Synthesis of Spinel-Type MCo2O4 (M = Cu, Ni, Fe, Mn) Adsorbents and Their Performance in Trace H2S Capture for Cultural Heritage Preservation

Trace hydrogen sulfide (H ₂ S) causes irreversible deterioration of cultural relics even at low concentrations. To address the limitations of existing adsorbents in conservation environments, we developed Ni-doped Co ₃ O ₄ spinel nanosheets using a metal-organic framework precursor. The substitution of tetrahedral Co ²⁺ sites with Ni ²⁺ modulates the surface electronic structure, resulting in an adsorbed-to-lattice oxygen ratio O _ads /O _latt of 1.21. Density functional theory (DFT) calculations combined with experimental data indicate that these surface oxygen species promote electron transfer from H ₂ S and facilitate oxidative dissociation. The NiCo ₂ O ₄ material exhibits a saturation capacity of 4.2 mmol g ^-1 at 25 °C, compared to 2.0 mmol g ^-1 for commercial activated carbon, and maintains 92% capacity after ten regeneration cycles. Crucially, in accelerated aging environments, the material achieves near-total suppression of sulfidation on silver coupons and lead white pigments, demonstrating its potential as a high-efficiency safeguard for cultural heritage.