Hydrogen Isotope Effects Research Articles

Luminescence Modulation in Boron-Cluster-Based Luminogens via Boron Isotope Effects.

Recent advances in luminescent materials highlight the significant impact of hydrogen isotope effects on improving optoelectronic properties. However, the research on the influence of the boron isotope effects on photophysical properties remains underdeveloped. This study focused on exploring the boron isotope effects in boron-cluster-based luminogens. In doing so, we designed and synthesized carborane-based luminogens containing 98% 10B and 95% 11B, respectively, and observed distinct photophysical behaviors. Compared to the 10B-enriched luminogens, the 11B-enriched counterparts can significantly enhance luminescence efficiency, prolong emission lifetime, and reduce full-width at half-maximum. Additionally, increased thermal stability, redshifted B-H vibrations, and a fourfold enhanced electrochemiluminescence intensity have also been observed. On the other hand, the biological assessments of a 10B-enriched luminogen reveals low cytotoxicity, high boron uptake, and excellent fluorescence imaging capability, indicating the potential application in boron neutron capture therapy (BNCT). This work presents the first comprehensive exploration on the boron isotope effects in boron clusters, and provides valuable insights into the rational design of organic luminogens for advanced optoelectronic and biomedical applications.

Luminescence Modulation in Boron‐Cluster‐Based Luminogens via Boron Isotope Effects

Recent advances in luminescent materials highlight the significant impact of hydrogen isotope effects on improving optoelectronic properties. However, the research on the influence of the boron isotope effects on photophysical properties remains underdeveloped. This study focused on exploring the boron isotope effects in boron‐cluster‐based luminogens. In doing so, we designed and synthesized carborane‐based luminogens containing 98% 10B and 95% 11B, respectively, and observed distinct photophysical behaviors. Compared to the 10B‐enriched luminogens, the 11B‐enriched counterparts can significantly enhance luminescence efficiency, prolong emission lifetime, and reduce full‐width at half‐maximum. Additionally, increased thermal stability, redshifted B–H vibrations, and a fourfold enhanced electrochemiluminescence intensity have also been observed. On the other hand, the biological assessments of a 10B‐enriched luminogen reveals low cytotoxicity, high boron uptake, and excellent fluorescence imaging capability, indicating the potential application in boron neutron capture therapy (BNCT). This work presents the first comprehensive exploration on the boron isotope effects in boron clusters, and provides valuable insights into the rational design of organic luminogens for advanced optoelectronic and biomedical applications.

The Regulation Mechanism and Evaluation Model of the Hydrogen Isotope Effect for Zr-Ti-Co Alloys during the Hydrogen/Deuterium Desorption Process at High Temperatures

The Regulation Mechanism and Evaluation Model of the Hydrogen Isotope Effect for Zr-Ti-Co Alloys during the Hydrogen/Deuterium Desorption Process at High Temperatures

Hydrogen isotope effect on thermodynamic and kinetic properties of Pd based ternary alloys: Pd–Ag-M (M = Au, Zr)

Owing to the importance of hydrogen and its isotopes in energy sector, the present study investigates thermodynamic and kinetic hydrogen isotope effects on desorption reaction of newly synthesized Pd-based ternary alloy-hydrides/deuterides viz., Pd0.89Ag0.05M0.06 (M = Au, Zr)–H/D. Alloys were prepared by arc melting method followed by characterization using PXRD, SEM, TXRF and EDX techniques. The effect of hydrogen isotopes on thermodynamics of H2/D2 desorption reaction was investigated by generating pressure-temperature isotherms (PCIs) at various temperatures using a Sieverts' type volumetric apparatus. The PCT diagram of alloys depicts a single plateau which confirms desorption to be a one-step process. Both alloy systems display a normal isotope effect as indicated by higher plateau pressure for deuterides as compared to hydrides. The enthalpy and entropy changes for the desorption reactions were calculated using Van't Hoff equation. The separation factor derived from PCT data indicates that Pd0.89Ag0.05Au0.06 alloy has a significantly high separation factor as compared to other Pd based alloys reported in the literature. To get more insight into this behavior, non-isothermal kinetic analysis of H2/D2 desorption based on Differential Scanning Calorimeter (DSC) data acquired at four different heating rates was conducted and activation energies of desorption were calculated by invoking Kissinger's equation. The activation energies of alloys were found to be lower than that of palladium which explains the high separation factor of alloys as compared to Pd. The desired combination of higher separation factor and lower activation energy makes Pd0.89Ag0.05Au0.06 alloy a promising material for practical application in the separation of hydrogen isotopes via self-displacement gas chromatography (SDGC).

