Sulfur-vacancy engineering of Co₉S_8-x/Ti₃C₂T_x-MXene catalyst for efficient oxygen evolution reaction

Integrating conductive supports and modulating electronic structures are widely recognized as effective strategies for improving the catalytic performance of transition metal sulfides. This study demonstrates the simultaneous integration of Co₉S₈ with two-dimensional Ti₃C₂T_x-MXene and the introduction of sulfur vacancies (S_v) in Co₉S₈ through a straightforward sintering process followed by plasma treatment, culminating in the formation of the Co₉S_8-x/Ti₃C₂T_x composite. Characterization results demonstrate that the Ti₃C₂T_x support significantly improves electrical conductivity and promotes the uniform dispersion of Co₉S₈ nanoparticles. Experimental and theoretical analyses reveal that the introduction of S_v induces charge redistribution and optimizes the adsorption of reaction intermediates. The obtained Co₉S_8-x/Ti₃C₂T_x electrode exhibits superior oxygen evolution reaction (OER) performance, achieving an overpotential of 286 mV at a current density of 10 mA cm^-2 and a Tafel slope of 76 mV dec^-1, outperforming other counterparts and approaching the catalytic performance of commercial RuO₂ catalyst. Furthermore, it demonstrates exceptional stability, with a potential shift of only 18 mV during a durability test exceeding 13 h. As an anodic catalyst for water splitting, the Co₉S_8-x/Ti₃C₂T_x electrode achieves a low overpotential of 330 mV, highlighting its potential for practical water electrolysis applications. This study offers valuable insights into the design and development of advanced transition metal sulfide-based OER catalysts.