Bimetallic AuPt/TiO<sub>2</sub>Catalysts for Direct Oxidation of Glucose and Gluconic Acid to Tartaric Acid in the Presence of Molecular O<sub>2</sub>
Mengyuan Liu, Xin Jin, Guangyu Zhang, Qi Xia, Linyi Lai, Jinyao Wang, Wenxiang Zhang, Yu Sun, Jie Ding, Hao Yan, Chaohe Yang
Abstract
Tartaric acid is an important industrial building block in the food and polymer industry. However, green manufacture of tartaric acid remains a grand challenge in this area. To date, chemical synthesis from nitric acid-facilitated glucose oxidation leads to only <10% yield with significant toxics as byproducts. We reported a one-pot aqueous-phase oxidation of glucose and gluconic acid using bimetallic AuPt/TiO2 catalysts in the presence of molecular O2, with ∼50% yield toward tartaric acid at 110 °C and 2 MPa. Structural characterization and density functional theory (DFT) calculation reveal that the lattice mismatch between fcc Pt and bcc Au induces the formation of twinned boundaries in nanoclusters and Jahn–Teller distortion in an electronic field. Such structural and electronic reconfiguration leads to enhanced σ-activation of the C–H bond competing with π–π electronic sharing of the C═O bond on the catalyst surface. As a result, both C–H (oxidation) and C–C (decarboxylation) bond cleavage reactions synergistically occur on the surface of bimetallic AuPt/TiO2 catalysts. Therefore, glucose and gluconic acid can be efficiently transformed into tartaric acid in a base-free medium. Lattice distortion-enhanced reconfiguration of the electronic field in Pt-based bimetallic nanocatalysts can be utilized in many other energy and environmental fields for catalyzing synergistic oxidation reactions.