An efficient electrocatalyst for oxygen reduction to water - boron nitride nanosheets decorated with small gold nanoparticles (∼5 nm) of narrow size distribution on gold substrate

Gold is known to be a poor electrocatalyst for oxygen reduction reaction (ORR) in acidic solution as oxygen is reduced to H2O2 by 2-electron process with high overpotential at a Au electrode. We found that the overpotential for ORR is decreased by the modification of the Au electrode with boron nitride nanosheet (BNNS), an insulator, but ORR still proceeds by 2-electron process. We have recently demonstrated that the decoration of BNNS by gold nanoparticles (AuNPs: 5-30 nm) opens a 4-electron ORR route to water, although only ca. 50% of oxygen is reduced to water. Here, we report that more than 80% of oxygen is reduced to water at the Au electrode modified by BNNS decorated with AuNPs of small size (ca. 5 nm) with narrow size distribution. Furthermore, the ORR overpotential is much less than that at the Au electrode modified by BNNS decorated with AuNPs of random size (5-30 nm) by 100-120 mV and is only 100 mV more than that at a Pt electrode.