One-pot synthesis of supported Ni@Al2O3 catalysts with uniform small-sized Ni for hydrogen generation via ammonia decomposition

Nickel based materials are the most potential catalysts for CO_x-free hydrogen production from ammonia decomposition. However, the facile synthesis of supported Ni-based catalysts with small size Ni particles, high porosity and good structural stability is still of great demand. In this work, uniform small-sized Ni particles supported into porous alumina matrix (Ni@Al₂O₃) are synthesized by a simple one-pot method and used for ammonia decomposition. The Ni content is controlled from 5 at.% to 25 at.%. Especailly, the 25Ni@Al₂O₃ catalyst shows the best catalytic performance. With a GHSV of 24,000 cm³g_cat^?1h^?1, 93.9% NH₃ conversion is achieved at 600 °C and nearly full conversion of NH₃ is realized at 650 °C. The hydrogen formation rate of 25NiAl catalyst reaches 3.6 mmol g_cat^?1min^?1 at 400 °C and 7.8 mmol g_cat^?1min^?1 at 450 °C. The enhanced activity observed on 25Ni@Al₂O₃ catalyst can be attributed to the structural characteristic that large amounts of uniform-sized small (7.2 ± 0.9 nm) Ni particles are highly dispersed into porous alumina matrix. The aggregation of active metallic Ni particles during the high temperature reaction can be effectively prevented by the porous alumina matrix due to the strong interaction between them, thus ensuring a good catalytic performance.     

Preparation of Ni/Pt catalysts supported on spinel (MgAl2O4) for methane reforming

MgAl₂O₄ was synthesized through hydrolysis of metallic alkoxides of Mg²⁺ and Al³⁺. The formed spinel precursor phase was calcined at temperatures between 600 and 1100 °C, for 4 h. The spinel was utilized as a Ni/Pt catalyst support. The Ni/MgAl₂O₄ catalysts (15% Ni, w/w) containing small amounts of Pt were tested for methane steam reforming. The solids were analyzed by X-ray diffraction (XRD), temperature programmed reduction (TPR) with H₂ and catalytic tests. The spinel phase was formed at temperatures above 700 °C. The addition of small amounts of Pt to Ni/MgAl₂O₄ promoted an increase in surface area. This probably caused the considerable increase in methane conversion.     

Ni nanoparticles supported on mica for efficient decomposition of ammonia to COx-free hydrogen

A wet impregnation method is used to synthesize Ni nanocatalysts supported on naturally abundant mica nanosheets for decomposition of ammonia to CO_x-free hydrogen. The prepared catalysts are characterized by XRD, SEM, TEM, N₂ sorption, TG, XPS, H₂-TPR and NH₃/H₂-TPD techniques. The catalytic tests exhibit that the Ni/mica catalysts are highly active for ammonia decomposition. The two-dimensional structure of mica favors mass transportation, which can remarkably promote the catalytic process. The NH₃/H₂-TPD curves of Ni/mica show no desorption signals of NH₃ and H₂, indicating the presence of weak desorption energy barrier. The content of Ni in the catalysts is related to the crystallite size of Ni species, affecting their catalytic properties. As demonstrated in this study, the Ni/mica catalyst with 15% Ni loading amount exhibits the highest catalytic activity and long-term stability. At a high space velocity of 30000 cm³ g_cat^?1 h^?1, 97.2% ammonia conversion is achieved over the 15%Ni/mica catalyst at 650 °C, indicating the Ni/mica is a promising catalyst for ammonia decomposition.     

