Facile synthesis of palladium hydride via ionic gate-driven protonation using a deep eutectic solvent

Abstract

Developing novel protocols for hydrogen (H) loading is crucial for furthering the investigation of hydrides as potential high-temperature superconductors at lower pressures compared to recent discoveries. Ionic gating-induced protonation (IGP) has emerged as a promising technique for H loading due to its inherent simplicity, but it can be limited in the maximum density of injected H when ionic liquids are used as a gating medium. Additionally, most ionic liquids are limited by high production costs, complex synthesis, and potential toxicity. Here, we demonstrate that large H concentrations can be successfully injected in both palladium (Pd) bulk foils and thin films (up to a stoichiometry PdH${}_{0.89}$) by using a deep eutectic solvent (DES) choline chloride-glycerol 1:3 as gate electrolyte and applying gate voltages in excess of the cathodic stability limit. The attained H concentrations are large enough to induce superconductivity in Pd, albeit with an incomplete resistive transition which suggests a strongly inhomogeneous H incorporation in the Pd matrix. This DES-based IGP protocol can be used as a guideline for maximizing H loading in different materials, although specific details of the applied voltage profile might require adjustments based on the material under investigation.

14 pages, 5 figures

References in corpus (22)

• Conventional superconductivity at 203 K at high pressures
• Superconductivity at 250 K in lanthanum hydride under high pressures
• Controlling many-body states by the electric-field effect in a two-dimensional material
• Towards high-throughput superconductor discovery via machine learning
• Gate tuning of electronic phase transitions in two-dimensional NbSe${}_2$
• Electric-field Control of Magnetism with Emergent Topological Hall Effect in SrRuO3 through Proton Evolution
• Large conductance modulation of gold thin films by huge charge injection via electrochemical gating
• Tunable inverse spin Hall effect in nanometer-thick platinum films by ionic gating
• Emergent electric field control of phase transformation in oxide superlattices
• Control of bulk superconductivity in a BCS superconductor by surface charge doping via electrochemical gating
• Protonation-induced discrete superconducting phases in bulk FeSe single crystals
• Ionic-liquid-gating induced protonation and superconductivity in FeSe, FeSe0.93S0.07, ZrNCl, 1T-TaS2, and Bi2Se3
• Possible charge-density-wave signatures in the anomalous resistivity of Li-intercalated multilayer MoS2
• Huge field-effect surface charge injection and conductance modulation in metallic thin films by electrochemical gating
• Superconductivity induced by gate-driven hydrogen intercalation in the charge-density-wave compound 1T-TiSe2
• Towards the insulator-to-metal transition at the surface of ion-gated nanocrystalline diamond films
• Ionic gating in metallic superconductors: A brief review
• Superconductivity at 44.4 K achieved by intercalating EMIM+ into FeSe
• Orientation-dependent electric transport and band filling in hole co-doped epitaxial diamond films
• Anomalous metallic phase in molybdenum disulphide induced via gate-driven organic ion intercalation
• Reversible Tuning of Superconductivity in Ion-Gated NbN Ultrathin Films by Self-Encapsulation with a High-$\kappa$ Dielectric Layer
• Cluster charge-density-wave glass in hydrogen-intercalated TiSe${}_2$