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In a study just published in Nature Catalysis, a research collaboration between Professor Xiangfeng Duan’s group in the UCLA Department of Chemistry & Biochemistry, Professor Yu Huang’s group in the UCLA Department of Materials Science and Engineering, and Professor William A. Goddard III’s group at the California Institute of Technology, has yielded a groundbreaking discovery in hydrogen evolution reactions (HER) on platinum (Pt) surfaces.

Titled “Edge sites dominate the hydrogen evolution reaction on platinum nanocatalysts” the study uncovers that the edges of platinum nanocatalysts demonstrate a significantly lower free energy activation barrier for HER compared to the (100) and (111) facets. This revelation results in a turnover frequency (TOF) at these edge sites that is 100 to 10,000 times higher than that on (100) and (111) facets.

This research integrates experimental and theoretical approaches and provides new insights into the molecular mechanisms underlying HER on Pt surfaces. The findings suggest that the edge sites on platinum nanocatalysts play a crucial role in enhancing HER activity, offering potential pathways for designing more efficient catalysts.

The team developed a novel technique called Electrical Transport Spectroscopy (ETS) to directly and exclusively probe hydrogen adsorption on the Pt surface, identifying distinct adsorption sites including hydrogen under-potentially deposited (Hupd) and hydrogen over-potentially deposited (Hopd). The Hopd, occurring at the onset of HER, is usually masked by the much larger HER current and has not been previously resolved by conventional cyclic voltammetry. This new study demonstrates that Hopd, originating from edge sites, is the active participant in the reaction. This is contrary to previous assumptions that Hupd is the critical intermediate for HER.

“The ETS approach developed by our team is exclusively sensitive to surface adsorbates but insensitive to catalytic current. It offers powerful approach to directly profile surface adsorbates during catalytic processes and identify the active sites that are difficult to probe previously”, said Duan, Professor of Chemistry at UCLA.

These findings were supported by advanced theoretical calculations, which confirmed that the HER turnover frequency at Pt edge sites is dramatically higher (100 to 10,000 times more active) than that on (100) or (111) terrace sites. This dramatic difference in activity is attributed to the unique coordination environment of the edge sites, which facilitates more efficient hydrogen recombination.

“This study marks a critical breakthrough in understanding the primary active sites in nanoscale catalysts. By identifying edge sites as the most active for HER, it lays the groundwork for designing more efficient Pt-based catalysts,” commented Goddard, Professor of Chemistry, Materials Science, and Applied Physics at Caltech. “Increasing edge sites through nanostructure engineering could enhance catalyst efficiency”.

This discovery results from decade-long collaboration between UCLA’s experimental team and Caltech’s theory team in developing and understanding novel catalysts for renewable energy technologies, including fuel cells, hydrogen production, and CO2 reduction.

“This study exemplifies how our integrated experimental and theoretical efforts can yield unprecedented insights into nanostructure catalysis. By identifying the key intermediate, the research offers foundational insights for catalyst design, potentially transforming electrocatalyst development for renewable energy conversion and storage,” said Huang, Professor and Chair of Materials Science and Engineering at UCLA.

The implications for the energy industry are significant. More efficient Pt-based catalysts could lower costs and boost water electrolysis efficiency, accelerating green hydrogen production. This would enhance hydrogen fuel cell adoption in transportation and industry, reducing fossil fuel reliance and greenhouse gas emissions. As demand for sustainable energy solutions grows, such innovations will be crucial for the future of clean energy.

The UCLA research was supported by National Science Foundation and New Hydrogen Inc.

The Caltech research was supported from the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266.