Ni/La2O3 and Ni/MgO–La2O3 catalysts for the decomposition of NH3 into hydrogen

The decomposition of NH₃ for hydrogen production was studied using Ni/La₂O₃ catalysts at varying compositions and temperatures prepared via surfactant-templated synthesis to elucidate the influence of catalyst active metal content, support composition and calcination temperature on the catalytic activity. The catalytic performance of all samples was studied between 300 and 600 °C under atmospheric pressure. The catalytic activity of the sample were as follows: 10Ni/La₂O₃-450 > 10Ni/La₂O₃-550 > 10Ni/La₂O₃-650 ≈ 10Ni/La₂O₃-750 ≈ 10Ni/La₂O₃-850. The excellent activity (100%) of 10Ni/La₂O₃-450 could be due to the high surface area, basicity strength and concentration of surface oxygen species of the catalyst as evidenced by BET, CO₂-TPD and XPS. In addition, to adjust the activity of the catalyst support, the molar ratios of Mg and La were varied (1:1, 3:1, 5:1, 7:1 and 9:1). The 5Ni/5MgLa (5:1 M ratio) was found to be the most active (100%) relative to other Ni/MgLa formulations. Furthermore, the Ni content in the Ni/5MgLa sample was adjusted between 10 and 40 wt%. Increasing the Ni content of the catalysts increased NH₃ conversion with the 40 wt% Ni formulation demonstrating complete NH₃ conversion at 600 °C and a high gas hourly space velocities (GHSV) (30,000 mL∙h⁻¹∙g_cat⁻¹).     

Copper-based catalysts over A520-MOF derived aluminum spinels for hydrogen production by methanol steam reforming: The role of spinal support on the performance

Spinel materials can be appropriate candidates for supporting the catalysis domain because of several properties, such as high thermal stability and porous structure. In this work, MAl₂O₄ spinels (M: Ni, Co, Zn, and Mg) are prepared using commercial A520 (Al-MOF) and M(NO₃)₂·6H₂O (M: Ni, Co, Zn, and Mg) at 750 °C. The prepared spinels are applied to support Cu active metal in the methanol steam-reforming (MSR) reaction. The fabricated catalysts are characterized comprehensively by X-ray powder diffraction (XRD), energy-dispersive X-ray analysis (EDX), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), temperature-programmed reduction (H₂-TPR), temperature-programmed desorption (NH₃-TPD), and BET surface area analysis (S_BET). An extensive study of the MSR process using microstructure monolith/MAl₂O₄/Cu catalysts is accomplished in the range of 150–300 °C. High methanol conversion, good H₂ selectivity, and lower CO selectivity are obtained for Cu/MgAl₂O₄ among all prepared catalysts. The TEM micrograph for Cu/MgAl₂O₄ demonstrates platelet morphology at an average size of ~50 nm. Based on thermal analysis, the amount of coke deposited on four spent catalysts after 30 h on stream at 200 °C is less than 1%.     

Catalytic CO2 reforming of CH4 over MgAl2O4 supported Ni-Co catalysts for the syngas production

Ni, Co and Ni–Co bimetallic catalysts of different ratios were synthesized by the Incipient Wetness Impregnation Method (IWI) over Magnesium Aluminate support, keeping the total metal loading 15 wt.%, characterized and tested for the reforming of methane with carbon dioxide at 873 K and 1 atm pressure. Magnesium Aluminate supported catalysts were also compared with Al₂O₃ supported Ni catalysts with similar metal loading. The results obtained revealed that MgAl₂O₄ exhibited excellent thermal stability as compared to Al₂O₃ as support at higher temperatures. Ni–Co catalyst, with an explicit Ni:Co (3:1) ratio for the 75Ni25Co/MgAl₂O₄ provided the highest CH₄ conversion and was about 1.82 times that of the 100Ni/MgAl₂O₄; CO₂ conversion also followed similar trends. Co-existence of Ni and Co with synergic effect in an explicit Ni:Co (3:1) ratio reduced the reduction temperature and increased the amount of metal in 75Ni25Co/MgAl₂O₄. CH₄ and CO₂ conversions, TOF_DRM, H₂: CO ratios and catalyst deactivations were related to the concentrations of the Ni–Co and particularly an explicit ratio of 3:1 for the Ni:Co in 75Ni25Co/MgAl₂O₄ catalyst provided the best initial & final conversions, TOF_DRM and H₂:CO ratio. Detail carbon analysis suggested that the type of coke deposited on 75Ni25Co/MgAl₂O₄ after the DRM reaction is of the same nature and are originating from the CH₄ cracking reaction and are of reactive type.     

