Efficient production of H2O2 on Au/WO3 under visible light and the influencing factors

Production of H2O2 via a more economic, green and safe way is challenging. In this work, we report an efficient production of H2O2 from oxygen reduction reaction (ORR) in aqueous solution over a modified WO3 with Au nanoparticles. Under visible light at wavelengths longer than 420 nm for 5 h, H2O2 measured from WO3 and Au/WO3 were 1.07, and 177 μM, respectively. On addition of methanol, H2O2 obtained from WO3, Au/WO3, and Au/SiO2 were 8.55, 544, and 0.36 μM, respectively. Photoluminescence and electrochemical measurement revealed that there was an interfacial electron transfer from the excited WO3 to Au, followed by two-electron reduction of O2 on Au sites. Under visible light at wavelengths longer than 535 nm, interestingly, H2O2 was also produced from Au/WO3 (39 μM at 5 h), while the photocurrent of water oxidation on Au/WO3 was much larger than those on Au/SiO2 and WO3. Clearly, there is also an interfacial electron transfer from the plasmonic Au to WO3, followed by ORR to H2O2, but such a process fails when WO3 is excited. However, the production of H2O2 on Au/WO3 was determined by several factors, including Au content, light absorption, and particle size. A maximum H2O2 was observed at an initial pH 3.0 from 0.35 wt% Au/WO3, prepared at 400 °C. Moreover, at the same loading on WO3, Au was more efficient than Pd, Ag, Pt, Ni, Cu, and Co, while at the same Au loading, WO3 was more efficient than BiVO4 and Bi2WO6. The superior performance of Au/WO3 is mainly due to its ability to undergo selective ORR to H2O2, and to release protons into aqueous solution protecting H2O2 from decomposition.