Replacing CTAB with Renewable-Origin Surfactants for the Synthesis of Mesoporous 8YSZ: Structural Integrity, Functional Validation, and Sustainability Assessment

Abstract

Cetyltrimethylammonium bromide (CTAB), a conventional structure-directing agent for mesoporous materials, is a petroleum-derived toxic compound whose removal requires energy-intensive multistep purification, increasing the environmental impact of the process. This study presents the sustainable synthesis of mesoporous 8 mol % yttria-stabilized zirconia (8YSZ) by replacing CTAB with glycerol (GLY) and glycerol monostearate (GMS), low-cost, renewable agents derived from the oleochemical industry. Raman spectroscopy, X-ray diffraction, electron microscopy, and N2 physisorption confirm the formation of fully cubic fluorite 8YSZ with mesoporous frameworks of interconnected nanocrystals, which exhibit appropriate macroporosity after high-temperature sintering. Ionic conductivity measurements, corrected for porosity, tortuosity, and constrictivity, demonstrate that scaffolds derived from renewable surfactants retain intrinsic oxygen-ion conduction equivalent to the CTAB reference and consistent with literature values for dense 8YSZ. A quantitative sustainability assessment shows that the renewable route reduces process mass intensity by up to 89% (from ∼710 to 78–81), energy intensity by 73% (from 3.87 to 1.03 kWh g–1), and production costs by up to 60%, while maintaining structural integrity in batches up to 10 g. These findings establish renewable surfactant substitution as a viable, scalable strategy for greener synthesis of functional porous ceramics, with direct relevance to electrochemical devices, catalyst substrates, and separation membranes.