Synthesis of Mesoporous Carbon by Stabilization of the Nanoparticles Forming the Resorcinol/Formaldehyde Gels

CESAR. A. BARBERO; JUAN BALACH; MARIANO M. BRUNO; GABRIEL A. PLANES; M. CRISTINA MIRAS

Comprehensive Guide for Mesoporous Materials, Volume 1: Synthesis and Characterization.

Nova Science Publishers, Inc.

Lugar: New York; Año: 2015; p. 361 - 388

The reaction of resorcinol and formaldehyde, catalyzed by base, produce a porous gel formed by chain-like aggregates of resin nanoparticles. Conventional drying caused aggregation of the constituent nanoparticles, with collapse of the pores, producing a resin without open pores (xerogel). The pyrolysis of the resin produces a compact carbon. The usual way to avoid pore collapse is to avoid water evaporation and instead drying using supercritical fluids (aerogels), lyophilization (cryogels) or using low surface tension solvents (ambigels). In all cases, the procedures are complex and expensive, including solvent exchange and/or long curing steps. In this chapter we describe the use of different species (micelles, polyelectrolytes, fibers or nanoparticles) to stabilize the resin nanoparticles against aggregation during drying. In that way, porous dry resin can be produced by air drying without complex experimental steps. Pyrolysis of the dry porous resins produces porous carbons which are suitable for applications in energy storage (supercapacitors), water purification (deionizers), energy conversion (fuel cells) or catalysis. Moreover, the size and distribution of pores can be controlled by the concentration of soluble stabilizers. On the other hand, hierarchical porous carbons can be produced by hard templating the resin with silica nanoparticles or cellulose fibers. The materials are characterized and properties relevant to technological applications are measured.