Tri-metallic Ni–Co modified reducible TiO2 nanocomposite for boosting H2 production through steam reforming of phenol

Well-designed Co₃O₄ nanocubes (NCs) dispersed NiO/TiO₂ to construct tri-metallic reducible NiO/TiO₂/Co₃O₄ NCs structured catalyst for steam-reforming of phenol (SRP) with enhanced hydrogen production has been investigated. The controlled morphology with good dispersion was obtained, enabling efficient SRP toward selective H₂ production. Using 10% NiO- 5% Co₃O₄ NCs/TiO₂ composite, H₂ yield of 69.91% and phenol conversion of 78.4% was achieved, significantly higher than using NiO/TiO₂ and TiO₂ samples. The cubical structured Co₃O₄ dispersed NiO/TiO₂ composite showed significantly improved H₂ yield and phenol conversion due to strong metal-support interaction with reducible support for providing more active sites. The H₂ production was further increased by increasing reaction temperature, phenol concentration, feed flow rate and catalysts loading, however, they have adverse effect on the selectivity due to more CO formation. The composite catalyst possesses excellent activity and stability due to strong tri-metallic interaction and exceptional electronic interfaces. The spent catalyst analysis confirms the formation of graphene and carbon nanotubes over the reducible support. This study reveals that Co₃O₄ NCs are able to increase NiO/TiO₂ activity for H₂ production by inhibiting carbon monoxide formation and would be beneficial in other reforming applications.     

Fabrication of direct Z-scheme MoO3/N–MoS2 photocatalyst for synergistically enhanced H2 production

A novel visible-light active MoO₃/N–MoS₂ heterostructure photocatalyst was fabricated via hydrothermal process. The structure, morphology and optical characteristics were studied using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), UV–visible and photoluminescence (PL) spectroscopies. The results indicated that loading pf MoO₃ and nitrogen doping played main influence role in advancing the morphology and optical characteristics. Upon visible photo-illumination, the MoO₃/N–MoS₂ sample displayed superior photocatalytic H₂-production activity (118 μ mol h⁻¹g⁻¹), which was about four-time higher than that of pure MoS₂ (30 μ mol h⁻¹g⁻¹). The enhancement in photocatalytic performance of MoO₃/N–MoS₂ photocatalyst can be ascribed to the development of direct Z-scheme heterostructure, which promoted the photo-excited electrons/holes transfer and separation. The recycling experiment verified that the MoO₃/N–MoS₂ photocatalyst had superior cyclic activity and stability, implying promising applications in energy field.     

Preparation and application of binary acid–base CaO–La2O3 catalyst for biodiesel production

A simple method was developed for biodiesel production from non-edible Jatropha oil which contains high free fatty acid using a bifunctional acid–base catalyst. The acid–base catalyst comprising CaO and La₂O₃ mixed metal oxides with various Ca/La atomic ratios were synthesized via co-precipitation method. The effects of Ca/La compositions on the surface area, acidity–basicity and transesterification activity were investigated. Integrated metal–metal oxide between Ca and La enhanced the catalytic activity due to well dispersion of CaO on composite surface and thus, increased the surface acidic and basic sites as compared to that of bulk CaO and La₂O₃ metal oxide. Furthermore, the transesterification reactions resulted that the catalytic activity of CaO–La₂O₃ series were increased with Ca/La atomic ratio to 8.0, but the stability of binary system decreased by highly saturated of CaO on the catalyst surface at Ca/La atomic ratio of 10.0. The highest biodiesel yield (98.76%) was achieved under transesterification condition of 160 °C, 3 h, 25 methanol/oil molar ratio and 3 wt.%. In addition, the stability of CaO–La₂O₃ binary system was studied. In this study, Ca–La binary system is stable even after four cycles with negligible leaching of Ca²⁺ ion in the reaction medium.     

H2O2-assisted preparation of microspherical C60–TiO2 photocatalyst and its hydrogen evolution mechanism

Photocatalytic water splitting to produce hydrogen is one of the promising methods to deal with energy shortage and environmental crisis. In this paper, n-type H₂O₂/C₆₀–TiO₂ photo-catalysts with excellent hydrogen production performance were prepared by simple hydrothermal method. The prepared catalysts were characterized by polycrystalline XRD, TEM, UV–Vis–NIR spectroscopy, X-ray photoelectron spectroscopy, FTIR spectroscopy, Raman spectroscopy, etc. The results showed that H₂O₂ can promote the formation of microspherical catalyst; meanwhile, fullerene can broaden the light response range, increase the separation ability of photogenerated carriers and catalyze the formation of molecular H₂ due to the formed superoxide radical. The water splitting experiments showed that the hydrogen evolution rate of H₂O₂/C₆₀–TiO₂ is up to 41.6 mmol?g^?1h^?1, 9.7 times of pure TiO₂. These results have important reference significance for the development of new photocatalysts for water splitting to produce hydrogen.     

