Covalent sulfur–oxygen linkages enhanced the localized acidic environment coupled with the hydrogen spillover effect for boosting hydrogen evolution reaction kinetics

Abstract

The kinetics of electrode reactions are significantly influenced by the characteristics of the catalyst and the local reaction environment. Herein, we propose a strategy to achieve highly active electrocatalysts by designing a localized acidic environment to promote hydrogen spillover. By fabricating a CuFe₂O₄@CuFeS₂ heterojunction and forming covalent sulfur–oxygen (S–O) linkages between CuFe₂O₄ and CuFeS₂, we have successfully created an acidic environment and H* transport channels in alkaline electrolytes, leading to enhanced electrocatalytic hydrogen evolution performance. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) revealed the creation of a localized acidic environment with H₃O⁺ intermediates within the CuFe₂O₄ region in alkaline media, owing to the presence of electron-rich surface oxygen atoms at CuFe₂O₄@CuFeS₂ interfaces. These H₃O⁺ intermediates effectively reduced the energy barrier for water dissociation and supplied adequate hydrogen protons (H*), facilitating the migration of hydrogen spillover from CuFe₂O₄ to CuFeS₂. Meanwhile, theoretical calculations indicate that the covalent S–O bonds between CuFe₂O₄ and CuFeS₂ can serve as H* transport channels, which further facilitate the occurrence of hydrogen spillover. Consequently, the synergistic effect of the localized acidic environment coupled with hydrogen spillover significantly improves the reactivity of the hydrogen evolution reaction (HER).