Carbide-Os Interactions Enhance Deuterium Evolution and Electrolytic Hydrogen Isotope Separation Efficiency

Deuterium gas is primarily produced by electrolysis of high-purity heavy water. Pt/C, the benchmark catalyst for the hydrogen evolution reaction (HER), suffers from high cost, insufficient activity for the deuterium evolution reaction (DER), and poor hydrogen/deuterium separation performance. This study employs the more cost-effective osmium (Os) as the active metal. Leveraging strong metal-support interactions (SMSI) between Os and B₄C or TiC supports, distinct regulatory effects are achieved: B₄C optimizes DER performance, while TiC enhances H/D separation efficiency. Os/B₄C shows ultralow overpotentials of 94 mV in 1 M NaOD and 9 mV in 1 M NaOH at 10 mA·cm^-2, outperforming Pt/C in both activity and stability. Os/TiC exhibits a high isotope separation factor of α_H/D = 6.0 in contrast to 3.5 for Pt/C. X-ray photoelectron spectroscopy reveals that B₄C reduces the electron density of Os, whereas TiC has an opposite effect. H/D underpotential deposition behavior demonstrates weakened adsorption of the deuterium intermediate (D*) on the electron-deficient Os for optimized reaction kinetics and strengthened D* adsorption on the electron-rich Os that slows down DER. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy results show that B₄C facilitates the dissociation of both H₂O and D₂O, while TiC selectively promotes H₂O dissociation, which is found by density functional theory calculations to be a result of the lowered activation barrier of the Volmer reaction in HER. This work provides mechanistic insights into SMSI-mediated tuning of DER kinetics, offering a practical strategy for the design of high-performance DER and D₂O enrichment catalysts.