Transport study on development of fuels and ash density profiles in start-up phase of JA DEMO using TASK code

This study has investigated the effect of particle transport of fuel ions (deuterium (D) and tritium (T)) and helium ash (He) as well as their heat transport on the nuclear fusion output in a DEMO reactor. The result was assessed and possible start-up scenarios for DEMO was discussed. In the study, the integrated tokamak modeling code, TASK/TR is used, and for turbulent transport model, the current diffusive ballooning mode (CDBM) has been utilized to investigate the hydrogen isotope effect on the fusion power output. Also, the effect of He build up has been discussed by introducing the mass-dependent enhancement of He transport. The result has suggested that efficient fueling of D and T to the core region of burning plasma with internal transport barrier is difficult without anomalous inward pinch, and helium build up is significant when only neoclassical and CDBM type of turbulent transport is considered for particle transport.

Applicability of self-consistent reaction field (SCRF) method to DFT estimation of hydrogen isotope separation factors in reversible processes

ABSTRACT In earlier quantum chemical calculations of isotope effects, chemical species in the liquid phase were generally treated as existing in the gas phase. In recent years, however, advances in computational programs have made it easier for the self-consistent reaction field (SCRF) method to handle chemical species in the liquid phase, and as a result, it has become easier to apply the SCRF method to isotope effect calculations. This paper concerns the scope of application of the DFT-SCRF method to reversible processes for hydrogen isotope enrichment. It is found that the applicability of the method depends on the type of the intermolecular interaction in the liquid phase and the degree of hydrogen isotope effect (separation factor) on which the process is based. When the magnitude of the isotope effect of the separation system is greater than 10–1, the simple SCRF method is fully applicable; when the magnitude is around 10–2, SCRF with a dimer model, in which the monomer is replaced by a dimer, is applicable for the analysis of the liquid phase with relatively strong intermolecular interactions. Anharmonic correction to the separation factor calculated based on harmonic frequencies may be effective to systems with the liquid phase with weak intermolecular interactions.

Isotope engineering achieved by local coordination design in Ti-Pd co-doped ZrCo-based alloys

Deuterium/Tritium (D/T) handling in defined proportions are pivotal to maintain steady-state operation for fusion reactors. However, the hydrogen isotope effect in metal-hydrogen systems always disturbs precise D/T ratio control. Here, we reveal the dominance of kinetic isotope effect during desorption. To reconcile the thermodynamic stability and isotope effect, we demonstrate a quantitative indicator of Tgap and further a local coordination design strategy that comprises thermodynamic destabilization with vibration enhancement of interstitial isotopes for isotope engineering. Based on theoretical screening analysis, an optimized Ti-Pd co-doped Zr0.8Ti0.2Co0.8Pd0.2 alloy is designed and prepared. Compared to ZrCo alloy, the optimal alloy enables consistent isotope delivery together with a three-fold lower Tgap, a five-fold lower energy barrier difference, a one-third lower isotopic composition deviation during desorption and an over two-fold higher cycling capacity. This work provides insights into the interaction between alloy and hydrogen isotopes, thus opening up feasible approaches to support high-performance fusion reactors.

Hydrogen and deuterium adsorptions and their equilibrium isotope effect on tungsten in alkaline solutions

The equilibrium isotope effect (EIE) of hydrogen isotopes (H and D) on the W electrode in alkaline aqueous (H2O) and heavy water (D2O) solutions was empirically studied based on the relevant electrochemical adsorption isotherms, which were determined using the phase-shift method and electrochemical impedance spectra. For a fractional surface coverage range of 0.2 < θ < 0.8, the potential differences (ΔE) for hydrogen isotope adsorptions on the W electrode were 70 mV, which were much lower than those on the Ni, Ti, Pd, and Rh electrodes. Furthermore, the value of EIE on the W electrode was 13.4, significantly higher than that on the Ti and most Pt-group metal (Pt, Ir, Pt–Ir alloy, and Rh) electrodes. The W electrode can therefore be considered as a potential electrocatalyst for optimizing the hydrogen and deuterium evolution reactions (HER and DER) and EIE of hydrogen isotopes, particularly in water electrolysis and the hydrogen isotope effect.