Improved hydrogen production performance of Ni–Al2O3/CaO–CaZrO3 composite catalyst for CO2 sorption enhanced CH4/H2O reforming

Bifunctional composite catalysts are very intrigued to produce hydrogen via CO₂ sorption enhanced CH₄/H₂O reforming. However, their hydrogen production performance declined over multiple cycles, owing to the structure collapse and the sintering of active component under high-temperature regeneration. This work reported the facile synthesis of long-lasting Ni–Al₂O₃/CaO–CaZrO₃ composite catalysts with less inert components (36 wt%) for stable hydrogen production over the multiple cycles of CO₂ sorption enhanced CH₄/H₂O reforming. The effects of reaction and regeneration temperature on the hydrogen production performance of Ni–Al₂O₃/CaO–CaZrO₃ were explored. Ni–Al₂O₃/CaO–CaZrO₃ demonstrated high activity and stability while fixing reaction temperature as 600 °C and regeneration temperature as 750 °C. Of particular importance, H₂ concentration was 98 vol% even after 10 hydrogen production cycles due to the inert component CaZrO₃ having a cross-linked structure. The distribution of CaZrO₃ in the composite as a coral-like structure inhibited the sintering of CaO through high Taman temperature and physical separation. Moreover, it provided the skeleton support and pore volume for the repeated expansion and contraction process of CaO to CaCO₃ during the cycling process. Finally, the sintering of Ni slowed down in appropriate regeneration temperature to maintain the structure of the composite catalyst, which further improved the catalyst's stability over multiple cycles.     

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.     

Tuning of electrocatalytic activity of WO3–TiO2 nanocomposite electrode for alkaline hydrogen evolution reaction

The study reports the synthesis of mesoporous WO₃–TiO₂ nanocomposite with tuned particle size (~7 nm), pore diameter (~4.9 nm), specific surface area (S_BET = 129.112 m²/g) and pore volume (V_tot = 0.185 cm³/g) by an acid catalyzed peptization method, and its utilization for the development of stable catalytic electrode with enhanced activity towards alkaline hydrogen evolution reaction (HER). The SEM and AFM analyses confirm the formation of good quality composite electrodes with improved surface roughness through electroless deposition method. The developed WO₃–TiO₂ nanocomposite electrode exhibits low overpotential value of 120 mV with an exchange current density of 6.20 × 10^?5 mA/cm², and a low Tafel slope value of 98 mV/dec. Apart from the high HER performance, the developed WO₃–TiO₂ nanocomposite electrode exhibits competency with the state-of-the-art electrode materials for alkaline HER in industrial processes with sustained catalytic activity, tolerance behavior and long-term stability.     

Thermodynamic models for H2O–CO2–H2 mixtures in near-critical and supercritical regions of water

The PVTx properties of the H₂O–CO₂–H₂ mixtures have significant applications in the technology of supercritical water gasification of coal. Here, we first carry out the molecular dynamics simulations of the PVTx properties of the H₂O–CO₂–H₂ mixtures in the near-critical and supercritical regions of water to generate 600 datasets at 750–1150 K and 4.0–443.5 MPa. The molar fraction of each composition in the ternary mixtures ranges from 10% to 80%. Later we investigate the applicability of a well-known thermodynamic model for the ternary mixtures, namely the Duan-Møller-Weare equation of state (DMW EOS). It is observed that the DMW EOS shows great potential in the prediction of the PVTx properties of the ternary mixtures. However, it is noted that the mixing parameters describing the binary interactions of H₂O–H₂ and CO₂–H₂ are still unknown in the DMW EOS. By determining the missing mixing parameters using the Levenberg-Marquardt algorithm, the accuracy of the original DMW EOS is improved for the ternary mixtures. Moreover, optimizing the coefficients in the DMW EOS further promotes the accuracy of the model for the H₂O–CO₂–H₂ mixtures. The results from this work may facilitate the development of supercritical water gasification of coal.     

