Improvement in the hydrogen storage properties of Mg by mechanical grinding with Ni, Fe and V under H2 atmosphere

Mg-5wt%Ni-2.5wt%Fe-2.5wt%V (named Mg-5Ni-2.5Fe-2.5V) powder was prepared by reactive mechanical grinding using a planetary ball mill. The activation process, the changes in phase and microstructure with hydriding-dehydriding cycling, and the variations in the hydriding and dehydriding rates with temperature were investigated. The rate-controlling step for the dehydriding reaction of Mg-5Ni-2.5Fe-2.5V was analyzed by using a spherical moving boundary model. As the temperature increased from 473 K through 623 K, the initial hydrogen absorption rate under 12 bar H₂ decreased, while the hydrogen desorption rate under 1.0 bar H₂ increased.     

Improvement of hydrogen-storage properties of MgH2 by Ni,LiBH4, and Ti addition

In this work, differently from our previous work, MgH₂ instead of Mg was used as a starting material. Ni, Ti, and LiBH₄ with a high hydrogen-storage capacity of 18.4 wt% were added. A sample with a composition of MgH₂–10Ni–2LiBH₄–2Ti was prepared by reactive mechanical grinding. MgH₂–10Ni–2LiBH₄–2Ti after reactive mechanical grinding contained MgH₂, Mg, Ni, TiH_1.924, and MgO phases. The activation of MgH₂–10Ni–2LiBH₄–2Ti for hydriding and dehydriding reactions was not required. At the number of cycles, n = 2, MgH₂–10Ni–2LiBH₄–2Ti absorbed 4.09 wt% H for 5 min, 4.25 wt% H for 10 min, and 4.44 wt% H for 60 min at 573 K under 12 bar H₂. At n = 1, MgH₂–10Ni–2LiBH₄–2Ti desorbed 0.13 wt% H for 10 min, 0.54 wt% H for 20 min, 1.07 wt% H for 30 min, and 1.97 wt% H for 60 min at 573 K under 1.0 bar H₂. The PCT (Pressure–Composition–Temperature) curve at 593 K for MgH₂–10Ni–2LiBH₄–2Ti showed that its hydrogen-storage capacity was 5.10 wt%. The inverse dependence of the hydriding rate on temperature is partly due to a decrease in the pressure differential between the applied hydrogen pressure and the equilibrium plateau pressure with the increase in temperature. The rate-controlling step for the dehydriding reaction of the MgH₂–10Ni–2LiBH₄–2Ti at n = 1 was analyzed.     

Improvement of hydrogen storage characteristics of Mg by planetary ball milling under H2 with metallic element(s) and/or Fe2O3

Among samples of Mg-Ni, Mg-Ni-5Fe₂O₃, and Mg-Ni-5Fe, Mg-Ni-5Fe had the highest hydriding and dehydriding rates. For the as-milled Mg-Ni-5Fe alloy and the hydrided Mg-Ni-5Fe alloy after activation, the weight percentages of the constituent phases were calculated using the FullProf program. The creation of defects and the diminution of Mg particle size through reactive mechanical grinding and hydriding-dehydriding cycling, and the formation of the Mg₂Ni phase are considered to increase the hydriding and dehydriding rates. Mg-14Ni-2Fe-2Ti-2Mo had higher hydriding and dehydriding rates than did any of the other samples (Mg-Ni, Mg-Ni-5Fe₂O₃, Mg-Ni-5Fe, and Mg-14Ni-6Fe₂O₃) prepared in this work.     

Hydrogen storage properties of Mg-23.5Ni-xCu prepared by rapid solidification process and crystallization heat treatment

A Mg-23.5wt%Ni-5wt%Cu alloy was synthesized by the gravity casting method in a large quantity (7.5 kg). From this alloy, Mg-23.5wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment. The samples were ground under H₂ in order to obtain a fine powder. These alloys contained crystalline Mg and Mg₂Ni phases. The Mg-23.5Ni-2.5Cu alloy had the highest hydriding and dehydriding rates after activation among these alloys. The dehydriding curve under 1.0 bar H₂ at 573 K exhibits two stages; the dehydriding rate is high for about 2.5 min (the decomposition of Mg₂Ni hydride and Mg hydride in small particles), and then it becomes lower (the decomposition of Mg hydride).     

