Porous Ceramics Prepared from 3D Printed Pickering Emulsions as Gold Nanoparticle Supports for Reduction Reactions

We present a facile method to fabricate a porous ceramic material by combining Pickering emulsion templating and direct ink writing-based three-dimensional (3D) printing. The Pickering emulsions stabilized by a binary mixture of fumed oxide particles, fractal-like aggregates of nanospheres, and polyelectrolytes were used as ink for direct ink writing. The ability of particle-polyelectrolyte complexes to adsorb at the oil-water interface was exploited for the design of printable emulsions. A control over the microstructure and rheology of the Pickering emulsion was modulated by tuning the emulsion formulation parameters such as the aqueous phase pH and concentration. The optimal conditions for the successful 3D printing of designs with excellent shape retention and structural integrity were identified by combining 3D printing experiments and detailed rheological studies. The grid-like architecture produced by 3D printing of optimal formulation was further dried and sintered to prepare an emulsion-templated porous TiO2 ceramic. The microstructure and pore characteristics of the resultant ceramic were investigated. Finally, the use of this porous ceramic as a support for immobilizing gold nanoparticles on the surface of the porous ceramic for application in catalysis was demonstrated; as an application, the effectiveness of this gold nanoparticle-loaded porous support was illustrated by harnessing its catalytic activity for efficient reduction of 4-nitrophenol, a common chemical pollutant in wastewater. The proposed Pickering emulsion-based ink system stabilized by fractal-like aggregates of TiO2 nanoparticles offers great flexibility in terms of 3D shaping and microstructure control and has good potential for developing functional ceramics of hierarchically porous structures for various applications.

Automated summary

This study presents a facile method that combines Pickering emulsion templating and direct ink writing-based 3D printing to fabricate porous ceramic materials. The control over the microstructure and rheology of the Pickering emulsion ink was achieved by tuning the emulsion formulation parameters. The resulting emulsion-templated porous TiO2 ceramic showed potential for various applications, including catalysis.