H2 production of (CdS–ZnS)–TiO2 supported photocatalytic system

Mixed semiconductor (CdS–ZnS)–TiO₂(1 : 1 : 1) mixture system over different supports like MgO, CaO, γ-Al₂O₃, SiO₂ and modified MgO and CaO, have been prepared, characterized and tested for H₂ production in a S²⁻⧸SO²⁻₃ mixture solution. (CdS–ZnS)–TiO₂(D) over MgO support wherein the TiO₂ taken is from Degussa (D) sample gives 206.7 μmol⧸h of H₂ production and this catalyst sustain the H₂ production rate for longer durations. Dopants like Li₂O, Cs₂O or K₂O make MgO and CaO supports act like super basic oxide when they are doped and in turn increase the photocatalytic activity. The (CdS–ZnS)–TiO₂(I) system wherein the TiO₂ taken from Titanium Isopropoxide, supported on 20 wt% Li₂O doped CaO is found to give 209.8 μmol⧸h rate of H₂ production. Characterization studies like UV-Visible spectra, X-ray Diffraction spectra and Scanning Electron Microscope photographs were taken for all the catalysts and the data generated over these samples is evaluated. A scheme of H₂S photocatalytic decomposition of ZnCdS–TiO₂(D⧸I) over different supports in the presence of S²⁻⧸SO²⁻₃ substrate, is proposed indicating the formation of thiosulfate cycle at this heterojunction. © 1999 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.     

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).     

Catalytic steam reforming of glycerol over Ni–La2O3–CeO2/SBA-15 catalyst for stable hydrogen-rich gas production

Ni-based catalysts (Ni, Ni–La₂O₃, and Ni–La₂O₃–CeO₂) on mesoporous silica supports (SBA-15 and KIT-6) were prepared by an incipient wetness impregnation and tested in glycerol steam reforming (GSR) for hydrogen-rich gas production. The catalysts were characterized by the N₂-physisorption, TPD, X-ray diffraction (XRD), SEM-EDS, and TEM techniques. N₂-physisorption results of calcined catalysts highlight that adding of La₂O₃ increased surface area of the catalyst by preventing pore mouth plugging in SBA-15, which was frequently observed due to the growth of NiO crystals. A set of GSR experiments over the catalysts were performed in an up-flow continuous packed-bed reactor at 650 °C and atmospheric pressure. The highest hydrogen concentration of 62 mol% was observed with a 10%Ni–5%La₂O₃ –5%CeO₂/SBA-15 catalyst at a LHSV of 5.8 h⁻¹. Adding of CeO₂ to the catalyst appeared to increase catalytic stability by facilitating the oxidative gasification of carbon formed on/near nickel active sites of Ni–La₂O₃–CeO₂/SBA-15 and Ni–La₂O₃–CeO₂/KIT-6 catalyst during the glycerol steam reforming reaction.     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Modeling study of hydrogen production via partial oxidation of H2S–H2O blend

Kinetic analysis of the thermal partial oxidation in the H₂S–H₂O–O₂(air) mixture in a flow reactor with given length is conducted numerically on the basis of developed reaction mechanism. This mechanism incorporates the reaction paths typical both for the H₂S pyrolysis and for the H₂S oxidation and describes with reasonable accuracy a large set of experimental data. The computations have demonstrated that addition of H₂O to the fuel-rich H₂S–O₂(air) mixture allows one to increase the relative yield of H₂ in the conversion products. At identical fractions of H₂S and H₂O in the H₂S–H₂O blend the increase in the H₂ relative yield can mount to a factor of 1.5. Though the addition of H₂O to H₂S leads to the delay of the conversion of H₂S, nevertheless, at initial temperature (T₀ = 1000 K) it is possible to occur the conversion process in a shot flow reactor of 1 m length at atmospheric pressure. It has been shown that the formation of additional amount of H₂ in the conversion products upon the H₂O admixture to H₂S is caused by the increase of the role of reaction H₂O + H = OH + H₂. The growth in the initial temperature of the H₂S–H₂O–O₂(air) mixture increases the absolute concentration of H₂ in the conversion products and its relative yield.     

