Graphene/Hexagonal Boron Nitride Heterostructures for O2 Activation and Co Oxidation: Metal-Free Catalysts by Design

Pristine graphene and hexagonal boron nitride(h-BN) monolayers are chemically inert to oxygen, possessing limited catalytic activity towards O2 activation, entailing O2 dissociation energy barriers of 2.39 eV and 2.62 eV on pristine graphene (J. Appl. Phys.2012, 112, 104316) and h-BN monolayer (Phys. Chem. Chem. Phys.2012, 14, 5545). Herein, we present compelling computational evidence that graphene/h-BN heterostructures, successfully fabricated in the laboratory (Nature Nanotechnology 2013,8, 119), exhibit surprising O2 activation capability with significantly lowered O2 dissociation barriers. To gain deeper insights into the predicted high catalytic activities, we theoretically designed six graphene/h-BN heterostructures with different grain-domain interfaces and systematically investigated their catalytic activities toward O2 activation and CO-oxidation. Notably, we discover that O2 can be molecularly adsorbed and activated on electron-rich graphene/h-BN heterostructures. Furthermore, both electron-rich and electron-deficient graphene/h-BN heterostructures facilitate O2 dissociation with relatively low energy barriers (< 0.4 eV), whether starting from physisorbed or molecularly chemisorbed O2. Additionally, for 1B3N-GBN graphene/h-BN heterostructure, the computed rate-limiting step energy barrier of CO oxidation is approximately 0.67 eV. The high catalytic activities toward O2 dissociation stem from either accumulated electrons on the active atoms at the interfaces of electron-deficient heterostructures, or from electron richness and reduced work function for electron-rich heterostructures. Moreover, the high catalytic activities of graphene/h-BN heterostructures are insensitive to the patterns of BN-substitutes, enhancing their applicability and versatility. Hence, this novel class of metal-free 2D catalysts is not only cost effective but also could shows potential to rival the precious-group based catalysts (e.g., nanogold) for O2 activation or CO-oxidation.