Synthesis of spinel-type MCo2O4 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.