Manipulating d‑Band\nCenter of Nickel by Single-Iodine-Atom\nStrategy for Boosted Alkaline Hydrogen Evolution Reaction

Ni-based electrocatalysts have been predicted as highly\npotential\ncandidates for hydrogen evolution reaction (HER); however, their applicability\nis hindered by an unfavorable d-band energy level (<i>E</i><sub>d</sub>). Moreover, precise d-band structural engineering of\nNi-based materials is deterred by appropriative synthesis methods\nand experimental characterization. Herein, we meticulously synthesize\na special single-iodine-atom structure (I–Ni@C) and characterize\nthe <i>E</i><sub>d</sub> manipulation via resonant inelastic\nX-ray scattering (RIXS) spectroscopy to fill this gap. The complex\ncatalytic mechanism has been elucidated via synchrotron radiation-based\nmultitechniques (SRMS) including X-ray absorption fine structure (XAFS),\nin situ synchrotron radiation-based Fourier transform infrared (SR-FTIR)\nspectroscopy, and near ambient pressure X-ray photoelectron spectroscopy\n(NAP-XPS). In particular, RIXS is innovatively applied to reveal the\nprecise regulation of Ni <i>E</i><sub>d</sub> of I–Ni@C.\nConsequently, the role of such single-iodine-atom strategy is confirmed\nto not only facilitate the moderate <i>E</i><sub>d</sub> of the Ni site for balancing the adsorption/desorption capacities\nof key intermediates but also act as a bridge to enhance the electronic\ninteraction between Ni and the carbon shell for forming a localized\npolarized electric field conducive to H<sub>2</sub>O dissociation.\nAs a result, I–Ni@C exhibits an enhanced alkaline hydrogen\nevolution performance with an overpotential of 78 mV at 10 mA/cm<sup>2</sup> and superior stability, surpassing the majority of the reported\nNi-based catalysts. Overall, this study has managed to successfully\ntailor the d-band center of materials from the SRMS perspective, which\nhas crucial implications for nanotechnology, chemistry, catalysis,\nand other fields.