Enhancement of the hydrogen storage characteristics of Mg by reactive mechanical grinding with Ni,Fe and Ti

Mg-10wt%Ni-5wt%Fe-5wt%Ti powder was prepared by reactive mechanical grinding using a planetary ball mill. The Mg-10wt%Ni-5wt%Fe-5wt%Ti powder exhibited high hydriding and dehydriding rates even at the first cycle, and its activation was completed after two hydriding–dehydriding cycles. After the reactive mechanical grinding, the particle size of the powder was reduced, as compared with those of the starting materials. The hydrogen storage properties were measured at temperatures of 473 K, 573 K and 623 K. The activated Mg-10wt%Ni-5wt%Fe-5wt%Ti powder absorbed 5.31 wt% and 5.51 wt% of hydrogen for 5 min and 1 h, respectively, at 573 K under 12 bar H₂. It desorbed 5.18 wt% of hydrogen at 573 K under 1.0 bar H₂ for 1 h. The initial hydrogen absorption rate increased when passing from 473 K to 573 K, but decreased at 623 K. The hydrogen desorption rate increased rapidly with increasing temperature from 473 K to 623 K. The hydrogen storage capacity was about 6.72 wt% at 573 K.     

Preparation and characterization of NbF5-added Mg hydrogen storage alloy

A sample with a composition of 95 wt% Mg-5 wt% NbF₅ (named Mg-5NbF₅) was prepared by reactive mechanical grinding using Mg instead of MgH₂ as a starting material. Its hydriding and dehydriding rates were then measured under nearly constant hydrogen pressures. The activation of Mg-5NbF₅ was not required, and Mg-5NbF₅ had an effective hydrogen storage capacity, which was defined as the quantity of hydrogen absorbed for 60 min, of 5.50 wt%. At the first cycle (n = 1) at 593 K, the sample absorbed 4.37 wt% H for 5 min and 5.50 wt% H for 30 min under 12 bar H₂, and desorbed 1.03 wt% H for 5 min, 4.66 wt% H for 30 min, and 5.43 wt% H for 60 min under 1.0 bar H₂. Reactive mechanical grinding of Mg with NbF₅, which formed MgH₂, MgF₂, NbH₂, and NbF₃ by the reaction of 11 Mg + 7NbF₅ + 3H₂ → MgH₂ + 10MgF₂ + 2NbH₂ + 5NbF₃, is considered to create defects, to produce reactive clean surfaces, and to reduce the particle size of Mg. The XRD pattern of Mg-5NbF₅ dehydrided at n = 3 revealed Mg, small amounts of β-MgH₂ and MgO, and very small amounts of MgF₂ and NbH₂. An increase in the dehydriding rate of Mg-5NbF₅ was attempted by adding Ni to Mg-5NbF₅. Mg-5NbF₅ had higher initial hydriding and dehydriding (after the incubation period) rates and a larger effective hydrogen storage capacity than Mg-10NbF₅, Mg-10MnO, and Mg-10Fe₂O₃, which were reported to have quite high hydriding rate and/or dehydriding rate.     

Hydrogen storage properties of a Mg–Ni–Fe mixture prepared via planetary ball milling in a H2 atmosphere

A sample composition has been designed based on previously reported data. An 80 wt%Mg–13.33 wt%Ni–6.67 wt%Fe (referred to as Mg–13.33Ni–6.67Fe) sample exhibited higher hydriding and dehydriding rates after activation and a larger hydrogen storage capacity compared to those of other mixtures prepared under similar conditions. After activation (at n = 3), the sample absorbed 4.60 wt%H for 5 min and 5.61 wt%H for 60 min at 593 K under 12 bar H₂. The sample desorbed 1.57 wt%H for 5 min and 3.92 wt%H for 30 min at 593 K under 1.0 bar H₂. Rietveld analysis of the XRD pattern using FullProf program showed that the as-milled Mg–13.33Ni–6.67Fe sample contained Mg(OH)₂ and MgH₂ in addition to Mg, Ni, and Fe. The Mg(OH)₂ phase is believed to be formed through the reaction of Mg or MgH₂ with water vapor in the air. The dehydrided Mg–13.33Ni–6.67Fe sample after hydriding-dehydriding cycling contained Mg, Mg₂Ni, MgO, and Fe.     