Effect of O2 and temperature on the catalytic performance of Ni/Al2O3 and Ni/MgAl2O4 for the dry reforming of methane (DRM)

Al₂O₃ and MgAl₂O₄ supported 10% (w/w) Ni catalysts having a dispersion of 1.5 and 2.0% are active for DRM at 600 and 750 °C. High temperature reduction of both the calcined catalysts resulted in metallic Ni being formed, suggesting strong support metal interactions. The CH₄ and CO₂ conversion during DRM are relatively constant with time-on-stream, and are higher for Ni/MgAl₂O₄ than Ni/Al₂O₃. Carbon-whiskers are also detected on both catalysts. O₂ co-feed of 2.6% (v/v) and increasing reaction temperature to 750 °C helped in decreasing the amount of carbon deposited, except for Ni/MgAl₂O₄ at 600 °C. Furthermore, higher conversions and H₂/CO ratios are achieved. It appears that on spent Ni/MgAl₂O₄ a different type of carbon species was formed, and this carbon species was difficult to remove by oxygen at 600 °C. Thus, co-feeding O₂, using an appropriate temperature, and choosing a suitable support can reduce the carbon present on the nickel catalysts during DRM.     

Plasma-catalytic ammonia decomposition using a packed-bed dielectric barrier discharge reactor

Plasma-catalytic ammonia decomposition as a method for producing hydrogen was studied in a packed-bed dielectric barrier discharge (DBD) reactor at ambient pressure and a fixed plasma power. The influence of packing the plasma zone with various dielectric materials, typically used as catalyst supports, was examined. At conditions (21 W, 75 Nml/min NH₃) where an NH₃ conversion of 5% was achieved with plasma alone, an improved decomposition was found when introducing dielectric materials with dielectric constants between 4 and 30. Of the tested materials, MgAl₂O₄ yielded the highest conversion (15.1%). The particle size (0.3–1.4 mm) of the MgAl₂O₄ packing was found to have a modest influence on the conversion, which dropped from 15.1% to 12.6% with increasing particle size. Impregnation of MgAl₂O₄ with different metals was found to decrease the NH₃ conversion, with the Ni impregnation still showing an improved conversion (7%) compared to plasma-only. The plasma-assisted ammonia decomposition occurs in the gas phase due to micro-discharges, as evident from a linear correlation between the conversion and the frequency of micro-discharges for both plasma alone and with the various solid packing materials. The primary function of the solid is thus to facilitate the gas phase reaction by assisting the creation of micro-discharges. Lastly, insulation of the reactor to raise the temperature to 230 °C in the plasma zone was found to have a negative effect on the conversion, as a change from volume discharges to surface discharges occurred. The study shows that NH₃ can be decomposed to provide hydrogen by exposure to a non-thermal plasma, but further developments are needed for it to become an energy efficient technology.     

H2SO4 poisoning of Ru-based and Ni-based catalysts for HI decomposition in SulfurIodine cycle for hydrogen production

The sulfur–iodine (SI) cycle is deemed to be one of the most promising alternative methods for large-scale hydrogen production by water splitting, free of CO₂ emissions. Decomposition of hydrogen iodide is a pivotal reaction that produces hydrogen. The homogeneous conversion of hydrogen iodide is only 2.2% even at 773 K [1]. A suitable catalyst should be selected to reduce the decomposition temperature of HI and attain reaction yields approaching to the thermodynamic equilibrium conversion. However, residual H₂SO₄ could not be avoided in the SI cycle because of incomplete purification. The H₂SO₄ present in the HI feeding stream may lead to the poisoning of HI decomposition catalysts. In this study, the activity and sulfur poisoning of Ru and Ni catalysts loaded on carbon and alumina, respectively, were investigated at 773 K. HI conversion efficiency markedly decreased from 21% to 10% with H₂SO₄ (3000 ppm) present, which was reversible when H₂SO₄ was withdrawn in the case of Ru/C. In the case of Ru/C and Ni/Al₂O₃, catalyst deactivation depends on the concentration of H₂SO₄; the higher the concentration of H₂SO_4, the greater the severity of deactivation. Catalysts before and after sulfur poisoning were characterized by transmission electron microscopy (TEM), energy-dispersive X-Ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Experimental results and characterization of poisoned and fresh catalysts indicate that the catalyst deactivation could be ascribed to the competitive adsorption of sulfur species and change in its surface properties.     

