Synthesis and characteristics of carbon-SnO2 composite aerogel via two-step self-assembly approach

Abstract

Aerogels with unique hierarchical structure have attracted more and more attention in recent years. Especially, semiconductor aerogel, as one representative, is emerging owing to their controllable binding energy, bandgap, morphology, etc. In this work, a two-step self-assembly strategy of liquid phase was adopted to create carbon-mixed SnO2 gel, where SnO2 gel was self-assembled in a molecular route and then transformed into carbon-SnO2 gel at the second stage induced by interaction with the carbon resource (glucose) under hydrothermal condition. In this process, SnO2 colloids, rather than tin ions, could not only accelerate the carbonization of glucose molecules, but also help to build the cross-linking network of non-covalent bonding. Subsequently, freeze-drying was utilized to discharge the liquid from carbon-SnO2 gel to form aerogels. In addition, the evolution of hybrid carbon-mixed SnO2 aerogels during calcining at different temperature was also discussed. As carbon-containing structure blocked inside pores gradually grew into flaky carbon or was thermolyzed after calcination, previous microporous and mesoporous hierarchical structure was recovered and then SnO2-based composite aerogels were generated, even were reduced as Sn-based composite aerogels at 850 °C in nitrogen. As a result, hybrid Sn-based composite aerogels exhibited a higher BET surface area and good electrical conductivity (3 S/cm).