Hydrogen storage properties of Mg-10 wt% Ni alloy co-catalysed with niobium and multi-walled carbon nanotubes

Mg-10 wt% Ni alloys containing up to 1 wt% Nb were fabricated by a casting technique, followed by ball-milling with 5 wt% multi-walled carbon nanotubes. Further mechanical alloying with 1.5, 3, and 5 at % Nb was applied to a cast Mg-10 wt% Ni-370 ppm Nb alloy to investigate the catalytic role of Nb in hydrogen dissociation. The microstructure and distribution of Nb and Mg₂Ni in the alloys were characterised by SEM. The absorption and desorption kinetics of the samples were measured by Sieverts’ apparatus at various temperatures. The results show that addition of Nb during casting accelerates the hydrogen diffusion compared to the cast binary Mg-10 wt% Ni alloy. Moreover, ball-milling of the alloy with metallic niobium leads to the formation of BCC phase of Mg-Nb solid solution, which significantly improves the hydrogenation properties of the alloy. DSC results show that mechanical alloying of Mg-10 wt%Ni-370 ppm Nb with Nb in excess of 1.5 wt% decreases the desorption temperature by approximately 100 °C compared to the ball-milled cast alloy.     

Tunable microstructure,de-/hydrogenation kinetics and thermodynamics performance of Mg–Ni–La–Ti–H systems

In the light of positive effects of rare earth and transition metals on the hydrogen absorption/desorption properties of magnesium, the Mg20La–5TiH₂, Mg20Ni–5TiH₂ and Mg10Ni10La–5TiH₂ composites have been prepared in this work to ameliorate the de-/hydrogenation kinetics and thermodynamic performance. The results indicate that the as-prepared composites are mainly composed of Mg, Mg₂Ni/LaH₃ and TiH₂ phases after activation, and LaH₃ and TiH₂ are stable during de-/hydrogenation cycles. The morphology observations give evidences that LaH₃ with size about ~20 nm and Mg₂Ni with size about ~1 μm are uniformly distributed in the composites. It is noted that the de-/hydriding kinetics of the as-prepared composites are significantly improved after internal and surface modification, of which the Mg10Ni10La–5TiH₂ composite can desorb as high as 5.66 wt% hydrogen within 3 min at 623 K. Moreover, the thermodynamic properties of the experimental composites have also been investigated and discussed according to the pressure-composition isothermal curves and corresponding calculation by Van't Hoff equation. The improved hydrogen storage properties of the as-prepared composites are mainly attributed to the uniformly distributed LaH₃, Mg₂Ni and TiH₂ phases, which provide a large amount of phase boundaries, diffusion paths and nucleation sites for de-/hydrogenation reactions.     

Hydrogen-storage properties of gravity cast and melt spun Mg–Ni–Nb2O5 alloys

95%(gravity cast Mg–23.5Ni)–-5%Nb₂O₅ alloy was prepared by horizontal ball milling in n-hexane of gravity cast Mg–23.5wt%Ni with Spex milled Nb₂O₅. Melt spun Mg–23.5wt%Ni after heat treatment at 523 K for 1 h was also ground by planetary ball milling with finer Nb₂O₅ prepared by milling with NaCl. The activated 90%(melt spun Mg–23.5Ni)–10%Nb₂O₅ alloy shows higher hydriding and dehydriding rates than the activated 95%(gravity cast Mg–23.5Ni)–5%Nb₂O₅ alloy, thanks to the homogeneous distribution of fine Mg₂Ni phase in melt spun Mg–23.5Ni and the finer Nb₂O₅ addition to melt spun Mg–23.5Ni, which leads to the effective diminution of the Mg particle size. The activated 90%(ms Mg–23.5Ni)–10%Nb₂O₅ alloy absorbs 4.70 wt%H at 573 K under 12 bar H₂ for 10 min, and desorbs 4.75 wt%H at 573 K under 1.0 bar H₂ for 25 min.     

Enhancement of hydrogen-storage performance of MgH2 by Mg2Ni formation and hydride-forming Ti addition

MgH₂, rather than Mg, was used as a starting material in this work. A sample with a composition of MgH₂–10Ni–4Ti was prepared by reactive mechanical grinding. Activation of the sample was completed after the first hydriding cycle. At n = 1, the sample desorbed 2.53 wt% H for 10 min, 3.99 wt% H for 20 min, 4.58 wt% H for 30 min, and 4.68 wt% H for 60 min at 593 K under 1.0 bar H₂. At n = 2, the sample absorbed 3.59 wt% H for 5 min, 4.55 wt% H for 25 min, and 4.60 wt% H for 45 min at 593 K under 12 bar H₂. The inverse dependence of the hydriding rate on the temperature in the initial stage and the normal dependence of the hydriding rate on the temperature in the later stage were discussed. The rate-controlling step for the dehydriding reaction of activated MgH₂–10Ni–4Ti was analyzed as the chemical reaction at the hydride/α-solid solution interface.     

