Homogeneous vs. heterogeneous catalysis for hydrogen evolution by a nickel(ii) bis(diphosphine) complex
Giovanni Bergamini1, Mirco Natali
1Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via L. Borsari 46, 44121, Ferrara, Italy. mirco.natali@unife.it.
Dalton Transactions (Cambridge, England : 2003)
|September 20, 2019
Summary
A novel nickel complex efficiently catalyzes hydrogen evolution under homogeneous conditions. However, grafting it onto a TiO2 surface led to rapid deactivation, indicating challenges in heterogeneous catalyst design.
Area of Science:
- Inorganic Chemistry
- Catalysis
- Materials Science
Background:
- Developing efficient catalysts for the hydrogen evolution reaction (HER) is crucial for sustainable energy technologies.
- Molecular catalysts offer tunable properties but face challenges in stability and recyclability in heterogeneous systems.
- Understanding the interplay between catalyst structure and immobilization is key to designing effective heterogeneous catalysts.
Purpose of the Study:
- To synthesize and characterize a novel nickel(II) bis(diphosphine) complex with peripheral carboxylic acid groups.
- To evaluate the catalytic performance of this complex for the hydrogen evolution reaction (HER) under various conditions.
- To investigate the impact of immobilization onto a mesoporous TiO2 support on catalytic activity and stability.
Main Methods:
- Synthesis and characterization of the nickel(II) complex.
- Homogeneous electrocatalysis in acetonitrile with trifluoroacetic acid.
- Homogeneous photocatalysis in aqueous solution using Ru(bpy)32+ and ascorbic acid.
- Heterogeneous electrocatalysis after grafting the complex onto mesoporous TiO2.
Main Results:
- The nickel complex demonstrated competent and efficient catalytic activity for HER under homogeneous electro- and photochemical conditions.
- Upon covalent grafting onto mesoporous TiO2, the catalyst exhibited rapid deactivation.
- Catalyst deactivation in the heterogeneous system is attributed to the binding mode and structural rigidity introduced by grafting.
Conclusions:
- The designed nickel complex is a promising molecular catalyst for hydrogen evolution.
- Direct transposition of homogeneous molecular catalysis to heterogeneous systems requires careful consideration of catalyst immobilization strategies.
- Catalyst design must account for structural and electronic modifications upon surface attachment for effective heterogeneous applications.
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