Ketal Protection of Glycerol for Selective Electrosynthesis of Glyceric Acid in Highly Alkaline Media

Electrocatalytic glycerol oxidation represents a sustainable route for glycerol valorization, yet high selectivity toward glyceric acid (GLA) remains challenging on non-noble-metal catalysts due to competing C─C bond cleavage and complex oxidation pathways. Herein, we introduce solketal, a ketal-protected glycerol derivative, to steer reaction selectivity. Its rigid five-membered ketal structure selectively exposes the primary hydroxyl group while shielding vicinal diols, thereby enforcing site-selective oxidation and suppressing C-C scission. Using a non-noble Cu₃Mo₂O₉ catalyst in 6.0 M KOH with 0.2 M solketal, the system achieves a record-high GLA selectivity of 90.1% with a production rate of 675.45 µmol cm^-2 h^-1 at 1.40 V versus RHE, reaching ∼95% substrate conversion within 5 h and maintaining stable operation over 100 h. Mechanistic investigations reveal that highly alkaline conditions promote solketal deprotonation to reactive alkoxide species, weaken the C_α─H bond to accelerate dehydrogenation kinetics, and mitigate local interfacial acidification, thus stabilizing the ketal-protected intermediate and suppressing side reactions. Furthermore, practical feasibility is demonstrated through integrated upstream solketal synthesis (90% yield, 99% purity) and downstream GLA isolation (99% purity). This work establishes a substrate-protection strategy for steering reaction pathways, offering new insights into the selective conversion of biomass-derived polyols into value-added oxygenates.