Researchers from USTC reported atomic-level identification of dynamic structure of catalytically active sites under alkaline hydrogen evolution reaction
A team of researchers from University of Science and Technology of China’s (USTC) National Synchrotron Radiation Laboratory (NSRL), in collaboration with School of Chemistry and Materials Science, developed an operando synchrotron radiation X-ray absorption fine structure spectroscopy (XAFS) technology combined with theoretical calculations. The team used the operando XAFS method to identify the realistic structure and dynamic evolution of active sites in cobalt-based catalysts at the atomic level during electrocatalytic hydrogen evolution reaction (HER) in alkaline electrolyte. The research was published in the journal Natural Catalysis on January 1, 2019.
The Beijing Synchrotron Radiation Facility (BSRF) and Shanghai Synchrotron Radiation Facility (SSRF) established an operando XAFS measurement that assisted to monitor the evolutions of atomic and electronic structures in a uniform cobalt-based single-atom catalyst under alkaline HER condition. The team found that the electrocatalyst experienced structural reconstruction into a high-valence ‘HO-Co1-N2’ moiety, which was attributed to the binding between initial isolated ‘Co1-N4’ sites with electrolyte hydroxide. Water molecular were adsorbed to the active center to the form ‘H2O-(HO-Co1-N2)’ reaction intermediates that were driven by the applied overpotential. The team performed theoretical calculations and confirmed the configurations of these intermediates and revealed the mechanism of the reaction.
Commercial platinum on carbon catalyst (Pt/C) is currently recognized as a highly efficient and stable electrocatalyst for HER. The team found that the performance and stability of the new electrocatalyst are closely identical to commercial Pt/C electrocatalyst. Moreover, the cost required in production is less than half of that of Pt/C. To determine the high sensitivity of the active sites in the electrocatalytic process, the team used operando synchrotron radiation spectroscopy and showed the mechanism of the catalysts in the actual working state. The operando synchrotron radiation spectroscopy technique can also be used for studying the dynamic process of the surface/interface of catalytic materials in other photo-/electric energy conversion reactions. The researchers stated that the findings offer experimental basis and theoretical guidance for analyzing the structure and reaction mechanism of catalytically active centers at the atomic scale. Moreover, the research also offers new notions for designing efficient energy conversion materials.