Preparation and characterization of Ni based catalysts for the catalytic partial oxidation of methane: Effect of support basicity on H2/CO ratio and carbon deposition

The catalytic partial oxidation of methane (CPOM) was studied on Ni based catalysts. Catalysts were prepared by wet impregnation method and characterized by using AAS, BET, XRD, HRTEM, TPR, TPO, Raman Spectroscopy and TPSR techniques. The prepared catalysts showed nearly 95% CH₄ conversion and nearly 96% H₂ selectivity under the flow of 157,500 (L kg⁻¹ h⁻¹) with the ratio of CH₄/O₂ = 2 by using air as an oxidant at 1 atm and 800 °C. Support basicity greatly influenced the H₂/CO ratio and carbon deposition. It was found that the lowest carbon deposition occurred on Ni impregnated MgO catalyst. Considering the results, it was found that Ni/MgO catalyst with 10% Ni content would be the best catalyst amongst Ni/Al₂O₃, Ni/MgO/Al₂O₃, Ni/MgAl₂O₄ and Ni/Sorbacid for the CPOM only under more reductive conditions. Under optimum conditions, Ni/MgO showed poor performance and therefore Ni/Sorbacid would be the ideal catalyst because of its greater carbon resistance than the other catalysts.     

Production of hydrogen by methane dry reforming over ruthenium-nickel based catalysts deposited on Al2O3, MgAl2O4, and YSZ

In this work, monometallic (1 wt% of Ru or 5 wt% of Ni) and bimetallic catalysts (1 wt% Ru-5 wt.% Ni) deposited on alumina (Al₂O₃), magnesium aluminate spinel (MgAl₂O₄), and yttria-stabilized zirconia (YSZ) were prepared by wet impregnation. The synthesis method of MgAl₂O₄ was optimized and a well crystallized phase with high specific surface area was obtained by using wet impregnation, as a simple and low cost route, at 800 °C for 2 h.The catalytic activity was compared at atmospheric pressure and 750 °C toward methane dry reforming (DRM) reaction with a molar ratio CH₄/CO₂ = 1/1 and a Weight Hourly Space Velocity (WHSV) of 60.000 mL g⁻¹.h⁻¹.Catalytic activity classification was obtained as the following: Ni/MgAl₂O₄ > Ru-Ni/Al₂O₃ > Ru-Ni/MgAl₂O₄ > Ru-Ni/YSZ > Ni/Al₂O₃ > Ni/YSZ > Ru/Al₂O₃ > Ru/YSZ » Ru/MgAl₂O₄. Between the different catalysts, 5 wt% Ni/MgAl₂O₄ catalyst exhibited excellent catalytic activity for DRM. Furthermore, this catalyst was found to be very stable without any deactivation after 50 h under reacting mixture with a low carbon formation rate (3.58 mg_C/g_cat/h). Such superior activity and stability of MgAl₂O₄ supported Ni catalyst is consistent with characterization results from BET, XRD, TPR, CO-pulse chemisorption and CHNS analysis. It can be due to a strong interaction between Ni and MgAl₂O₄ leading to the incorporation of Ni into the spinel lattice and the formation of oxygen vacancies offering a benefit for DRM reaction.Furthermore, it seems that the addition of ruthenium onto Ni/MgAl₂O₄ decreases the interaction between Ni and the spinel leading to a decrease in the catalyst performance. On the other side, the addition of ruthenium on Ni/Al₂O₃ leads to an increase in the catalyst stability and efficiency by inhibiting the formation of poorly active phase NiAl₂O₄ already observed in TPR.     