Thermal-assisted resistive sensor based on the PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere

The detection of hydrogen isotopes is not only the premise of ensuring safety of hydrogen energy, but also has very important application value and scientific significance in the field of fusion energy. Therefore, it is imperative to develop efficient and reliable hydrogen isotope sensors. Herein, a thermal-assisted resistive sensor is constructed based on the hydrogen isotope effect of PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere. The permeation of hydrogen isotopes in palladium lattice is facilitated through thermal effect to improve the dynamic response capability of sensor. The research results show that the response time of sensor to hydrogen and deuterium is reduced from 192 s to 113 s–17 s and 10 s respectively. However, the sensitivity deteriorated by about 40% at 110 °C compared with room temperature. Meanwhile, the PdCr alloy thin film resistive sensor represents a remarkable linear response in a range of 0.1%–4% hydrogen and deuterium, with correlation coefficients of 0.9971 and 0.9998 respectively. And the response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. Furthermore, the sensor exhibits prominent selectivity, extraordinary working stability and a wide range of 100ppm-100%. Therefore, this work presents a feasible approach to design high-performance resistive hydrogen isotope sensors for the development of hydrogen energy and fusion energy.

Studying the isotopic composition of microbial methane with a genetically-tractable methanogen

Nearly all biogenic methane is produced by a group of microorganisms called methanogenic archaea (or methanogens). Methanogens can use a variety of substrates, such as H2 + CO2, acetate, and methylated compounds, for methanogenesis. Previous studies have shown that the stable carbon and hydrogen isotopic compositions of methane produced by methanogens can vary drastically depending on the substrate composition and concentration in the environment. For instance, the concentration of H2 in the environment has a substantial impact on the isotopic composition of methane derived from hydrogenotrophic methanogenesis (reduction of CO2 to methane using H2 as the electron donor) (Valentine et al. 2004, Penning et al. 2005). While there is substantial empirical data on isotopic signatures of methane from different substrates and under different conditions, the physiological and molecular features that control these values are not as well understood. To address this, we are using the metabolically diverse and genetically tractable methanogen, Methanosarcina acetivorans as a model system to uncover key cellular processes that control the stable bulk isotopic composition of methane (i.e., 13C/12C and D/H ratios), and the distributions of the “clumped” 13CH3D and 12CH2D2 isotopologues. The methanogen M. acetivorans grows on a wide variety of compounds such as acetate, methanol, methylamines, and methylsulfides. We found that the methylotrophic pathways (for methanol and trimethylamine) and the aceticlastic pathway have large and similar primary hydrogen isotopic effects (α of ~0.45). These data are in contrast to previous findings and imply a minor isotopic exchange between CH4 and H2O (Valentine et al. 2004, Gruen et al. 2018). Focusing first on the methylotrophic pathway, we generated mutants of two key enzymes in the methylotrophic pathway: a) methyl coenzyme M reductase (Mcr) that catalyzes the last step in methanogenesis and b) methyltransferases that catalyze the first step in methylotrophic methanogenesis from methanol (Mta). A mutant with reduced Mcr expression had no observable change in the hydrogen isotopic effect relative to the wild-type, validating the initial observation of minimal H2O-CH4 hydrogen isotopic exchange. One of the Mta mutants, which only expressed a specific methyltransferase isoform, had a smaller carbon isotopic effect relative to the other isoforms (α of ~1.074 vs. ~1.080). Since the isoforms are thought to be identical in structure, the different isotopic effects could result from differential expression of each isoform, or from different kinetic properties. By combining our genetic approaches with traditional and high-resolution isotopic analytical methods, we aim to develop a quantitative understanding of the mechanisms that control the isotopic compositions of biological methane. Our preliminary results show that M. acetivorans would be an ideal candidate for such research, which could help in understanding methanogens’ physiology in natural environments in past, present, and future Earth.

Carbon and hydrogen stable isotope fractionation due to monooxygenation of short-chain alkanes by butane monooxygenase of Thauera butanivorans Bu-B1211.