Modeling and analyzing the hydriding kinetics of Mg-LaNi5 composites by Chou model

Chou model was used to analyze the influences of LaNi₅ content, preparation method, temperature and initial hydrogen pressure on the hydriding kinetics of Mg-LaNi₅ composites. Higher LaNi₅ content could improve hydriding kinetics of Mg but not change hydrogen diffusion as the rate-controlling step, which was validated by characteristic reaction time t_c. The rate-controlling step was hydrogen diffusion in the hydriding reaction of Mg-30 wt.% LaNi₅ prepared by microwave sintering (MS) and hydriding combustion synthesis (HCS), and surface penetration was the rate-controlling step of sample prepared by mechanical milling (MM). Rising temperature and initial hydrogen pressure could accelerate the absorption rate. The rate-controlling step of Mg-30 wt.% LaNi₅ remained hydrogen diffusion at temperatures ranging from 302 to 573 K, while that of Mg-50 wt.% LaNi₅ changed from surface penetration to hydrogen diffusion with increasing initial hydrogen pressure ranging from 0.2 to 1.5 MPa. Apparent activation energies of absorption for Mg-30 wt.% LaNi₅ prepared by MS and MM were respectively 25.2 and 28.0 kJ/mol H₂ calculated by Chou model. Kinetic curves fitted and predicted by Chou model using temperature and hydrogen pressure were well exhibited.     

Hydrolysis H2 generation behavior of AM50 alloy waste coactivated by Mg-based master alloys

Mg-25 wt%Ni (Mg25Ni) or Mg-30 wt%Ce (Mg30Ce) master alloys were firstly introduced by high-energy ball milling (HEBM) to surface activate AM50 alloy waste and activated AM50-Mg25Ni, AM50-Mg30Ce and AM50-Mg25Ni–Mg30Ce are obtained. The hydrolysis H₂ generation behavior are comparatively investigated. The results show that AM50-Mg25Ni with 10 wt% Mg25Ni can rapidly generate 500.1 mL/g H₂ within 5 min at 298 K, which is higher than that of AM50 alloy waste (213.9 mL/g H₂). Mg30Ce master alloy is unsuitable for activation of AM50 alloy waste due to the deterioration initial hydrolysis kinetics (only 90.3 mL/g H₂ in 5 min) originated from the severe agglomeration of AM50-Mg30Ce particles. As high as 427.2 mL/g and 776.5 mL/g H₂ can be generated by coactivated AM50-Mg25Ni–Mg30Ce within initial 5 and 30 min, which are higher than those of AM50 alloy waste (213.9 and 715.7 mL/g H₂) at 298 K. The thermodynamic behaviors of AM50 alloy waste is accelerated by Mg25Ni and Mg30Ce. The E_a of coactivated AM50-Mg25Ni–Mg30Ce sample is 37.1 kJ/mol, which is lower than that of AM50 alloy waste (52.0 kJ/mol) The coactivation effect and mechanism of Mg25Ni and Mg30Ce is investigated. This work provides an effective activation strategy for modification of Mg alloy waste to generate H₂.     

The dehydrogenation performance and reaction mechanisms of Li3AlH6 with TiF3 additive

For Li₃AlH₆ prepared by mechanical milling method, the dissociation reaction enthalpy and activation energy are calculated to be 22.1 kJ mol⁻¹ H₂ and 133.7 ± 2.7 kJ mol⁻¹, respectively. The dehydrogenation performance of Li₃AlH₆ is greatly enhanced by TiF₃ additive, especially in the kinetic behaviors. For the Li₃AlH₆ + 10 mol% TiF₃ sample, the starting temperature of dehydrogenation is obviously decreased by 60 °C from that of pure Li₃AlH₆ (190 °C), and 3.0 wt.% H₂ may be released within 1000 s at 120 °C under an initial vacuum. With the amount of TiF₃ increasing, the starting temperature decreases and the kinetics improves due to the decrease in the activation energy. The X-ray diffraction (XRD) together with thermogravimetric analysis (TGA) results show that there are three mechanochemical reactions involved during milling: i) Li₃AlH₆ + TiF₃ → 3 LiF + Al + Ti + 3H₂, ii) Ti + H₂ → TiH₂, iii) 3 Al + Ti → Al₃Ti. The in-situ formed Ti species (TiH₂ and Al₃Ti) co-catalyze the thermal dehydrogenation of Li₃AlH₆.     

