Scientists from the Chinese Academy of Sciences’ Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) and their associates have created an effective electrocatalyst named Co-N/S-HCS that exhibits exceptional activity and stability in seawater electrolysis, according to a study published in Chem Catalysis on November 13th, 2024.
The DFT-optimized atomic configurations of oxygen intermediates (OOH*, O*, and OH*) adsorbed on symmetric CoN4 and asymmetric CoN3S1 atomic interface models. Image Credit: ZHANG Canhui
Although seawater electrolysis has long been viewed as a viable method for producing hydrogen sustainably, it has encountered several obstacles because of corrosion caused by chloride ions (Cl⁻), which can impair the effectiveness of a catalyst.
This provides a sustainable method of producing sustainable hydrogen requiring minimal freshwater.
Our work has significantly enhanced the catalyst’s resistance to Cl⁻ corrosion by carefully tuning the electronic environment around cobalt atoms. This gives the Co-N/S-HCS both long-term stability and high activity.
Dr. Canhui Zhang, Study First Author and Researcher, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
In the asymmetric CoN₃S₁ structure used by the Co-N/S-HCS electrocatalyst, each cobalt (Co) atom is coordinated with three nitrogen (N) atoms and one sulfur (S) atom.
In contrast to the symmetric CoN4 configuration, this asymmetric CoN₃S₁ configuration, which was optimized using density functional theory and molecular dynamics simulations, alters the electronic distribution around the Co center, weakening corrosive Cl⁻ adsorption and improving the catalyst’s performance in seawater-based electrolytes.
The CoN₃S₁ structure maximizes the catalyst's trifunctional activity by facilitating essential processes like oxygen reduction, oxygen evolution, and hydrogen evolution, while simultaneously reducing the corrosive effects of Cl–.
This multipurpose capability is essential for practical applications in seawater-based energy systems.
Dr. Xingkun Wang, Study Corresponding Author, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
Researchers confirmed their idea by including Co-N/S-HCS in a self-propelled seawater splitting device. This method, when combined with seawater-based Zn-air batteries (S-ZABs) and two-electrode electrolysis devices, performed exceptionally well. The S-ZABs demonstrated cycle stability for up to 650 hours, whereas the two-electrode electrolysis devices performed consistently for more than 1,100 hours.
More significantly, the integrated system has achieved a greater hydrogen production rate of 469 µmol/h, outperforming the CoSA/N, S-HCS system. The rate of hydrogen synthesis with current technologies is 184 µmol/h.
Co-N/S-HCS may be useful for other seawater applications, such desalination and enhanced energy storage, therefore the ramifications of this discovery go beyond just producing hydrogen.
The robustness of Co-N/S-HCS opens up exciting possibilities for sustainable hydrogen production in water-scarce regions, reducing costs and minimizing environmental impact.
Minghua Huang, Study Corresponding Author, Ocean University of China
These results provide a solid basis for creating catalysts that are resistant to seawater. The study demonstrates the possibility for large-scale, sustainable hydrogen production and represents a significant advancement in seawater-based energy options.
Another corresponding author, Prof. Heqing Jiang of QIBEBT added, “We hope this work inspires further advancements in sustainable hydrogen production that can meet global energy demands.”
Journal Reference:
Zhang, C. et. al. (2024) Symmetry-breaking CoN3S1 centers enable inert chloride ion adsorption for facilitating self-driven overall seawater splitting. Chem Catalysis. doi.org/10.1016/j.checat.2024.101169