Despite the hype surrounding hydrogen energy, the commercial use of H2 continues to be hampered by difficulties associated with its storage and transportation. At the industrial level, none of the available materials are capable of containing large quantities of hydrogen and releasing it easily.
A possible solution has been offered by scientists from the Institute of Solid State Physics RAS, who have suggested hydrogen could be stored in hollow nanospheres made of silicon dioxide, or silica (SiO2), which quartz glass consists of. In order to obtain the nanospheres, the authors used a spherical prototype made of organic glass so as to shape the future hydrogen vessel.
At the first stage of the study, the scientists created a shell of silicon dioxide by conducting a chemical reaction between water and a silicon-containing organic compound on the surface of the prototype. By firing the prototype and the shell surrounding it at a temperature of several hundred degrees, they obtained a container made of quartz glass that was impermeable to many substances except hydrogen. The resulting hollow nanospheres were 289 nanometers in diameter, while the shell was 25 nanometers thick.
In a later experiment, the scientists saturated the nanospheres with hydrogen at a temperature of 140 degrees Celsius and a pressure of 75,000 bars (75,000 times higher than atmospheric pressure). As a result, the ratio of hydrogen to silicon dioxide was 0.94, which is the highest hydrogen content in quartz glass to date. Less than a third of the hydrogen fit in the cavities of the spheres, and the rest went in their shells.
Analysis showed that under normal external pressure and a temperature of minus 193 degrees Celsius (at a higher temperature, hydrogen quickly leaves the nanospheres), hydrogen molecules form gas in nanosphere cavities and a solid solution in their shells. As a result, the density of the gas in nanosphere cavities is 52 times higher than it is at normal pressure. Crucially, the shape of the nanospheres remained unchanged after they were filled with hydrogen at high pressure.
As part of the study, the scientists decided to determine how long the synthesized particles can retain hydrogen stored in liquid nitrogen, i.e., at a very low temperature (minus 196 degrees Celsius). They found that hydrogen content in the nanospheres dropped by 14% in the first three days under these conditions, only to stop changing later. This means that the resulting nanospheres can be used for long-term storage and transportation of gaseous hydrogen.
“Silicon dioxide is an eco-friendly and affordable material. Moreover, hydrogen isotopes, such as deuterium and tritium, are considered primary fuel components for controlled thermonuclear fusion, which can give humanity an inexhaustible source of energy. The spheres we have synthesized could be used as a vessel for both deuterium and tritium, and could become promising fuel targets in controlled inertial thermonuclear fusion, an area in which technologies are actively developing worldwide,” Vadim Efimchenko, project leader and candidate of physical and mathematical sciences, is quoted as saying by the Russian Science Foundation.