Investigations on gaseous hydrogen storage performances and reactivation ability of as-cast TiFe1-xNix (x=0, 0.1, 0.2 and 0.4) alloys

In this paper, Fe is partly substituted by Ni for improving the hydrogen storage properties of the TiFe alloy, such as the activation performance, hydrogen storage capacity, reactivation ability, optimum temperature range, thermodynamics and kinetics. The as-cast TiFe alloy contains the majority phase of TiFe and the minority phases of Ti₂Fe and TiFe₂. Increasing Ni content causes the majority phase of TiFe to increase firstly and then decrease again. The activation temperature reduces from 573 K for the TiFe alloy to 523 and 443 K for the TiFe_0·8Ni_0.2 and TiFe_0·6Ni_0.4 alloys respectively. Substituting Fe with Ni partly can lower the platform pressure for the P-C-T curves and increase the dehydrogenation enthalpy (ΔH_des). The TiFe_0·8Ni_0.2 alloy possesses the highest hydrogenation capacity. Adding Ni also is beneficial to expand the optimum temperature range, corresponding to the hydrogenation capacity higher than 0.800 wt%, which is 313–383, 313–503 and 313–573 K for the TiFe_1-xNi_x (x = 0.1, 0.2 and 0.4) alloys, respectively. All the alloys can be activated again at 573 K after being exposed to air for 5 min.     

Study on hydrogenation behaviors of a Mg-13Y alloy

The Mg-13Y bulk alloy was prepared by conventional casting process and the Mg-13Y powder was processed by ball milling using the casting alloy under the protection of argon. The hydrogenation thermodynamics, hydrogenation process and phase transitions were carefully investigated in the Mg-13Y powder alloy. It is shown that the Mg-13Y casting alloy consists of Mg₂₄Y₅ phase and α-Mg containing yttrium which have different hydrogenation enthalpies, −195 kJ/mol H₂ (by calculation) and −42 kJ/mol H₂ (by Pressure–Composition–Temperature experiment), respectively. The structure evolution and phase transition in the Mg-13Y bulk alloy treated at 673 K and at 4 MPa for 40 h were observed by an optical microscopy (OM), a scanning electron microscopy (SEM), a transmission electron microscopy (TEM) and X-ray diffraction (XRD). The large Mg₂₄Y₅ phase in the bulk Mg-13Y alloy could be destroyed into fine cuboid-shaped YH₂ phases during the hydrogenation process, which is probably responsible for the improvement of mechanical properties of Mg-13Y alloy.     

Studies on de/rehydrogenation characteristics of nanocrystalline MgH2 co-catalyzed with Ti,Fe and Ni

In the present study, we have investigated the combined effect of different transition metals such as Ti, Fe and Ni on the de/rehydrogenation characteristics of nano MgH₂. Mechanical milling of MgH₂ with 5 wt% each of Ti, Fe and Ni for 24 h at 12 atm of H₂ pressure lead to the formation of nano MgH₂-Ti5Fe5Ni5. The decomposition temperature of nano MgH₂-Ti5Fe5Ni5 is lowered by 90 °C as compared to nano MgH₂ alone. It is also found that the nano MgH₂-Ti5Fe5Ni5 absorbs 5.3 wt% within 15 min at 270 °C and 12 atm hydrogen pressures. However, nano MgH₂ reabsorbs only 4.2 wt% under identical condition. An interesting result of the present study is that mechanical milling of MgH₂ separately with Fe and Ni besides refinement in particle size also leads to the formation of alloys Mg₂NiH₄ and Mg₂FeH₆ respectively. On the other hand, when MgH₂ is mechanically milled together with Ti, Fe and Ni, the dominant result is the formation of nano particles of MgH₂. Moreover the activation energy for dehydrogenation of nano MgH₂ co-catalyzed with Ti, Fe and Ni is 45.67 kJ/mol which is 35.71 kJ/mol lower as compared to activation energy of nano MgH₂ (81.34 kJ/mol). These results are one of the most significant in regard to improvement in de/rehydrogenation characteristics of known MgH₂ catalyzed through transition metal elements.     

