Theoretical and Experimental Studies on Electrocatalytic Activities of Boron Nitride

Abstract

Oxygen reduction reaction (ORR) is one of the most important processes in fuel cells as well as in biological system. Pt based electrocatalyst is the most prominent ORR catalyst showing low over potential. Major challenges to commercialize the Pt based electrocatalyst are its high cost, less abundance, and still sluggish kinetics. These problems can be addressed by using metal-free carbon materials doped with various elements such as N and B. N- and B-doped carbon materials have been demonstrated to be effective metal free ORR catalyst. Therefore, one may expect that the consecutive substitution of carbon atoms in graphene by B- and N-atoms will result in an increase of ORR activity. In extreme case, if all the carbon atoms in graphene are substituted by B- and N-atoms, hexagonal boron nitride (h-BN) monolayer, which is an insulator with a wide band gap (˜5.8eV), can be obtained. Theoretical investigations show that atomically thin h-BN becomes semiconducting if some defects are introduced or it is placed on metal substrates and may acts as electrocatalyst for ORR.1, 2 Here, we studied the electrocatalytic behavior of BN of several shapes such as nanotube and nanosheets (BNNS) supported on Au toward ORR by using typical three electrode rotating disk electrode (RDE) in O2 saturated 0.5M H2SO4solution. The overpotential for ORR at Au electrode was reduced in all cases, confirming the electrocatalytic activity of BN, but the most significant effect was observed when BNNS was used as an electrocatalyst where ca. 280 mV reduction of overpotential was achieved.