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: 5–30nm) 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. 5nm) 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 (5–30nm) by 100–120mV and is only 100mV more than that at a Pt electrode.