Phase-Restructured SnS2 Nanodots: Unlocking ORR Activity through Thermal Stress-Mediated Fracturing.

The production of electrocatalytically active materials from inert precursors through intricate engineering represents a frontier in sustainable energy research. The present study unveils a transformative thermal stress-mediated fracturing strategy to activate the oxygen reduction reaction (ORR) in SnS2, a material traditionally considered unsuitable for such electrocatalytic applications. By subjecting bulk SnS2 hexagonal plates to extreme thermal shock via rapid heating followed by instant quenching in liquid nitrogen, a simultaneous reduction in dimensionality and a critical 1T-to-1H phase transition has been achieved, yielding ultra-small 1H@1T-SnS2 nanodots (2-5 nm). High-resolution aberration-corrected STEM imaging reveals a restructured atomic lattice where the emergence of the 1H phase, coupled with plentiful edge sites, fundamentally reconfigures the electronic landscape. While the parent 1T-SnS2 follows an inefficient 2-electron pathway, the phase-restructured nanodots exhibit a robust 4-electron oxygen reduction mechanism. Theoretical insights from Density Functional Theory (DFT) confirm that the synergy between the 1H-phase transition and edge-site enrichment lowers the Gibbs free energy for intermediate adsorption, effectively "unlocking" the catalytic potential of SnS2. This work provides an erudite blueprint for the phase-and-size engineering of non-precious metal dichalcogenides, transmuting mundane semiconductors into high-performance electrocatalysts for the next generation of fuel cells and metal-air batteries.