Selective oxidation of glucose to gluconic acid by bimetallic catalysts

Selective aerobic oxidation of glucose to gluconic acid under alkali-free aqueous conditions is constrained by inefficient Pt utilization, particle aggregation, and poorly controlled metal-oxide interfaces. Herein, we develop a urea-assisted solvothermal strategy that integrates oxide-support screening, interfacial electronic regulation, and hierarchical pore engineering in Pt/MOx catalysts. Among eight oxide supports, Pt/NiO-U exhibited the highest activity. Comparative synthesis using NaOH and Na2CO3 decoupled the structural role of urea from simple alkalinity, revealing that urea acts simultaneously as a slow-release pH regulator and a source of nitrogen-containing surface species. This multifunctional regulation generated highly dispersed Pt nanoparticles with an average diameter of 2.89 nm, modified the electronic environment of the Pt-NiO interface, and increased the availability of reactive surface oxygen species. N2 sorption further indicated a mesopore-dominated micro-meso-macroporous hierarchy spanning 1.72–148.55 nm, thereby coupling nanoscale active-site exposure with multiscale mass transport. At 100 °C under 1 MPa O2, Pt/NiO-U achieved 100% glucose conversion and a gluconic acid yield of 92.5% without added soluble alkali, markedly outperforming the NaOH- and Na2CO3-derived counterparts, which afforded yields of only 45.6% and 50.4%, respectively. Complete conversion with an 85.2% gluconic acid yield was also obtained at 80 °C within 1 h. The catalyst maintained complete conversion over five cycles, with a fifth-cycle yield of 79.3% and Pt and Ni leaching below 0.1%. These findings establish urea-assisted Pt-NiO interface engineering as a unified strategy for coordinating active-site dispersion, oxygen activation, and hierarchical mass transport in selective biomass oxidation.