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Enhanced Interactions between Gold and MnO2 Nanowires for Water Oxidation: A Comparison of Different Chemical and Physical Preparation Methods

Zhang, Haojie, Lin, Chao, Du, Fuping, Zhao, Yonghui, Gao, Peng, Chen, Hao, Jiao, Zheng, Li, Xiaopeng, Zhao, Tiejun, Sun, Yuhan
ACS sustainable chemistry 2015 v.3 no.9 pp. 2049-2057
gold, nanogold, X-ray photoelectron spectroscopy, hydroxyl radicals, sodium hydroxide, manganese dioxide, nanocomposites, palladium, nanowires, urea, electrolysis, hydrogen, oxidation, oxygen production, oxygen
Oxygen evolution reaction (OER) has been considered as the bottleneck step in water electrolysis to simultaneously produce hydrogen and oxygen. The earth abundant first-row metal oxides such as manganese oxide have been found very active after anchoring nanoparticular noble metals such as Au, Pd and Pt onto its surface. Recent reports have demonstrated that Au can increase the turnover frequency (TOF) of MnOₓ more than 10 times for the OER due to the unique local interaction between Au and MnOₓ. Here, we conducted a detailed comparative study of different preparation methods on the OER activity of Au/MnO₂ nanocomposites, including physical sputtering (PS), deposition–precipitation with urea (DPU), DP with NaOH (DPN) and deposition–reduction (DR) with NaBH₄. Through carefully controlling the preparation conditions, we find chemical preparation methods (i.e., DPU and DPN) can achieve uniform growth of monodispersed Au nanoparticles on MnO₂ nanowires (Au/MnO₂) same as sputtering; moreover, the as-prepared Au–MnO₂ by DPU and DPN shows stronger interaction than that by sputtering, thereby achieving higher OER performance. Delicate chemical valence change and conductivity improvement induced by such interaction are further quantified by conventional XPS, resistivity and impedance measurements.