Green self-assembly of CuCe2(MoO4)4/montmorillonite-K10 nanocomposites; a promising solid-state hydrogen storage profile

Abstract

Rapid scale-up of the technologies for clean energy production, conversion and storage have been adopted by many countries in order to reduce demand for fossil fuels. Primary renewable energy such as solar, wind, and hydro are developed for energy production particularly for electricity generation. However, there are still some deficiencies in direct use of primary renewable energy sources; therefore, secondary energy sources (or carriers) have been recently established as clean energy sources. Hydrogen is a type of secondary energy sources with almost low density and light weight; therefore, it must be stored in the form of liquid or gas. The storage of hydrogen in the form of liquid requires very low temperature. Solid-state hydrogen storage on the surfaces of solids or within solids is a promising solution to above shortcomings for high-density energy storage. Herein, multi-layers solid-state materials with ability of hydrogen adsorption are presented, for the first time, including “mixed metal oxide (MMO) nanostructures” and “silicate layers”. The MMO is CuCe2(MoO4)4 nanostructures which synthesized via Pechini method in front of various chelating agents such as trimesic acid, maleic acid, succinic acid, and malonic acid, while the silicate layer is nanoclay montmorillonite K10. In this study, the experimental observations reveal a pure formation of CuCe2(MoO4)4 nanostructures in malonic acid at 500 °C, with almost regular nanosized morphology of 20–25 nm. The selected sample is then used for nanocomposite formation by dispersing the CuCe2(MoO4)4 nanostructures into the montmorillonite K10 solution. The final nanocomposites exhibit a superior electrochemical hydrogen storage performance, in terms of “maximum discharge capacity of ∼ 3750 mAh/g)” and “efficiency of about 70%” in an alkaline medium. It must be mentioned that though the maximum discharge capacity of the CuCe2(MoO4)4 nanostructures is higher than nanocomposites (for example ∼ 6000 mAh/g), but the efficiency (discharge/charge) is lower (∼48%). It can be emphasized that this nanocomposite can be applied as promising host in an electrochemical hydrogen storage system, which can meet the U.S. Department of Energy (DOE) hydrogen storage targets.