Inorganic cryogels for energy saving and conversion

Abstract

Cryogels are usually obtained by freezing and thawing or freeze drying of gels and residues. Essential morphological features of the cryogels are bimodal pore size distribution, nanosize of the primary particles (crystallites) and their low agglomeration. Widely used for a decades in the polymer science and technology, cryogels find now a growing number of applications in the electroceramic materials. Freeze casting technique based on the freeze gelation effect is proved to be useful forming method in the production of complex-shaped SiO2-containing electroceramics. Directed modification of the micromorphology by using solvent exchange schemes allows to obtain SiO2 cryogel monoliths with density ≤ 0.05 g cm−3 and specific surface area 700–800 m2 g−1 suitable for cryogenic thermal insulation of the superconducting devices. Excellent electrocatalytic activity of the macro/mesoporous PtRu/C cryogels in the methanol oxidation reaction makes them perspective anode materials of direct methanol fuel cells. Application of the cryogel-derived starting powders promoted substantial reduction of the sintering temperatures for a number of electroceramic materials. MnO2- and V2O5-based cryogels are efficient cathode materials for secondary lithium batteries with specific capacity up to 300 mAh g−1. Recent studies demonstrated also a feasibility of cryochemical approaches to the synthesis of complex oxide-based nanocrystalline electrode materials for electrochemical supercapacitors with high specific capacity at current densities up to 50 mA cm−2.