New porous water ice metastable at atmospheric pressure obtained by emptying a hydrogen filled ice

TL;DR

This paper reports the discovery and characterization of a new metastable form of water ice, ice XVII, created by removing hydrogen from a hydrogen-filled ice, with potential for reversible hydrogen adsorption.

Contribution

It introduces a novel metastable ice phase, ice XVII, characterized by neutron diffraction and Raman spectroscopy, and demonstrates its reversible hydrogen adsorption capabilities.

Findings

First characterization of ice XVII structure.

Demonstrated reversible hydrogen adsorption and release.

Identified temperature-dependent hysteresis in hydrogen cycling.

Abstract

The properties of some forms of water ice reserve still intriguing surprises. Besides the several stable or metastable phases of pure ice, solid mixtures of water with gases are precursors of other ices, since in some cases they may be emptied, leaving a metastable hydrogen bound water structure. We present here the first characterization of a new form of ice, obtained from the crystalline solid compound of water and molecular hydrogen called C$_0$ filled ice. By means of Raman spectroscopy, we measure the hydrogen release at different temperatures, and succeed in rapidly removing all the hydrogen molecules, obtaining a new form of ice (ice XVII). Its structure is determined by means of neutron diffraction measurements. Of paramount interest is that the emptied crystal can adsorb again hydrogen and release it repeatedly, showing a temperature dependent hysteresis.