Boron Nitride - Gold As a Novel Electrocatalyst for Oxygen Reduction Reaction
DFT calculations show that the band gap of free h-BN monolayer is 4.6 eV but a slight protrusion of the unoccupied BN states towards the Fermi level is observed if BN is supported on Au(111) due to the BN-Au interaction. Theoretically predicted metastable configuration of O2 on h-BN/Au(111), which can serve as precursors for ORR, and free energy diagrams for ORR on h-BN/Au(111) via two- and four-electron pathways show that ORR to H2O2 is possible at this electrode. Electrocatalytic activities of various types of h-BN, i.e., spin coated BN nanotube (BNNT) and BN nanosheet (BNNS) and sputter deposited BN, on Au electrodes as well as those of BNNS modified glassy carbon (GC) and Pt electrodes for oxygen reduction reaction (ORR) were examined in O2 saturated 0.5M H2SO4solution. The overpotential for ORR at Au electrode was reduced by ca. 100, ca. 270, and ca.150 mV by spin coating of the dispersion of BNNT and liquid exfoliated BNNS, and sputter deposition of BN, respectively, proving the theoretical prediction. The reason why the highest activity was obtained by the BNNS modification is attributed to the presence of B-and/or N-edge structures. While the BNNS modification was very effective to improve ORR activity at Au electrode, it has no and negative effects at GC and Pt electrodes, respectively, confirming the important role of BN-Au interaction for ORR activity enhancement.
XPS measurements were carried out to show the modulation of electronic structure and several attempts are made to increase the BN-Au interaction so that electrocatalytic activity can be enhanced.
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