Homolytic versus Heterolytic Hydrogen Evolution Reaction Steered by a Steric Effect
Xiaojun Guo1, Ni Wang1, Xialiang Li1
1Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China.
Angewandte Chemie (International Ed. in English)
|February 28, 2020
Summary
Researchers demonstrate controllable switching between homolytic and heterolytic hydrogen evolution reaction (HER) mechanisms using engineered nickel porphyrin catalysts. This molecular engineering advance offers new insights into HER catalysis.
Area of Science:
- Electrochemistry
- Catalysis
- Materials Science
Background:
- Hydrogen evolution reaction (HER) is crucial for sustainable energy. Understanding HER mechanisms is vital for designing efficient catalysts.
- Existing knowledge on HER pathways, including homolytic and heterolytic bond formation, is incomplete.
Purpose of the Study:
- To investigate the controllable switching between homolytic and heterolytic mechanisms in the hydrogen evolution reaction.
- To design and synthesize novel nickel(II) porphyrin catalysts with tunable steric properties.
Main Methods:
- Synthesis of three nickel(II) porphyrins with varying steric bulk on meso-phenyl groups.
- Electrocatalytic evaluation of the synthesized porphyrins for HER.
- Analysis of reaction intermediates, specifically nickel hydrides, to elucidate reaction pathways.
Main Results:
- The synthesized nickel porphyrins displayed distinct catalytic HER behaviors.
- Steric effects of the porphyrin ligands influenced the H-H bond formation pathway.
- Demonstrated a switch between homolytic and heterolytic pathways based on molecular design.
Conclusions:
- Molecular engineering of porphyrin ligands enables control over HER mechanisms.
- This work provides an unprecedented example of switching between homolytic and heterolytic HER pathways.
- Findings are significant for the rational design of advanced electrocatalysts for hydrogen production.
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