Efficient HCHO oxidation at room temperature via maximizing catalytic sites in 2D coralloid δ-MnO2@GO

Airborne formaldehyde (HCHO) in indoor environments causes serious health problems and needs to be efficiently eliminated. However, the efficient and stable catalytic oxidation of HCHO can be hardly achieved at room temperature over transition metal oxides due to the limited exposure of active sites. Herein, δ-MnO2@GO catalysts were originally synthesized via a facile in situ growth of δ-MnO2 on the trace graphene oxide (GO) substrate (1%) and stably exhibited nearly 100% HCHO elimination at room temperature. δ-MnO2@GO showed the unique 2D coralloid structure with uniformly dispersed δ-MnO2 nanorod on planar-structured GO, which greatly enhanced the exposure of catalytic sites and mass transfer of reactants. The abundant surface reactive oxygen species (ROS) and hydroxyl (-OH) groups were rapidly generated from the activation of O2 and surface-adsorbed water over highly exposed catalytic sites. The ROS and -OH groups cooperated well cooperated to maintain the exceptional catalytic activity and stability towards HCHO degradation. In-situ DRIFTS results showed that catalytic HCHO oxidation predominantly follows the Langmuir-Hinshelwood (L-H) mechanism over the δ-MnO2@GO. This study presents a simple yet effective strategy for maximizing exposure to catalytic active sites and rational design of efficient catalysts for indoor HCHO elimination.