Exploring Active Sites in Multi-Heteroatom-Doped Co-Based Catalysts for Hydrogen Evolution Reactions
Ali Shahraei1,2, Ioanna Martinaiou1,3, K Alexander Creutz3
1TU Darmstadt, Graduate School of Excellence Energy Science and Engineering, Otto-Berndt-Str. 3, 64287, Darmstadt, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|June 5, 2018
Summary
Cobalt-nitrogen-sulfur doped carbon materials catalyze the hydrogen evolution reaction (HER). Researchers found that cobalt-nitrogen (CoNx) sites, not cobalt-sulfur (CoSy) sites, dominate HER activity and stability in acidic electrolytes.
Area of Science:
- Materials Science
- Electrochemistry
- Catalysis
Background:
- Metal-nitrogen and metal-sulfur doped carbon materials are known electrocatalysts for the hydrogen evolution reaction (HER).
- Co-doped carbon materials with nitrogen and sulfur heteroatoms show high HER activity, but the specific active sites (M-Nx vs. M-Sy) remain debated.
- Understanding the structure-activity relationship is crucial for designing efficient electrocatalysts for hydrogen production.
Purpose of the Study:
- To investigate the effect of cobalt content on multi-heteroatom doped carbon materials for the hydrogen evolution reaction (HER) in an acidic medium.
- To elucidate whether cobalt-nitrogen (CoNx) or cobalt-sulfur (CoSy) sites are primarily responsible for the observed catalytic activity.
- To establish a structure-performance relationship for these advanced HER electrocatalysts.
Main Methods:
- Synthesis of multi-heteroatom (N and S) doped carbon materials with varying cobalt content using a simple doping method.
- Structural characterization using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM) to identify and confirm CoNx and CoSy sites.
- Electrochemical evaluation of HER performance in acidic medium, including activity measurements and long-term stability tests under galvanostatic conditions.
Main Results:
- The presence of sulfur in the doped carbon materials facilitated the formation of a greater number of CoNx sites.
- Electrochemical studies demonstrated that the HER activity was predominantly governed by CoNx sites, outperforming CoSy sites.
- The most active catalysts exhibited remarkable stability during prolonged galvanostatic operation, indicating their potential for practical applications.
Conclusions:
- The study confirms that CoNx sites are the primary active centers for the hydrogen evolution reaction in Co-N-S doped carbon materials.
- The presence of sulfur plays a crucial role in enhancing the formation of these highly active CoNx sites.
- These findings provide valuable insights for the rational design of efficient and stable electrocatalysts for hydrogen production in electrolyzers.
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