Hexagonal La2 O3 Nanocrystals Chemically Coupled with Nitrogen-Doped Porous Carbon as Efficient Catalysts for the Oxygen Reduction Reaction.

The construction of nano-scale hybrid materials with a smart interfacial structure, established by using rare earth oxides and carbon as building blocks, is essential for the development of economical and efficient catalysts for oxygen reduction reactions (ORRs). In this work, hexagonal La2 O3 nanocrystals on a nitrogen-doped porous carbon (NPC) derived from crop radish, served as building bricks, are prepared by chemical precipitation and then calcination at elevated temperatures. The obtained La2 O3 /NPC hybrid exhibits a very high ORR activity with a half-wave potential of 0.90 V, exceeding that of commercial Pt/C (0.83 V). Both DFT theoretical and experimental results have verified that the significantly enhanced catalytic performance is ascribed to the formation of the C-O-La covalent bonds between carbon and La2 O3 . Through the covalent bonds, electrons can transfer from the carbon to La2 O3 and occupy the unfilled eg orbital of the La2 O3 phase. This results in the accelerated adsorption of active oxygen and the facilitated desorption of the surface hydroxides (OHad - ), thereby promoting the ORR over the catalyst.