Multi element compound-specific stable isotope analysis (ME-CSIA) is a tool to assess (bio)chemical reactions of molecules in the environment based on their isotopic fingerprints. To that effect, ME-CSIA concepts are initially developed with laboratory model experiments to determine the isotope fractionation factors specific for distinct (bio)chemical reactions. Here, we determined for the first time the carbon and hydrogen isotope fractionation factors for the monooxygenation of the short-chain alkanes ethane, propane, and butane. As model organism we used Thauera butanivorans strain Bu-B1211 which employs a non-haem iron monooxygenase (butane monooxygenase) to activate alkanes. Monooxygenation of alkanes was associated with strong carbon and hydrogen isotope effects: εbulkC = -2.95 ± 0.5 ‰ for ethane, -2.68 ± 0.1 ‰ for propane, -1.19 ± 0.18 ‰ for butane; εbulkH = -56.3 ± 15 ‰ for ethane, -40.5 ± 2.3 ‰ for propane, -14.6 ± 3.6 ‰ for butane. This resulted in lambda (Λ ≈ εHbulk/εCbulk) values of 16.2 ± 3.7 for ethane, 13.2 ± 0.7 for propane, and 11.4 ± 2.8 for butane. The results show that ME-CSIA can be used to track the occurrence and impact of monooxygenase-dependent aerobic processes converting short-chain alkanes in natural settings like marine and terrestrial seeps, gas reservoirs, and other geological formations impacted by natural gas.

Thermodynamics and kinetics hydrogen isotope effects of hydrogen/deuterium absorption in Pd-5wt.%Pt alloy

Palladium–Platinum (Pd–Pt) alloys have excellent hydrogen isotope separation properties near room temperature compared to pure palladium (Pd), and are expected to be used as filling materials in thermal cyclic absorption (TCAP) columns. However, most studies on the thermodynamic and kinetic hydrogen isotope effects of hydrogen absorption/deuterium in Pd–Pt alloys have been conducted at temperatures of 273 K or above, with few studies involving the performance of TCAP in the cold-cycle operating temperature range (253 K–303 K). In this work, the performance of Pd-5wt.%Pt alloy for the absorption of hydrogen/deuterium at low temperatures (263 K–323 K) was investigated. The results show that the enthalpy and entropy of dissolution of hydrogen and deuterium in the α-phase of Pd-5wt.%Pt alloy are −11.77 kJ/mol (H), 104.00 J mol−1 K−1(H); −5.50 kJ/mol (D), 87.88 J mol−1 K−1 (D), respectively, which are lower than the enthalpy and entropy change values of pure Pd materials. The apparent reaction activation energies of protium and deuterium absorption are −4.14 kJ/mol (H2) and −11.87 kJ/mol (D2), respectively, which are lower than those of pure palladium. The excellent hydrogen isotope separation performance of Pd–Pt alloys may originate from the fast hydrogen absorption and discharge isotope kinetic performance.

Isotopic evidence (δ13C, δ37Cl, δ2H) for distinct transformation mechanisms of chloroform: Catalyzed H2-water system vs. zero-valent iron (ZVI)

Catalytic hydrodechlorination is an efficient technology for degrading organochlorinated compounds, such as chloroform (CF), into harmless products. Compound-specific stable isotope analysis (CSIA) of multiple elements is widely used for the investigation of degradation mechanisms. Yet, its application in the study of catalytic hydrodechlorination is still limited. We have applied CSIA to derive chlorine, carbon, and hydrogen isotope enrichment factors (ε) during the degradation of CF over Pd/Al2O3 and over Rh/Al2O3. In addition, the enrichment factors for the same isotopes were derived for the reaction of CF with zero-valent iron (ZVI) for comparison. For the reactions of CF over Pd/Al2O3 and Rh/Al2O3, εC values (−21.9 ± 0.25 ‰ and −23.4 ± 2.3 ‰) and εCl values (−12.1 ± 1.7 ‰ and −10.3 ± 0.6 ‰) were determined, respectively. The corresponding εC and εCl values, for the dechlorination of CF with ZVI were −22.2 ± 2.8 ‰ and −4.7 ± 0.45 ‰, respectively. The apparent kinetic isotope effects (AKIE) of Cl suggest that the transformation mechanism in the catalyzed hydrogen-water system is a non-concerted reaction, unlike the known reductive dechlorination of CF with ZVI. Moreover, dual-isotope slopes (ΛC/Cl) for both catalyzed reactions (ΛPd = 1.8 ± 0.13 and ΛRh = 2.1 ± 0.14) are markedly different than for the ZVI (ΛZVI = 5.8 ± 0.41), reflecting that the reactions proceed in different mechanisms. For hydrogen isotopes, while there was no clear trend for the catalyzed reactions, an inverse secondary hydrogen isotope effect was observed for the reaction of CF with ZVI.

