ALBA Synchrotron
An international study with researchers from China, Spain, Germany and Korea advances low-cost, efficient green energy solutions. They describe how, in alkaline environments, nickel sulfide (NiS) electrodes transform into a mix of Ni3S2 and NiO, creating highly active sites that enhance hydrogen production. Synchrotron light experiments at CLAESS beamline were key to observe this transformation in real time, providing insights into how these changes improve the catalyst's performance.
Unlocking hydrogen as an energy source is essential for the global green transition. However, current hydrogen production methods remain extremely energy-intensive and produce significant carbon dioxide emissions. Water electrolysis, which splits water into hydrogen and oxygen using renewable energy, offers a promising solution. To improve this process, developing low-cost, high-performance electrocatalysts is crucial. These catalysts speed up reactions and lower the activation energy required, particularly in the alkaline conditions common in industry. Current research focuses on creating efficient catalysts with dual active sites using inexpensive, abundant materials like metal chalcogenides, phosphides, and carbides. Despite progress, understanding the exact reaction mechanisms and active sites in alkaline conditions remains challenging.
In a recent study published in Nature Communications, researchers revealed that nickel sulfide (NiS) electrodes transform during use in alkaline conditions, forming highly active dual sites at the Ni3S2/NiO interface. This restructuring greatly enhances catalytic activity, significantly improving their efficiency in the hydrogen evolution reaction (HER). The work involved researchers from Xiamen and Fudan Universities (China), IMDEA Energy (Spain) alongside scientists from the ALBA Synchrotron, the Technical University of Darmstadt (Germany) and the Ulsan National Institute of Science and Technology (UNIST) (Republic of Korea).
To conduct the study, the researchers grew NiS samples on carbon paper electrodes and used various techniques to study the HER process, ranging from electron microscopy for imaging the NiS particles; X-ray diffraction and spectroscopy for the analysis of the NiS samples before and after HER measurements, and a combination of electrochemical and photoemission spectroscopy techniques, including in-situ Raman spectroscopy, for studying in detail the changes of the catalysts during the HER process.
“In particular, the use of operando X-ray absorption spectroscopy (XAS) at the CLAESS beamline at ALBA provided real-time insights into the structural and chemical changes in the catalyst, allowing the researchers to identify active catalytic phases and explain the improved HER performance”, says Laura Simonelli, principal beamline scientist at CLAESS.
This study was the first to observe the transition of NiS into a mixed phase of Ni3S2 and NiO during operation. These newly detected Ni3S2/NiO interfaces create dual sites that accelerate water splitting and reduce overpotential.
The detailed, in-situ study of NiS electrodes has provided valuable information for their optimization for hydrogen production in alkaline environments. Thus, the highly dynamic transition of metal chalcogenides, combined with careful control of working conditions, offers a unique path for developing new high-performance catalytic species, ultimately powering green hydrogen production and supporting the clean energy transition.
Operando Ni K-edge XAS for NiS catalyst as a function of applied voltages.
Reference: Dynamic restructuring of nickel sulfides for electrocatalytic hydrogen evolution reaction.
https://www.nature.com/articles/s41467-024-49015-4