Search

[Display omitted] • Nitrogen-doping enhances the H+ and D+ permeability of graphene. • D+ permeates across pyridinic-N defects faster than H+, showing an inverse KIE (0.75). • A normal KIE (1.56) is observed in pyrrolic-N defects. • KIE is influenced by the chemisorption and effective size imparted by defects. Graphene is becoming an increasingly popular platform for developing high-efficiency hydrogen isotope separation technologies operated at room temperature. However, its performance can be strongly affected by contributions from atomic defects. Understanding the influence of defects on the hydrogen isotope selectivity of graphene is thus imperative but remains elusive. In this work, we investigated the electrically driven proton/deuteron permeation through nitrogen-doped graphene membranes with varying N concentrations and configurations. The results show that N-doping significantly enhances the proton and deuteron permeability of graphene (by one order of magnitude). More importantly, deuterons are found to permeate faster through pyridinic N-containing defects than protons, demonstrating a pronounced inverse kinetic isotope effect (KIE) with k H / k D of 0.75. Conversely, pyrrolic N-containing defects exhibit a normal KIE (k H / k D = 1.56). The exclusive contribution of the pyridinic N to the inverse KIE is confirmed by the reversed KIE factor of the pyridinic N-dominated sample subjected to modification. Theoretical calculations indicate that the explicit dependence of KIE on N configuration originates from the different leading mechanisms of proton/deuteron permeation through these N-containing defects, which is governed by the size and the chemisorption imparted by defects. These findings provide fundamental insights into the correlation between defect characteristics and proton/deuteron transport in graphene, and contribute to developing economical hydrogen isotope separation technologies through the defect engineering of graphene. [ABSTRACT FROM AUTHOR]

Zeolites have been considered to be viable candidates for hydrogen isotopes separation in a technological scale due to the well-defined channel, low cost and good thermal and radiation stability. Here, we report a strategy to separate hydrogen isotopes using Ag(I) exchanged ZSM-5(Ag(I)-ZSM-5) zeolite based on strong chemical affinity quantum sieving (CAQS) effect. The thermal desorption spectra (TDS) results reveal that the hydrogen isotope separation on Ag(I)-ZSM-5 zeolite can be achieved at and above liquid nitrogen temperature with a D 2 /H 2 selectivity of 8.7 at 77 K. In addition, 95.1% of deuterium can be enriched through three adsorption/desorption cycles from a mixture with a deuterium concentration of 2.5%. Structural characterization and density functional theory calculations reveal that the high hydrogen isotope selectivity of Ag(I)-ZSM-5 zeolite can be attributed to the strong chemical affinity on Ag(I) site with a large hydrogen isotope effect. Moreover, the hydrogen isotope selectivities (including S (D 2 /DH), S (T 2 /D 2), S (T 2 /TD) and S (T 2 /TH)) on Ag(I)-ZSM-5 are predicted under difference temperatures. Control of the chemical affinity quantum sieving effect of active sites in pore interiors of easily scalable zeolites has unlocked their potential in challenging hydrogen isotopes separation. Image 1 • Strong interaction of the hydrogen molecules with Ag(I) sites is observed. • S (D 2 /H 2) is 8.7 for the Ag(I)-ZSM-5 zeolite at 77 K. • 2.5% D 2 can be enriched to 95.1% D 2 by temperature swing cycles. • S (T 2 /D 2) and S (T 2 /H 2) are predicted by DFT calculations. [ABSTRACT FROM AUTHOR]

Electrolysis of water offers an efficient and eco-friendly route to separate hydrogen isotopes and cathode electrocatalysts featuring high separation factors coupled with high activity and stability are increasingly in demand. In this work, we propose MoS 2 rich in edge sites (MoS 2 -RS) as a promising hydrogen isotope separation electrocatalyst for the first time. MoS 2 -RS cathode exhibits high activity and hydrogen isotope selectivity with a low overpotential of 182.4 mV at 10 mA cm−2, a small Tafel slope of 61 mV dec−1 and a high hydrogen-deuterium separation factor (S H/D) of 10.22 in contrast to 6.33 for the commercial Pt/C catalyst. Density functional theory calculations ascribe the high selectivity of MoS 2 -RS to the H/D zero-point energy difference. Moreover, MoS 2 -RS demonstrates much higher values of S H/D compared with Pt/C catalyst under all test conditions and good long-term stability under acidic conditions. This work not only provides a promising catalytic material for efficient electrolytic separation of hydrogen isotopes but also indicates the direction of rational design of it. [Display omitted] [ABSTRACT FROM AUTHOR]