Combined pre-reformer/reformer system utilizing monolith catalysts for hydrogen production

The pre-reforming of higher hydrocarbon, propane, was performed to generate hydrogen from LPG without carbon deposition on the catalysts. A Ru/Ni/MgAl₂O₄ metallic monolith catalyst was employed to minimize the pressure drop over the catalyst bed. The propane pre-reforming reaction conditions for the complete conversion of propane with no carbon formation were identified to be the following: space velocities over 2400 h⁻¹ and temperatures between 400 and 450 °C with a H₂O/C₁ ratio of 3. The combined pre-reformer and the main reformer system with the Ru/Ni/MgAl₂O₄ metallic monolith catalyst was employed to test the conversion propane to syngas where the reaction heat was provided by catalytic combustors. Propane was converted in the pre-reformer to 52.5% H₂, 27.0% CH₄, 17.5% CO, and 3.0% CO₂ with a 331 °C inlet temperature and a 482 °C catalyst outlet temperature. The main steam reforming reactor converted the methane from the pre-reformer with a conversion of higher than 99.0% with a 366 °C inlet temperature and an 824 °C catalyst outlet temperature. With a total of 912 cc of the Ru/Ni/MgAl₂O₄ metallic monolith catalyst in the main reformer, the H₂ production from the propane reached an average of 3.25 Nm³h⁻¹ when the propane was fed at 0.4 Nm³h⁻¹.     

Bimetallic NixCo10-x/CeO2 as highly active catalysts to enhance mid-temperature ammonia decomposition: Kinetics and synergies

Catalytic ammonia decomposition is an attractive method to generate hydrogen at mid-temperatures (<700 °C) but must incorporate precious metals (Pd, Ru, etc.) to ensure high reactivity. Developing Ni-based catalysts to decompose ammonia can enhance its prospect for hydrogen generation. However, the catalytic activity of Ni is hardly satisfactory at mid-temperatures. In this work, we show the bimetallic Ni_xCo_10-x/CeO₂ towards mid-temperature NH₃ decomposition, with the metal loading of Ni and Co tuned. Kinetics study demonstrates that the NH₃ decomposition reaction follows the Temkin Pyzhev mechanism and the synergy between Ni and Co can decrease the reaction orders regarding NH₃ and increase the reaction orders regarding H₂. Mechanistic results indicate that the recombinative N desorption limits the reaction rate. The synergy between Ni and Co can simultaneously decrease the energy barriers of the recombinative N desorption and mitigate the H₂ poisoning effect. Therefore, Ni_7.5Co_2.5/CeO₂ displays both high ammonia conversion (96.96%) and hydrogen formation rate (1947.9 mmol/(g_cat.h)) at 650 °C. We hope the mechanism in this work can be used to guide the design of inexpensive catalysts to decompose ammonia at mid-temperatures.     

Methane tri-reforming for synthesis gas production using Ni/CeZrO2/MgAl2O4 catalysts: Effect of Zr/Ce molar ratio

Three Ni/CeZrO₂/MgAl₂O₄ catalysts synthesized using different Zr/Ce molar ratios (0.25, 1, and 4) were studied for methane tri-reforming. The catalysts were characterized using XRD, ²⁷Al-NMR, H₂-TPR, CO₂-TPD, XPS, and in situ techniques (XPD and XANES). The addition of CeZrO₂ at Zr/Ce = 0.25 on the MgAl₂O₄ spinel support considerably reduced the amount of carbon deposits, because the methane decomposition reaction was attenuated by the presence of less agglomerated Ni⁰ species produced after the reduction process. The highest CO₂ adsorption capacity (basicity) was associated with the participation of medium-strength basic sites, which facilitated coke gasification and led to higher CO₂ conversions. A syngas with quality (H₂/CO ratio) of 1.8 was produced, suitable for use in Fischer-Tropsch reactions.     

Ammonia decomposition over nickel catalysts supported on alkaline earth metal aluminate for H2 production

The Ni catalysts supported on alkaline earth metal aluminate compounds, Ni/AM-Al-O (AM = Mg, Ca, Sr, Ba) were synthesized to investigate the influence of their basic property on NH₃ decomposition activity. The basic strength of the catalysts was confirmed to correspond to that of added alkaline earth metal in the support materials (Ni/Mg–Al–O < Ni/Ca–Al–O < Ni/Sr–Al–O < Ni/Ba–Al–O) from CO₂-TPD measurement. This basic strength of the catalysts could influence the catalytic activity for NH₃ decomposition, which increased in order of the Ni/Mg–Al–O < Ni/Ca–Al–O < Ni/Sr–Al–O < Ni/Ba–Al–O catalysts. NH₃-TPSR showed that the strong basic property weakened H₂ adsorption but slightly strengthened N₂ adsorption for the catalysts except for the Ni/Mg–Al–O catalyst. From the kinetic analysis, the absolute value of the H₂ reaction order decreased with increasing basic strength of the catalysts, indicating that the strong basic property of the catalysts could alleviate the H₂ inhibition in ammonia decomposition.     

