Enhanced Thermal Stability and Oxygen Activation of Electrostatically Assembled Single‐Layer MnO 2 for Thermocatalysis and Single‐Atom Catalysis

2D materials-supported single-atom catalysts are of considerable interest in heterogeneous catalysis due to their unique geometric and electronic structures. However, most of the reported catalytic reactions over these catalysts are hitherto limited to electrocatalysis, photocatalysis, and other reactions operated under modest conditions. The compromised thermal stabilities of 2D materials and single atoms, in comparison to their 3D bulk counterparts, limit a proper evaluation of their catalytic capabilities in thermocatalysis. Herein, through cation exchange and electrostatic attraction, single-layer MnO₂ nanosheets wrapping around SiO₂ nanospheres with a 2D/3D structure show enhanced thermal stability at temperatures even higher than the phase-transition temperature of the bulk. Therefore, evaluating the thermocatalytic performance of single-layer MnO₂ nanosheets is made possible. With adequate band structure and stability, the MnO₂ nanosheets over SiO₂ also function well as a support for photochemically synthesizing atomically dispersed Pd catalysts. The yielded 0D/2D/3D structure is thermally stable for the catalytic oxidation reaction of CO. Overall, a potentially universal strategy to stabilize 2D materials for thermocatalysis is reported, which would contribute to both material science and molecular science.