Kinetic hydrogen isotope effects and flow compensation strategy of the ZrCo-based chemical beds in full-scale SDS demo-system

ZrCo-based bed, commonly exploited to efficiently process large quantities of mixed hydrogen isotope gases, is one of crucial component in the storage and delivery system (SDS) of the tritium plant in fusion reactor. However, the hydrogen isotope effect on the desorption and adsorption processes of the ZrCo based assemblies has not yet clearly addressed, especially for a full-scale (100 g of Tritium) bed assembly. Herein, the kinetic hydrogen isotope effect of the full-scale ZrCo-based chemical beds, including ZrCo, Zr0.8Ti0.2Co, Zr0.8Hf0.2Co, with different hydrogen isotope ratios in SDS demo-system are investigated in detail. This work shows that the kinetic adsorption isotope effect of all ZrCo based beds are independent of pressure, temperature, and hydrogen isotope ratio. Conversely, the kinetic hydrogen isotope fluctuation is prominent during hydrogen desorption, where the proportion of protium is relatively high at the initial stage. After that, deuterium is easier to release. Finally, the protium gradually increases. The fluctuating degree is in the sequence of Zr0.8Ti0.2Co > ZrCo > Zr0.8Hf0.2Co for types of chemical beds, and 50%D + 50%H > 90%D + 10%H > 10%D + 90%H for isotope components. Based on experimental details, a flow compensation approach to ensure a stable ratio of hydrogen isotope gas is proposed. This work is of crucial significance for practical-scale SDS system operation, which is the prerequisite for the steady-state running of the fusion reactor.

First‐Principles Estimation of Low‐Pressure Superconductivity in KC2H8 Ternary Hydride

Very recently, much research progress has been made on the pressure‐induced superconducting state in ternary hydrides. Herein, an ab initio study of the KC2H8 ternary system is presented at a pressure in the range of 0–100 GPa. Its structural, electronic, dynamical, and superconducting properties are investigated, demonstrating that, at low pressure, KC2H8 is dynamically stable in a clathrate structure with space group Fmm and exhibits superconducting behavior with critical temperatures Tc in the range of 4–94 K. The important role played by C‐ and K‐derived phonon modes at low frequencies and H‐derived phonon modes at high frequencies is highlighted. Moreover, through the analysis of the hydrogen isotope effect, the conventional phonon‐mediated pairing mechanism in this system is proved.

A fresh look at thermal cycling absorption process for hydrogen isotopes separation by dynamic simulation: Initial feeding process and total reflux mode

Thermal Cycling Absorption Process (TCAP) is an important method to separate hydrogen isotopes for the production and engineering application of tritium. There are so many influencing factors that it is difficult to fully understand the influence mechanisms only through experiments. A new simulation model of TCAP was developed. Using the simulation model, the influencing trend and optimized value of parameters of initial feeding process and total reflux mode in TCAP are obtained as follows. (1) The temperatures of initial feeding and the cold cycle are not the lower the better as commonly assumed but exists an optimal value of 30 °C in initial feeding and -20 °C in the cold cycle. (2) The heating rate and cooling rate also exist optimal values of 45 °C/min and 55 °C/min (3) Lower feeding rate is conducive to a better separation effect of hydrogen isotopes. (4) Increasing the reflux ratio benefits the enrichment of heavy hydrogen isotope at the product side but not the light hydrogen isotope at the tail side. (5) It needs more cycles to achieve the same isotope abundance in D/T separation than H/D separation and the separation degree of hydrogen isotopes exists a maximum value after multiple cycles. The findings can provide references for the process optimization and the device design of TCAP, and also can shed new light on the understanding of the basic physical and chemical process of TCAP.

Hydrogen isotope effects: A new path to high-energy aqueous rechargeable Li/Na-ion batteries

Aqueous rechargeable Li/Na-ion batteries have shown promise for sustainable large-scale energy storage due to their safety, low cost, and environmental benignity. However, practical applications of aqueous batteries are plagued by water's intrinsically narrow electrochemical stability window, which results in low energy density. In this perspective article, we review several strategies to broaden the electrochemical window of aqueous electrolytes and realize high-energy aqueous batteries. Specifically, we highlight our recent findings on stabilizing aqueous Li storage electrochemistry using a deuterium dioxide-based aqueous electrolyte, which shows significant hydrogen isotope effects that trigger a wider electrochemical window and inhibit detrimental parasitic processes.