Enhanced hydrogen permeance through graphene oxide membrane deposited on asymmetric spinel hollow fiber substrate

Membranes of graphene oxide (GO) present suitable application for hydrogen (H₂) purification. The deposition of a selective and high permeable GO membrane on a proper substrate is still a challenge. Here we applied the vacuum-assisted method to deposit a GO layer on asymmetric spinel (MgAl₂O₄) hollow fibers. The synthetized GO showed a nanosheeted morphological structure and a relative high degree of oxidation. The hollow fibers were produced with dolomite and alumina as the ceramic starting material and showed the desired asymmetric pore size distribution, in addition to suitable bending strength, 54.88 ± 4.25 MPa, and average surface roughness, 180 ± 8.2 nm. A continuous GO layer of 1.7 ± 0.2 μm was deposited onto the fiber outer surface. The composite MgAl₂O₄/GO membrane presented H₂ permeance of 8.2 ± 0.0 × 10^?7 mol s^?1 m^?2 Pa^?1 at room temperature (approximately 25 °C) and 0.3 MPa of transmembrane pressure. Ideal hydrogen/nitrogen and hydrogen/carbon dioxide selectivity values were of 3.3 ± 0.0 and 11.4 ± 0.1, respectively.     

Ni supported on MgO modified attapulgite as catalysts for hydrogen production from glycerol steam reforming

A series of Mg-modified Ni/Attapulgite (ATP) catalysts have been prepared by impregnation method for glycerol steam reforming to produce hydrogen. The physicochemical properties of catalysts were characterized using various techniques including N₂ physical adsorption analysis, XRD, H₂-TPR, SEM, TEM and NH₃-TPD. The results of N₂ physical adsorption indicated MgO modified Ni-based catalysts had unique mesostructure, resulting in the high metal dispersion and interaction between active metal and support as proven by XRD, TEM and H₂-TPR. Results of glycerin reforming experiments showed that Ni/10MgO/ATP catalyst had the highest activity than that of the other catalysts. Ni/10MgO/ATP catalyst had the smallest Ni average crystal size (10.1 nm) and the highest surface area (110.31 m²/g). These excellent properties made it show the enhanced glycerol conversion (94.71%) and a higher H₂ yield (88.45%) and the longest stability (30 h) during glycerol steam reforming (GSR) at 600 °C, W/G = 3, and WHSV = 1 h^?1. The used catalysts after 60 h of glycerin reforming experiments were also investigated by XRD, SEM, TEM, Roman and TG-DTG. The results indicated that the addition of Mg significantly inhibited the sintering of nickel grains and the formation of amorphous carbon. Therefore, Ni/10MgO/ATP catalyst increased the activity of the catalyst and extended the life of the catalyst.     

Current advances in syngas (CO + H2) production through bi-reforming of methane using various catalysts: A review

