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 ceria-based 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.