Temperature dependence of hydrogen isotope effect in LaNi5-H(D) system

To study inverse effect of hydrogen isotopes in LaNi5 for hydrogen isotope separation at ambient temperature, temperature dependence of hydrogen isotope effect in LaNi5－H(D) system was investigated in the temperature range -70 °C to 3 °C. Isotherms of hydrogen isotopes were tested in an automated Sieverts apparatus with a thermostat, and pressure differences were studied between H2 and D2. Isotope exchange process was carried out and H2－HD－D2 equilibrium was judged by online chromatography, separation factors were calculated to investigate the thermodynamic isotope effect. In the H2, D2 isotherms, average time interval (0.5h) between each equilibrium point was relatively short due to high precision temperature control. From the plateau pressures at a constant hydrogen (or deuterium) concentration in LaNi5 (2D or 2H atoms/mole of LaNi5) the partial molar enthalpies, ⊿H, and entropies, ⊿S of formation were calculated. ⊿H and ⊿S kept good accordance with the values from references, which indicated good performance of the Sieverts apparatus. The isotope exchange equilibrium was reached within 1h. The results showed that ratio between H2 pressure and D2 pressure, r(H－D) = P(D2)/P(H2), dropped as temperature decreased and the inverse effect was found (r(H－D)<1.0) below -5 °C according to the absorption branch of isotherms, whereas the effect was estimated to appear below 60 °C from the desorption branch. The separation factor of the H2－HD－D2 mixture, decreased as temperature increased and the inverse effect happened below -20 °C. The inverse effect was affected by the isotherm hysteresis and HD existence.

Isotope effect on hydrogen storage properties of Ti and Nb co-substituted ZrCo alloy

In our previous study, we showed that the anti-disproportionation properties of Zr0.8Ti0.2-xNbxCo alloys were remarkably improved by the co-substitution of Zr with Ti and Nb. However, the practical application of these alloys in handling of hydrogen isotopes necessitates the first hand knowledge of hydrogen isotope effect. Herein, we discuss the hydrogen isotope effect on storage properties of Zr0.8Ti0.2-xNbxCo alloys. According to PCT measurements on desorption of deuterium from the Zr0.8Ti0.2-xNbxCo deuterides and comparison with corresponding hydrides, the deuterides require relatively lower temperature to achieve the desired equilibrium pressure. DSC measurements reveal a significant decrease in the activation energy for hydrogen/deuterium desorption reactions when Zr is substituted with Ti and Nb. Furthermore, it is observed that the activation energy of deuterium desorption is lower than the desorption of hydrogen from analogous hydride. Isotope effect on isothermal disproportion studies on Zr0.8Ti0.2-xNbxCo-deuterides divulge that Zr0.8Ti0.2-xNbxCo-deuterides have superior anti-disproportionation properties over corresponding hydrides, and further improvement is anticipated for the Zr0.8Ti0.2-xNbxCo-tritides. This study revealed the significant impact of Ti and Nb co-substitution on hydrogen isotope storage properties of Zr0.8Ti0.2-xNbxCo alloys, making them potential candidates for handling hydrogen isotopes.

Hydrogen isotope plasma-driven permeation through RAFM steel: isotope exchange and helium irradiation effect

Hydrogen isotope exchange in China low activation martensitic (CLAM) steel was investigated by plasma-driven permeation (PDP) measurements in the temperature range of ∼670–920 K. It was found that as H was introduced into D plasma, the permeation flux of HD increased while that of D2 decreased. The total D permeation flux, however, remained almost unchanged. Such a result allowed the analysis of isotope replacement and showed that the reduction of D2 is balanced by the rise of HD. In addition, the formation of HD was found to be closely related to the H and D content in plasma. Hydrogen isotopic effects on H and D plasma dissociation/ionization rate and on incident flux were evaluated by measuring plasma parameters including electron temperature and electron density using a triple Langmuir probe. The correlation between isotope effects on ionization rate in the plasma and isotope effects in the permeation flux was discussed. He plasma pre-irradiation and seeding during D PDP were also conducted to investigate the He effects on D diffusion. The total D permeation flux was found to be reduced by He seeding. Data analysis of Langmuir probe showed that ionization rate of D plasma was influenced by He seeding. Besides, under simultaneous D + He irradiation, He atoms were preferentially trapped at the defects resulting in a shallower D concentration gradient that described the observed decrease in D permeation rate. He plasma pre-irradiation was found to reduce D permeation flux with a much slower breakthrough to reach steady-state. The amount of D trapped at He-induced defects was derived quantitatively from the transient permeation curves. It is believed that He bubbles formed at the near surface act as trapping sites of D atoms, leading to a less effective diffusion coefficient and an enhanced retention in the material.