A comparative study of Ni catalysts supported on Al2O3, MgO–CaO–Al2O3 and La2O3–Al2O3 for the dry reforming of ethane

CO₂ utilization through the activation of ethane, the second largest component of natural and shale gas, to produce syngas, has garnered significant attention in recent years. This work provides a comparative study of Ni catalysts supported on alumina, alumina modified with CaO and MgO, as well as alumina modified with La₂O₃ for the reaction of dry ethane reforming. The calcined, reduced and spent catalysts were characterized employing XRD, N₂ physisorption, H₂-TPR, CO₂-TPD, TEM, XPS and TPO. The modification of the alumina support with alkaline earth oxides (MgO and CaO) and lanthanide oxides (La₂O₃), as promoters, is found to improve the dispersion of Ni, enhance the catalyst's basicity and metal-support interaction, as well as influence the nature of carbon deposition. The Ni catalyst supported on modified alumina with La₂O₃ exhibits a relatively stable syngas yield during 8 h of operation, while H₂ and CO yields decrease substantially for Ni/Al₂O₃.     

Hetero-structure CdS–CuFe2O4 as an efficient visible light active photocatalyst for photoelectrochemical reduction of CO2 to methanol

In the present paper, hetero-structured CdS–CuFe₂O₄ nanocomposite was synthesized by a facial method to convert CO₂ to methanol in the photoelectrochemical (PEC) system. The synthesized catalysts were characterised by XRD, Raman spectroscopy, TEM, FESEM, EDX, XPS, UV–vis and PL spectroscopy. The CdS–CuFe₂O₄ photocatalyst showed ~6 times higher photocurrent compared to the CuFe₂O₄ at −0.35 V vs. NHE of bias potential under CO₂ environment as revealed by chronoamperometry results. Incident photon to current efficiency (IPCE) for CuFe₂O₄ and CdS–CuFe₂O₄ at 470 nm were found as 7.28 and 12.09%, respectively which clearly indicates the proficiency of CdS–CuFe₂O₄ heterojunction to absorb the visible light resulting in e⁻/h⁺ generation and the charge transfer during PEC CO₂ reduction. Products in aqueous and gas phases were analysed which confirmed the selective production of methanol with trace amounts of H₂ and CO. The CdS–CuFe₂O₄ catalyst demonstrated 72% and 16.9% of Faradaic and quantum efficiencies, respectively in terms of methanol production where a methanol yield of 23.80 μmole/Lcm² was achieved in CO₂ saturated aqueous solution of NaHCO₃ (0.1 M). Detailed investigation revealed that the conduction band (CB) of the CdS in the heterojunction catalyst could act as a CO₂ reduction site by trapping photogenerated electrons from the highly photosensitive CuFe₂O₄ while the water oxidation could take place at the valance band (VB) of CuFe₂O₄.     

One-pot synthesis of Cu–TiO2/CuO nanocomposite: Application to photocatalysis for enhanced H2 production,dye degradation & detoxification of Cr (VI)

Photocatalytic hydrogen production under the visible spectrum of solar light is an important topic of research. To achieve the targeted visible light hydrogen production and improve the charge carrier utilization, bandgap engineering and surface modification of the photocatalyst plays a vital role. Present work reports the one-pot synthesis of Cu–TiO₂/CuO nanocomposite photocatalyst using green surfactant -aided -ultrasonication method. The materials characterization data reveals the TiO₂ particle size of 20–25 nm and the existence of copper in the lattice as well as in the surface of anatase TiO₂. This is expected to facilitate better optical and surface properties. The optimized photocatalyst shows enhanced H₂ production rate of 10,453 μmol h⁻¹ g⁻¹ of the catalyst which is 21 fold higher than pure TiO₂ nanoparticles. The photocatalyst was tested for degradation of methylene blue dye (90% in 4 h) in aqueous solution and photocatalytic reduction of toxic Cr⁶⁺ ions (55% in 4 h) in aqueous solution. A plausible mechanistic pathway is also proposed.     

Photocatalytic H2 production from glycerol–water mixtures over Ni/γ-Al2O3 and TiO2 composite systems

Ni/γ-Al₂O₃ prepared by impregnation, Ni/γ-Al₂O₃/CNT prepared in-situ during glycerol steam reforming, Ni/γ-Al₂O₃–TiO₂ and Ni/γ-Al₂O₃/CNT-TiO₂ were prepared by solid-state dispersion methods. These catalysts were characterized by XRD, SEM–EDAX, UV–Vis DRS, TEM, Raman and FT-IR techniques and were evaluated as photocatalysts for the production of H₂ using glycerol:water mixtures under solar light irradiation. For the first-time, higher rate of H₂ (3400 μmol h^?1 g^?1_cat) evolution was observed under the optimized conditions using Ni/γ-Al₂O₃/CNT-TiO₂ as a photocatalyst. This enhancement may be seen as due to the favorable absorption of solar light and the structural parameters minimizing the recombination of electron–hole pairs that resulted in improved activity of the catalyst. The present study clearly demonstrates that Ni/γ-Al₂O₃/CNT-TiO₂ as most promising photocatalyst for H₂ production from glycerol–water mixtures under solar light irradiation and through characterization, the structure–activity could be established.     

