Kinetics of Hydrogen Generation from Oxidation of Hydrogenated Silicon Nanocrystals in Aqueous Solutions.

Gauhar Mussabek,Sergei V. Litvinenko,Anton I. Manilov,Sergii Tutashkonko,Sergei A. Alekseev,Tetyana Nychyporuk,Gulshat Amirkhanova,Valeriy A. Skryshevsky,Vladimir Lysenko,Yerkin Shabdan

doi:10.3390/nano10071413

Abstract

Hydrogen generation rate is one of the most important parameters which must be considered for the development of engineering solutions in the field of hydrogen energy applications. In this paper, the kinetics of hydrogen generation from oxidation of hydrogenated porous silicon nanopowders in water are analyzed in detail. The splitting of the Si-H bonds of the nanopowders and water molecules during the oxidation reaction results in powerful hydrogen generation. The described technology is shown to be perfectly tunable and allows us to manage the kinetics by: (i) varying size distribution and porosity of silicon nanoparticles; (ii) chemical composition of oxidizing solutions; (iii) ambient temperature. In particular, hydrogen release below 0 °C is one of the significant advantages of such a technological way of performing hydrogen generation.

Highlights

Hydrogen and fuel cell technologies have strong potential to play a significant role in new energy systems [1]
The water diffusion coefficient increases at the higher temperature (+23 ◦C) and it automatically leads to the enhanced hydrogen generation kinetics, as well as to the much higher quantity of hydrogen (6.7% mass) generated at the end of the reaction between the silicon nanopowder and water/ethanol mixture
Hydrogen generation rate is one of the most important parameters which must be considered for the design of engineering solutions for hydrogen energy applications

Summary

Introduction

Hydrogen and fuel cell technologies have strong potential to play a significant role in new energy systems [1]. In strong contrast to oil and molecular hydrogen, the transport and storage of silicon are free from potential hazards and require a simple infrastructure similar to that requested for coal Whereas the latter material is converted to carbon dioxide, silicon involved in hydrogen production is transformed in sand. The maximum specific surface of nanoporous silicon can reach the value of 800 m2/g, while the content of hydrogen chemically bound on the surface can be as high as 60 mmol of atomic H per gram of porous Si, corresponding to the H/Si ratio ~1.8 or to the 6% mass of H [44] The presence of this surface hydrogen can increase the output volume of H2, which releases in the reaction of porous silicon nanoparticles with water by 1.5 times [54]. This is especially evident for the porous nanostructures, where a higher oxidation degree of nanosilicon can result in the blocking of the nanopores with silicon oxide [64]

Hydrogen Generation from Oxidation of Porous Silicon Nanopowders in Water

Formation of PSi Nanopowders

Structural Characterization of PSi Nanopowders

Findings

Conclusions