The synthesis and characterization of Ni-M-Tb/Al2O3 (M: Mg,Ca, Sr and Ba) nanocatalysts prepared by different types of doping using the ultrasonic-assisted method to enhance CO2 methanation

In the present study, Ni-M-Tb/Al₂O₃ (M: Mg, Ca, Sr and Ba) nanostructured catalysts with different ratios of the alkali metals were synthesized by the ultrasonic-assisted one-pot method. The catalytic performance was investigated in terms of CO₂ conversion, CH₄ selectivity, and stability via the H₂-TPR analysis. The structural properties were delineated using XRD, SEM, TEM and BET equation. The results showed that the 2Ni-5Mg-5Tb/Al₂O₃ catalyst with a maximum CO₂ conversion of 75.37% and CH₄ selectivity of 100%, at the operating temperature of 400 °C in the molar ratio of H₂:CO₂:3.5 for 100 h, had the best performance. This could benefit from the particular electronic structure of Tb in combination with Mg and Ni, reducing agglomeration, as demonstrated by the SEM and BET results. Based on the current findings, novel catalysts with high conversion efficiency of CO₂ to CH₄ might be achieved by tuning a decent combination of alkaline and rear earth elements as the promoters of Ni-based catalysts.     

Hybrid H2/Ti dust explosion hazards during the production of metal hydride TiH2 in a closed vessel

The explosibility of hybrid H₂/Ti dust in the production of metal hydride TiH₂ was simulated and studied using a 20-L spherical vessel. The influential factors for the explosion performance of hybrid H₂/Ti dust, including particle size distribution and polydispersity, humidity, temperature, hydrogen content, inert gas and degree of reaction, on hybrid explosion were investigated. Results showed that both the mean particle sizes and particle size polydispersity had significant effects on the dust severity of hybrid H₂/Ti dust. The explosion severity of hybrid H₂/Ti dust was enhanced at a higher temperature in a certain range, and it presented a trend of increasing at the early stage and then decreased both for the increasing humidity and hydrogen pressure. Explosion inhibition effects of typical inert gases for hybrid H₂/Ti dust increased in the following order: argon < helium < nitrogen. The values of (dP/dt)_ex and V_f decreased along with the reaction process, while the value of P_ex kept stable, which showed that the hydrogen state had no obvious impact on P_ex but significantly affected the explosion risk of hybrid H₂/Ti dust, and special attention should be paid to the initial stages of the production process of TiH₂.     

The optimization of Ni–Al2O3 catalyst with the addition of La2O3 for CO2–CH4 reforming to produce syngas

A series of La₂O₃–NiO–Al₂O₃ catalysts promoted by different loading of lanthanum were prepared via the hydrolysis-deposition method to improve the catalytic performance of nickel-based catalyst for CO₂–CH₄ reforming. The catalysts were characterized by N₂ adsorption - desorption, XRD, H₂-TPR, TG-DTG, TEM, Raman and TPH techniques. Results showed that the precursor of active component was mainly in the form of NiAl₂O₄ spinel, which almost disappeared after reduction process from XRD characterization, suggesting well reduction performance. The catalyst with La loading of 0.95 wt% (La–Ni-1) presented a small average Ni grain size of 7.71 nm and exhibited well catalytic performance at 800 °C, with CH₄ conversion of 94.37%, CO₂ conversion of 97.15%, H₂ selectivity of 75.01% and H₂/CO ratio of 0.92. The Ni grain size of La–Ni-1 increased only 5.84% to 8.16 nm after performance test, which was lower than that of others and indicated a well structure stability. Additionally, the strong carbon diffraction peak over La–Ni-0.5 and La–Ni-2 catalysts suggested the presence of crystalline carbon species accumulated on the catalysts, while there was no carbon peak over La–Ni-1 sample. A 150 h stability test for La–Ni-1 demonstrated that the conversion of CH₄ was around 95%, higher than that of La–Ni-0 (without lanthanum addition) and La–Ni-4 (with La content of 3.82 wt%). The carbon deposition rate of La–Ni-1 was only 1.63 mg/(g_cat·h), lower than that of La–Ni-4 (2.20 mg/(g_cat·h)), showing both high activity and well stability. Therefore, the “confinement effect” of La₂O₃ to Ni crystalline grain would inhibit the sintering of active component, prevent the carbon deposition, and improve the catalytic reforming performance.