NIMSAWARD2025-abstracts

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P2-372Fig. 6: A device that donates electrons to gaseous hydrogen to form hydride. Pd absorbs hydrogen, while Mo blocks it.Key Words: hydride ion, ion conduction Hydrogen drives industrial reduction; the hydride anion (H⁻) is an even stronger reductant that can convert stable CO₂ into fuels/chemicals. Our work targets: selective generation of H⁻, its storage and transport within solids, stable low-loss metal|electrolyteinterfaces, and durable operation for CO₂ hydrogenation under mild voltages advancing carbon neutrality and circularity.Hydrides can hydrogenate carbon dioxide and convert it into value-added compounds.Oxides stabilize hydride ions (H⁻) and enable their fast conduction.ConclusionPreparation of LaH3−2xOxHydride ion uptake and conductionWe aim to: (i) Produce hydrides from water electrolysis, (ii) Use them to electrolytically hydrogenate CO₂to produce formic acid and methanol.Future PlanIntroductionResults & Approach: We discovered room-temperature hydride conductors, rare-earth oxyhydridesREH₃₋₂ₓOₓ, with conductivities comparable to dry proton conductors and >10³×prior H⁻ media. A capacitor-like Pd|REH₃₋₂ₓOₓdevice electrically toggles H₂ ⇄H⁻ and will couple to water-splitting and CO₂ reduction. Benefits: ambient, fossil-free routes to alcohols. Theme underDiscussionHydrogen Ion Materials Group, GREEN Soshi IimuraE-mail：： Iimura.soshi@nims.go.jpHydrogen Ion Uptake and Diffusion in Solids and Their Catalytic Applications(3−2x)LaH3+ x La2O3→ 3LaH3−2xOx0 ≦x≦1, 400℃, Hydrogen atmospherex= 0.25,0.2, 0.15, 0.1, 0.05, 0e−H−1/2H2PdMoREHOVFig. 4: DC polarization measurementusing Mo as a hydrogen-blocking electrode.Fig. 5: Ionic conductivitymeasured under an applied AC (impedance) signal.(x= 1)Hydride ions that moveas fast as protons behavealmost like a liquid.Fig. 8: Arrhenius plot of proton (solid lines) and hydride ion conductivities (symbols).Fig. 9: MD results using machine-learning potentials (stroboscopic snapshots of hydride ions).Fig. 7: When hydride is incorporated, electrons in the oxide are depleted and the electrical resistance decreases. (½ H₂ + e⁻ → H⁻)K. Fukui, SI*et al., JACS(2022).T. Yamasaki, R. Takaoka, SI*et al., ACS Appl. Mater. Interfaces,(2022).Hydride extractionHydride intercalationCurrentVoltageFig.2: Crystal structure of LaH3−2xOxFig.1: Neutron powder diffraction pattern at x= 0.2.LaHOFig. 3: An electric furnace directly connected to a glovebox.