and long-term stability tests.
• Density functional theory (DFT) calculations to investigate reaction pathways and energy barriers.

Main Results:

• Ni-BTPP achieved a current density of 50 mA cm⁻² at 1.8 V, outperforming 20%Pt/C||IrO2/NF (35.8 mA cm⁻² at 2.0 V).
• The catalyst exhibited excellent stability, with no degradation observed over 12 hours of continuous operation at 50 mA cm⁻².
• Theoretical calculations revealed that the μ3-O atom facilitates water dissociation and provides a low-energy coupling pathway for water oxidation.

Conclusions:

• The Ni-BTPP framework is a highly active and stable electrocatalyst for overall water splitting.
• The unique structure of the cyclic trinickel(II) cluster, particularly the μ3-O atom, is key to its enhanced performance.
• Ni-BTPP presents a promising, cost-effective alternative to precious metal catalysts for hydrogen production.