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 αH/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.