Direct Hydrogen Quantification in High-pressure Metal Hydrides

Abstract: High-pressure metal-hydride (MH) research evolved into a thriving field within condensed matter physics following the realisation of metallic compounds showing phonon mediated near room-temperature superconductivity. However, severe limitations in determining the chemical formula of the reaction products, especially with regards to their hydrogen content, impedes a deep understanding of the synthesized phases and can lead to significantly erroneous conclusions. Here, we present a way to directly access the hydrogen content of MH solids synthesised at high pressures in (laser-heated) diamond anvil cells using nuclear magnetic resonance (NMR) spectroscopy. We show that this method can be used to investigate MH compounds with a wide range of hydrogen content, from MHx with x=0.15 (CuH0.15) to x < 6.4 (H 6+-0.4 S 5).