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Investigation of Immobilization Effects on Ni(P2N2)2 Electrocatalysts
Felix M Brunner1, Michael L Neville1, Clifford P Kubiak1
1Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093-0358, United States.
Inorganic Chemistry
|November 16, 2020
Summary
Researchers developed a new method to attach nickel catalysts to electrodes using phosphonate groups. This new P-attached catalyst shows improved stability and efficiency for hydrogen evolution reactions (HER) compared to previous N-attached versions.
Area of Science:
- Coordination Chemistry
- Electrocatalysis
- Materials Science
Background:
- Nickel complexes of the type Ni(P2N2)2^2+ are recognized electrocatalysts for the hydrogen evolution reaction (HER).
- Previous immobilization strategies often relied on amine functional groups, potentially impacting catalytic activity.
- A need exists for alternative attachment methods to enhance catalyst performance and stability.
Purpose of the Study:
- To develop a novel synthetic route for Ni(P2N2)2^2+ complexes with phosphonate substituents.
- To investigate the immobilization of these new complexes onto electrode surfaces via phosphonate groups.
- To compare the electrocatalytic performance and stability of P-attached versus N-attached Ni(P2N2)2^2+ catalysts for HER.
Main Methods:
- Synthesis of phosphonate-modified P2N2 ligands and their corresponding nickel complexes.
- Post-synthetic modification of existing ligands.
- Characterization of synthesized complexes using spectroscopic and analytical techniques.
- Covalent attachment of phosphonate-functionalized complexes to mesoporous TiO2 electrodes.
- Electrochemical evaluation of immobilized catalysts for hydrogen evolution reaction (HER).
Main Results:
- Successful synthesis and characterization of phosphonate-functionalized Ni(P2N2)2^2+ complexes.
- Demonstration of covalent attachment to TiO2 electrodes via phosphonate groups, preserving amine functionalities.
- Immobilized catalysts exhibited competent and stable electrocatalytic activity for HER in aqueous solution at mild pH and low overpotential.
- The P-attached catalyst demonstrated a 9-14% higher turnover number compared to the N-attached counterpart.
Conclusions:
- A new synthetic strategy enables the preparation of Ni(P2N2)2^2+ catalysts functionalized for phosphonate-based electrode attachment.
- Phosphonate immobilization offers a viable alternative to amine-based attachment, potentially preserving key catalytic functionalities.
- The P-attached catalyst exhibits enhanced performance and stability for sustained HER, highlighting the benefits of this immobilization approach.
