Oxygen defect engineering in Pt/CeO2 catalyst for promoted selective oxidation of HMF to FDCA

Oxygen vacancies play an important role in the oxidation of biomass-derived alcohols and aldehydes using ceriabased catalysts. In this study, a highly oxygen vacancy-defective Pt/H-CeO2 catalyst was synthesized by a straightforward strategy that involved the control of the addition of ascorbic acid and nitric acid. The addition of ascorbic acid, which acted as a pore-forming agent, promoted the hydrolysis, crystallization, and subsequent growth of Ce precursor salt, resulting in the synthesis of H-CeO2 with abundant oxygen vacancy defects and a porous thin sheet-like morphology. However, the addition of nitric acid significantly inhibited the generation of oxygen vacancy defects. The obtained H-CeO2 exhibited significantly increased oxygen vacancy content, active oxygen species, and specific surface area compared with CeO2 with lower oxygen vacancy defects (L-CeO2). These remarkable features led to enhanced catalytic activity of Pt/H-CeO2 for the oxidation of 5-hydroxymethylfurfural (HMF) compared with Pt/L-CeO2. This can be mainly attributed to the enhanced adsorption and activation of O2 molecules by abundant oxygen vacancies, allowing more active oxygen species to participate in the dehydrogenation of HMF. This work provides an example of oxygen defect engineering for ceria-based catalysts to boost the catalytic selective oxidation performance.