Bottom-up sol-gel synthesis of 2D lead glycolate and oxide nanostructures towards electrochemical ozone production

Abstract

Despite extensive progress on two-dimensional (2D) materials, 2D lead oxides remain underexplored, limiting systematic structure-property studies. Here, we develop a bottom-up sol-gel synthesis route to 2D lead glycolate (PG) and oxide nanostructures via finely tuned hydrolysis-condensation of molecular metal alkoxides. The hydrolysis-condensation in ethylene glycol (EG), with controlled Pb-EG precursor/water and water/alcohol ratios, yields 2D-assembled nanoparticles, elongated nanostructures, and single-crystalline 2D hexagonal nanoplates. While calcination at 450 °C leads to a conversion of PG to tetragonal Pb3O4 with a significant collapse of 2D morphology, the introduction of a SiO2 overlayer can preserve the original 2D architecture of PG, affording 2D-assembled Pb3O4/SiO2 with minimal aggregation. The higher overpotential of 2D-assembled Pb3O4/SiO2, with a delayed current-onset potential, evidences its enhanced selectivity for electrochemical ozone production over oxygen evolution. This is further confirmed by a higher current density and a smaller Tafel slope in the high-potential region above ~2.8 V. KI-starch assay and UV-Vis spectroscopy confirm more efficient ozone generation by 2D-assembled Pb3O4/SiO2 compared to aggregated Pb3O4. This morphology-preserving route offers a general strategy for synthesizing structurally defined 2D lead oxide catalysts with enhanced performance.