Self-Reconstructed Spinel with Enhanced SO42− Adsorption and Highly Exposed Co3+ From Heterostructure Boosts Activity and Stability at High Current Density for Overall Water Splitting

Abstract

Developing overall water splitting non-noble metal electrocatalysts achieving long-term stability with high activity at industrial-grade current density remains challenging. Herein, a self-reconstruction strategy of Co₉S₈-Ni₃S₂/NCF is employed to fabricate Ni_xCo_3-xO₄-Ov-${\mathrm{SO}}_4^{2-}/\mathrm{NCF}$ in which partial Co is replaced by Ni in the structure. The reconstructed Ni_xCo_3-xO₄-Ov can enhance the adsorbing ability of ${\mathrm{SO}}_4^{2-}$ leached from the initial phase compared with Co spinel, achieving exceeding 1000-h oxygen evolution reaction (OER) and 600-h overall water splitting stability at 1000 mA cm⁻² with excellent activity. In situ Raman and X-ray photoelectron spectroscopy (XPS) results indicate that partial substitution of Ni for Co atoms enhances the ${\mathrm{SO}}_4^{2-}$ adsorption capacity on the reconstructed Ni_xCo_3-xO₄-Ov, facilitating the formation of high-density Co³⁺ active sites on (400) that expedited interfacial electron transfer at high current densities. Density functional theory (DFT) calculations reveal that the adsorption of leached ${\mathrm{SO}}_4^{2-}$ stabilizes surface oxygen vacancies and optimizes the adsorption energy of intermediates, thereby improving both stability and catalytic performance. The findings provide new insights into overcoming the activity-stability trade-off and contribute to the strategy for the design of electrocatalysts for long-term water splitting at industrial-grade current densities.