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A Nickel Dithiolate Water Reduction Catalyst Providing Ligand-Based Proton-Coupled Electron-Transfer Pathways
Keita Koshiba1,2, Kosei Yamauchi1,2, Ken Sakai1,2,3
1Department of Chemistry, Faculty of Science, Kyushu University, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan.
Angewandte Chemie (International Ed. in English)
|March 10, 2017
Summary
A novel nickel pyrazinedithiolate catalyst efficiently drives hydrogen evolution reaction (HER) catalysis. This molecular catalyst operates at low overpotentials and high efficiency, showcasing a unique proton-coupled electron-transfer mechanism.
Area of Science:
- Electrochemistry
- Catalysis
- Materials Science
Background:
- The hydrogen evolution reaction (HER) is crucial for sustainable energy production.
- Developing efficient and cost-effective molecular catalysts for HER is a key research area.
- Mimicking the active sites of natural enzymes, like [NiFe] hydrogenase, offers a promising strategy for catalyst design.
Purpose of the Study:
- To investigate the catalytic activity of a nickel pyrazinedithiolate complex for the hydrogen evolution reaction (HER).
- To elucidate the mechanism of HER catalyzed by this nickel complex, particularly focusing on proton-coupled electron-transfer (PCET) pathways.
- To evaluate the efficiency, overpotential, and stability of the nickel catalyst under relevant conditions.
Main Methods:
- Synthesis and characterization of the nickel pyrazinedithiolate complex ([Ni(dcpdt)2 ]2-).
- Electrochemical studies to assess catalytic activity for HER, including overpotential and Faradaic efficiency measurements.
- Density Functional Theory (DFT) calculations to investigate reaction mechanisms and intermediate species.
Main Results:
- The nickel pyrazinedithiolate complex demonstrated efficient molecular catalysis for HER with low overpotentials (330-400 mV at pH 4-6).
- High turnover numbers (20,000) and Faradaic efficiency (92-100%) were achieved over 24 hours of electrolysis.
- Electrochemical and DFT studies revealed a ligand-based PCET mechanism involving diprotonated species at pH < 6.4, avoiding the need for low-valent nickel intermediates.
Conclusions:
- Nickel pyrazinedithiolate serves as an efficient molecular catalyst for HER, mimicking the NiS4 core of [NiFe] hydrogenase.
- The catalyst operates via an unprecedented ligand-based PCET pathway, enabling efficient HER at moderate potentials.
- This work presents the first example of a catalyst exhibiting such a mechanism for electrocatalytic hydrogen production.
Keywords:
artificial photosynthesishydrogen evolutionnickel complexesproton-coupled electron transfer (PCET)pyrazineMore Related Videos
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