Tuning oxygen vacancy and basicity of CeO2 via morphology engineering for the coproduction of acetol and lactic acid from rhamnose

The conversion of Enteromorpha prolifera -derived rhamnose to value-added chemicals was investigated over a panel of metal oxide catalysts under N 2 atmosphere. The catalytic performance correlated strongly with the surface acid-base properties, oxygen vacancy concentration, and electrophilicity of the oxides. Among those screened, CeO 2 exhibited the highest activity and selectivity for the coproduction of acetol and lactic acid. This motivated a systematic investigation into how the acid-base properties and oxygen vacancy concentration of CeO 2 can be modulated by morphological control. To this end, CeO 2 nanoparticles (CeO 2 -N), nanocubes (CeO 2 -C), nanorods (CeO 2 -R), and nanospheres (CeO 2 -S) were synthesized and characterized. Combined experimental and characterization results revealed CeO 2 -R as the most active catalyst, attributed to its pronounced electrophilicity, moderate oxygen vacancy concentration (52.3% by XPS), and the highest density of basic sites (0.66 mmol/g by CO 2 -TPD), achieving a total yield of 64.3 C-mol% for acetol and lactic acid (180 ℃, 1 h, 100 mg CeO 2 -R). This unique combination of surface properties facilitated a cascade reaction pathway involving: (i) ring-opening and isomerization of rhamnose, followed by (ii) selective C3-C4 bond cleavage to yield key C 3 intermediates (1,3-dihydroxyacetone (DHA) and lacticaldehyde). Kinetic study revealed that strong basic sites drive the conversion of DHA to lactic acid via a dehydration-1,2-hydride shift, while promoting lacticaldehyde isomerization to acetol. These pathways are synergistically enhanced by moderate oxygen vacancy and strong basic sites, which stabilize key intermediates. This work establishes a morphology-engineering strategy to rationally tune the oxygen vacancy and basicity of CeO 2 catalysts, offering new insights into the design of defect-controlled oxides for biomass valorization. • First valorization of E. prolifera -derived rhamnose to acetol and lactic acid without H 2 . • CeO 2 nanorods achieve 64.3C-mol% yield via morphology-controlled defect engineering. • Moderate oxygen vacancies + high basicity enable selective C3-C4 bond cleavage. • DHA and lacticaldehyde confirmed as key intermediates via control experiments.