Promoted Ni–Co–Al2O3 nanostructured catalysts for CO2 methanation

15 wt.%Ni-12.5 wt.%Co–Al₂O₃ catalysts promoted with Fe, Mn, Cu, Zr, La, Ce, and Ba were prepared by a novel solid-state synthesis method and employed in CO₂ methanation reaction. BET, XRD, EDS, SEM, TPR, TGA, and FTIR analyses were conducted to identify the chemicophysical characteristics of the prepared samples. The addition of Fe, Mn, La, Ce, and Ba was effective to improve the catalytic performance of the 15 wt%Ni-12.5 wt%Co–Al₂O₃ due to the higher CO₂ adsorption capacity of the promoted catalysts. Among the studied promoters, the Fe-promoted catalyst possessed the highest catalytic activity (X_CO2 = 61.2% and S_CH4 = 98.87% at 300 °C). Also, the effect of calcination temperature, feed composition, and GHSV on the performance of the 15 wt%Ni-12.5 wt%Co-5wt%Fe–Al₂O₃ catalyst in CO₂ methanation reaction was assessed. The outcomes confirmed that the 15 wt%Ni-12.5 wt%Co-5wt%Fe–Al₂O₃ catalyst with the BET area of 122.4 m²/g and the highest pore volume and largest pore diameter had the highest catalytic activity. Also, the catalytic performance in the methanation of carbon monoxide was studied, and 100% conversion of carbon monoxide was observed at 250 °C.     

Optimization of CO2 reforming of methane process for the syngas production over Ni–Ce/TiO2–ZrO2 catalyst using the Taguchi method

In the present study, Taguchi method-based design of experiment with L9 orthogonal array was implemented to optimize the process conditions for CO₂ reforming of methane over the Ni–Ce/TiO₂–ZrO₂ catalyst. The catalyst composition, catalyst reduction temperature, reaction operating temperature, and the CO₂/CH₄ ratio of the reactant gas were the control parameters. The performance index was considered as the response of the Taguchi experiment. The performance index was calculated by considering the product gas H₂/CO ratio, deactivation factor, carbon deposition, and maximum CH₄ conversion. The catalysts were prepared in two steps using the evaporation-induced self-assembly and urea deposition-precipitation methods. The catalysts were characterized in their fresh and spent stages using various techniques like X-ray diffraction, N₂-physisorption, H₂ temperature-programmed reduction, inductively coupled plasma-mass spectroscopy, Scanning electron spectroscopy, Transmission electron spectroscopy, and Thermogravimetric analysis. The results showed that the operating temperature had the principal effect on the performance index. The optimal conditions from signal/noise ratio analysis were Cat3 catalyst with Ti/Zr ratio of 1:3, catalyst reduction temperature of 600 °C, the operating temperature of 800 °C, and feed gas ratio as CO₂/CH₄ = 2. Higher Zr content in the catalyst support and the lower reduction temperature favor enhancing the performance index.     

Phosphate-modified Al2O3–ZrO2 supported Ni catalysts for efficient selective methanation of CO in H2-rich reformate gas

CO selective methanation can remove the CO in H₂-rich reformate gas to prevent the poisoning of Pt anode electrode in proton exchange membrane fuel cell. However, the methanation of CO₂ in H₂-rich gas consumes a lot of hydrogen, which greatly reduces the energy efficiency. In order to inhibit CO₂ methanation, mesostructured Al₂O₃–ZrO₂ was modified by different amounts of phosphate, and then was as Ni support. The structures and surface properties of Ni/Al₂O₃–ZrO₂ catalyst modified by phosphate were studied to reveal the effect of phosphate-modification on CO conversion and selectivity for CO methanation. It was found that the phosphate-modification inhibited the adsorption of CO₂, which increased the selective for CO methanation. But the modification with excess phosphate lessened active sites of Ni and weakened the adsorption of H₂ and CO, which decreased the activity of CO methanation.