Methanobactin-mediated synthesis of bimetallic Au-Pd/Al₂O₃ toward an efficient catalyst for glucose oxidation

A green bioreductive approach with methanobactin was adopted to fabricate bimetallic Au-Pd/Al₂O₃ catalysts for solvent-free oxidation of glucose to gluconic acid with H₂O₂ at atmospheric pressure. The catalyst was characterised by diffuse reflectance UV-vis spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques to understand synergistic interactions between Au and Pd. Effects of Au to Pd molar ratio on the catalytic activity of Au-Pd/Al₂O₃ were investigated. The Au-Pd/Al₂O₃ catalyst with Au/Pd molar ratio of 0.8:0.2 exhibited excellent catalytic performance. With the catalyst, the oxidation activities of glucose to gluconic acid 2856 mmol min^-1 g^-1 and selectivity 99.6% were attained at 323 K with H₂O₂. The results indicated the activity and selectivity was affected by the ratio of Au/Pd on the Al₂O₃. The formation of Au_0.8Pd_0.2/Al₂O₃ was favourable for the catalytic reaction.