Coproduction of Glyceric Acid and Glycolic Acid from Biomass-Based Sugars over a Ru/Co3O4 Catalyst

α-Hydroxyl acid production from biomass has emerged as a promising approach for biomass valorization but remains a long-standing challenge due to limited productivity. Herein, we established an innovative strategy for the coproduction of glyceric and glycolic acids from pentose feedstocks. Ru/Co3O4 catalyst, possessing tunable Run+/Ru0 ratio and abundant oxygen vacancy, was found to promote the total yield of glyceric acid and glycolic acid (up to 65.9 C-mol % with a ∼1:1 molar ratio based on the initial carbon in the feedstock, the highest value among the state-of-the-art advances) at a mild temperature (70 °C). The results of the isotopic tracing experiments confirmed that xylose underwent C2–C3 cleavage, yielding glyceraldehyde and glycolaldehyde intermediates, which could be oxidized to produce glyceric acid and glycolic acid, respectively. In combination with density functional theory (DFT) calculations, it was revealed that Run+ and Ru0 with an appropriate Run+/Ru0 ratio, in addition to oxygen vacancies, made a pronounced cooperative contribution to achieve complicated cascade reactions. Run+ was proven to be more favorable for xylose adsorption via the interaction with the −C═O, thereby accelerating the ring-opening reaction and C2–C3 cleavage, while Ru0, together with oxygen vacancies, mainly contributed to the activation of O2 to produce active oxygen species that facilitated the immediate oxidation of intermediates. The results of this work may provide useful insights into catalyst design and potential directions to maximize carbon utilization in biomass valorization.