Today, bi - reforming of methane is considered as an emerging replacement for the generation of high-grade synthesis gas (H₂:CO = 2.0), and also as an encouraging renewable energy substitute for fossil fuel resources. For achieving high conversion levels of CH₄, H₂O, and CO₂ in this process, appropriate operation variables such as pressure, temperature and molar feed constitution are prerequisites for the high yield of synthesis gas. One of the biggest stumbling blocks for the methane reforming reaction is the sudden deactivation of catalysts, which is attributed to the sintering and coke formation on active sites. Consequently, it is worthwhile to choose promising catalysts that demonstrate excellent stability, high activity and selectivity during the production of syngas. This review describes the characterisation and synthesis of various catalysts used in the bi-reforming process, such as Ni-based catalysts with MgO, MgO–Al₂O₃, ZrO_2, CeO₂, SiO₂ as catalytic supports. In summary, the addition of a Ni/SBA-15 catalyst showed greater catalytic reactivity than nickel celites; however, both samples deactivated strongly on stream. Ce-promoted catalysts were more found to more favourable than Ni/MgAl₂O₄ catalyst alone in the bi-reforming reaction due to their inherent capability of removing amorphous coke from the catalyst surface. Also, Lanthanum promoted catalysts exhibited greater nickel dispersion than Ni/MgAl₂O₄ catalyst due to enhanced interaction between the metal and support. Furthermore, La₂O₃ addition was found to improve the selectivity, activity, sintering and coking resistance of Ni implanted within SiO₂. Non-noble metal-based carbide catalysts were considered to be active and stable catalysts for bi-reforming reactions. Interestingly, a five-fold increase in the coking resistance of the nickel catalyst with Al₂O₃ support was observed with incorporation of Cr, La₂O₃ and Ba for a continuous reaction time of 140 h. Bi-reforming for 200 h with Ni-γAl₂O₃ catalyst promoted 98.3% conversion of CH₄ and CO₂ conversion of around 82.4%. Addition of MgO to the Ni catalyst formed stable MgAl₂O₄ spinel phase at high temperatures and was quite effective in preventing coke formation due to enhancement in the basicity on the surface of catalyst. Additionally, the distribution of perovskite oxides over 20 wt % silicon carbide-modified with aluminium oxide supports promoted catalytic activity. NdCOO₃ catalysts were found to be promising candidates for longer bi-reforming operations.     

Synergistic coupling of CoFe-layered double hydroxide nanosheet arrays with reduced graphene oxide modified Ni foam for highly efficient oxygen evolution reaction and hydrogen evolution reaction

Novel CoFe-LDH (layered double hydroxide) nanosheet arrays in situ grown on rGO (reduced graphene oxide) uniformly modified Ni foam were synthesized by a citric acid-assisted aqueous phase coprecipitation strategy. Systematic characterizations indicates that the series of Co_xFe₁-LDH/rGO/NF (x = 4, 3, 2) all show Co_xFe₁-LDH nanosheets (150–180 × 15 nm) grown vertically on the surface of rGO/NF. Especially, the Co₃Fe₁-LDH/rGO/NF exhibits the best performance with overpotentials of 250 and 110 mV at 10 mA cm^?2 in 1 M KOH for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. When it is used as cathode and anode simultaneously for overall water splitting, they require 1.65 and 1.84 V at 10 and 100 mA cm^?2, respectively. Excellent performance of Co₃Fe₁-LDH/rGO/NF is due to the nanosheet arrays structure with open channels, synergistic coupling between Co₃Fe₁-LDH and rGO enhancing electrical conductivity, and in-situ growth of Co₃Fe₁-LDH on rGO/NF enhancing stability.     

High-surface-area Ce0.8Zr0.2O2 solid solutions supported Ni catalysts for ammonia decomposition to hydrogen

Three kinds of Ce_0.8Zr_0.2O₂ solid solutions synthesized via surfactant-assisted route, co-precipitation, and sol–gel method were used as supports of Ni-based catalysts by impregnation. Their catalytic activities in ammonia decomposition to hydrogen were tested, and the structural effect of support and the influence of nickel content on catalytic activity were evaluated. Mesoporous/high-surface-area Ce_0.8Zr_0.2O₂ support synthesized by surfactant-assisted method exhibited better promoting effect than other supports when the same content of Ni was loaded. The interactions between Ni species and Ce_0.8Zr_0.2O₂ supports were found to greatly affect the chemical properties of catalysts, including redox, H₂ adsorption, and catalysis. The promoting effects of Ce in catalysts, plentiful vacancies in the solid solutions due to the doping of Zr⁴⁺, and high surface areas of the supports were discussed on the ammonia decomposition activities of the resultant catalysts, as well as the influence of hydrogen spillover. The ammonia conversion of 95.7% with the H₂ producing rate of 89.3 mL/min·g_cat was achieved at 550 °C over the Ni catalysts supported on the mesoporous/high-surface-area Ce_0.8Zr_0.2O₂.