Influence of Ti as an oxyphilic metal atom doped in Ni3S2 system on catalytic performance and mechanism

Among non-precious metal catalysts, non-oxide materials often undergo surface oxidation under high-anodic potentials during the oxygen evolution reaction (OER), forming hydroxyl oxides or oxyhydroxides that serve as the true active phases with intrinsically higher activity. However, this structural transformation is frequently accompanied by surface relaxation, lattice distortion, or even partial collapse, leading to progressive degradation of catalytic stability, particularly under high-current-density operation, where long-term structural integrity is severely challenged. Enhancing the operational stability of such non-oxide catalysts is therefore a critical and unresolved challenge. In this work, we rationally doped Ti atoms into the Ni 3 S 2 lattice via a one-step solvothermal synthesis. Ti incorporation introduces low-coordinated metal sites that function as highly dispersed, atomically efficient active centers. These sites promote rapid deprotonation kinetics and lower the energetic barrier for O O bond formation, thereby significantly boosting intrinsic OER activity. The resulting catalyst delivers an overpotential of only 238 mV to achieve a current density of 10 mA cm −2 in 1 M KOH. Crucially, during electrocatalysis, the oxyphilic Ti dopants undergo controlled, sacrificial dissolution and act as “voltage buffers” that mitigate lattice strain and suppress irreversible oxidation of the Ni S framework under high anodic bias. This dynamic stabilization mechanism preserves the structural coherence of the catalyst, enabling stable operation at relevant current densities for over 400 h. Density functional theory (DFT) calculations corroborate the mechanism that confirms the preferential adsorption of OH* and O* intermediates at bridge and top sites associated with low-coordinated Ni atoms, and quantitatively reveal how Ti doping modulates the adsorption strength and coverage of key intermediates across applied potentials. Collectively, this study demonstrates a scalable, rational design strategy integrating targeted dopant selection, mechanistic understanding, and operando stabilization that advances non-oxide, non-noble metal catalysts toward practical water electrolysis applications.