![iridium metal xps iridium metal xps](https://tiimg.tistatic.com/fp/1/006/861/rare-precious-iridium-metal-powder-357.jpg)
Herein, we report a facile and scalable strategy to fabricate a low mass loading but high surface distribution density Ir SAC by anchoring on the Ni (3-x)Fe xS 2 (Ir 1/NFS) nanosheet arrays via a two-step electrochemical method. Another major challenge in the fundamental science of SACs is to enhance the surface distribution density of active sites on the outer surface of substrates, rather than embedded inside the bulk materials 28, 38. Despite these endeavors in developing suitable substrates for OER catalysts 17, 36, 37, the fundamental understanding of the interaction between the substrate and the supported isolated atoms is still illusive 38, 39, 40. Various substrate materials have been attempted to maximize the mass activity of previous metals 31, 32, 33, 34, 35. The interaction between individual precious metal atoms and support substrate plays essential roles in modulating the microenvironment of active sites and consequently improves their activity and durability 28, 29, 30.
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It has been proved that the utilization of SACs could significantly improve the intrinsic activity of precious metal elements for the OER process and result in high mass activity 24, 26, 27. Recently, tremendous efforts have been devoted to developing efficient SACs for suppressing the OER overpotentials and improving the reaction kinetics for electrochemical water splitting 22, 23, 24, 25. Single-atom catalysts (SACs) provide a promising option to significantly reduce the utilization amount of precious metal catalysts by maximizing the atom-efficiency of precious metal elements in catalyst materials 16, 17, 18, 19, 20, 21. The utilization of precious metal catalysts significantly impairs the cost competitiveness of hydrogen production via electrochemical water splitting in comparison with other conventional hydrogen production technologies from the steam reforming process 12, thus hindering the wide deployment of the electrolytic hydrogen production technology in the future 13, 14, 15. So far, the catalysts for OER need to utilize precious metals, such as iridium (Ir) and ruthenium (Ru), to suppress the overpential during the water electrolysis process 11. Thus, tremendous efforts have been made to improve the OER performance 10, thus achieving high-efficiency electrolysis for cost-effective hydrogen energy in alkaline electrolyzer.
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However, their catalytic performance remains far from satisfactory for the cost competiveness of hydrogen production. The commercial electrocatalysts used for water oxidaton in alkaline electrolyzer are Ni-based catalysts 9. Especially, the OER reaction involves a four-electron process which suffers from ten times higher overpotentials than that of HER, making it a bottleneck process in the overall water electrolysis system 4, 8. However, the sluggish kinetics of water electrolysis results in high overpotentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) 4, 5, thus significantly sacrificing the energy efficiency and increasing the hydrogen production cost 6, 7. Similar content being viewed by othersĮlectrochemical water splitting is considered as a sustainable option for large-scale hydrogen production by using renewable energy, such as solar, wind and hydropower 1, 2, 3. This work represents a promising strategy to fabricate high surface distribution density single-atom catalysts with high activity and durability for electrochemical water splitting. First-principles calculations reveal that the electronic structures of Ir atoms are significantly regulated by the sulfide substrate, endowing an energetically favorable reaction pathway. At the same time, the Ir 1/NFS catalyst exhibits a high stability performance, reaching a lifespan up to 350 hours at a current density of 100 mA cm −2. The Ir 1/NFS catalyst offers a low overpotential of ~170 mV at a current density of 10 mA cm −2 and a high turnover frequency of 9.85 s −1 at an overpotential of 300 mV in 1.0 M KOH solution. Herein, we present an approach to fabricate a high surface distribution density of iridium (Ir) SAC on nickel-iron sulfide nanosheet arrays substrate (Ir 1/NFS), which delivers a high water oxidation activity. However, it is still a challenge to enhance the intrinsic and specific activity of SACs. Single-atom catalysts (SACs) have attracted tremendous research interests in various energy-related fields because of their high activity, selectivity and 100% atom utilization.