The MXene group of materials possesses a wide range of capabilities. An international research team has recently shown that with the right modifications, MXenes can serve as outstanding catalysts for the oxygen evolution reaction (OER) during electrolytic water splitting. These MXenes are found to be more stable and effective compared to the top metal oxide catalysts currently available. The team is now conducting thorough evaluations of these MXene catalysts for water splitting at BESSY II in Berlin and at the Soleil Synchrotron in France.
The MXene group of materials possesses a wide range of capabilities. An international research team led by HZB chemist Michelle Browne has recently shown that when properly modified, MXenes can serve as outstanding catalysts for the oxygen evolution reaction (OER) during electrolytic water splitting. These MXenes are more stable and effective compared to the top metal oxide catalysts currently available. The team is currently engaged in extensive evaluations of these MXene catalysts for water splitting at the Berlin X-ray source BESSY II and the Soleil Synchrotron in France.
Green hydrogen is emerging as a promising energy storage method for the future. This gas can be produced in an environmentally friendly way by using renewable electricity from solar or wind sources to split water through electrolysis. While one electrode generates hydrogen molecules, oxygen molecules are produced at the other. The oxygen evolution reaction (OER) is a crucial process in electrolysis. To facilitate this reaction, specialized catalysts are required. Nickel oxides are among the leading options for OER catalysts due to their affordability and availability. However, they tend to corrode quickly in the alkaline conditions of an electrolyzer and suffer from poor conductivity. This presents a barrier to the creation of cost-effective, high-efficiency electrolysis systems.
MXenes as Catalysts
A new category of materials, known as MXenes, could provide a viable alternative. These materials are layered structures made of metals such as titanium or vanadium, combined with carbon and/or nitrogen. MXenes have an exceptionally large internal surface area, which can be utilized effectively for charge storage or as catalysts.
Dr. Michelle Browne and her international research team have explored the potential of MXenes as catalysts for the oxygen evolution reaction. PhD student Bastian Schmiedecke chemically modified the MXenes by attaching copper and cobalt hydroxides to their surfaces. Initial tests demonstrated that these catalysts were significantly more efficient than their pure metal oxide counterparts. Additionally, the catalysts maintained their performance without degradation and even showed improved efficiency during prolonged use.
Insights from BESSY II Measurements
Measurements conducted at the BESSY II X-ray source, with contributions from Namrata Sharma and Tristan Petit, revealed the reasons behind the effectiveness of MXenes: “We utilized the Maxymus beamline to investigate how the exterior surfaces of the MXene samples differ from the internal structures,” Schmiedecke explains. The researchers employed a combination of scanning electron microscopy (SEM/TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray transmission microscopy (STXM), and X-ray absorption near-edge structure (XANES) to gain deeper insights into the materials.
Future Directions: Continuous Load Observation
“We have demonstrated that MXenes exhibit significant potential as catalysts in electrolysers,” notes Michelle Browne. The partnership with teams from Trinity College Dublin in Ireland and the University of Chemistry and Technology in Prague will continue. Besides exploring further chemical variations of MXene catalysts, the team aims to test these catalysts in standard electrolysers under continuous operation.
