2O3 Catalyst Research Articles

Thermocatalytic decomposition of methane to low-carbon hydrogen using LaNi1-xCuxO3 perovskite catalysts

The thermocatalytic decomposition (TCD) of methane is an attractive alternative to produce low-carbon hydrogen and solid carbonaceous materials. In this study, substituted LaNi1-xCuxO3 perovskite catalysts prepared via self-combustion method were investigated for methane TCD. The effect of Ni partial substitution with Cu, varying gas hourly space velocity, temperature and stability on methane conversions were evaluated. PXRD, H2-TPR, SEM-EDS, TGA, and XPS were used to characterize the catalysts. An increase in Cu loading to 50%, increase in temperature and decrease in GHSV resulted in an improvement in methane conversions to 92%. At a GHSV of 2400 ml/gcat.h, no significant deactivation was observed as the stability of the LaNi0.5Cu0.5O3 catalyst increased from 6 to 20 hours’ TOS with methane conversions maintained at 92% where carbon nanofibers were observed on the surface of the spent catalysts. The study demonstrates the potential to prepare LaNi1-xCuxO3 catalysts and identify optimal testing conditions for the novel production of low-carbon hydrogen with minimal catalyst deactivation.

Nickel-containing catalysts for ethylene conversion to motor fuel components and light alkenes

Polyfunctional Ni-containing catalysts supported on the B2O3-Al2O3 and MoO3-Al2O3 were prepared by a sequential impregnation. They were evaluated in ethylene conversion to C5+ alkenes or propylene. The catalysts were characterized by X-ray diffraction, Fourier transformed infrared spectroscopy, Fourier transformed infrared spectroscopy of adsorbed CO, UV-VIS diffuse reflectance spectroscopy, temperature programmed reduction and temperature-programmed desorption of NH3. NiO/B2O3-Al2O3 samples containing Ni2+ cations chemically bonded to the acid support are the most effective catalysts for ethylene oligomerization. The NiO/MoO3-Al2O3 catalyst activity in the ethylene conversion to propylene is related with the presence of ethylene dimerization active sites, i.e. Ni2+ cations bonded to the support acidic sites, and active sites of metathesis in the form of monomolybdate species.

Understanding the catalytic performance and deactivation behaviour of second-promoter doped Pt/WOx/γ-Al2O3 catalysts in the glycerol hydrogenolysis for selective and cleaner production of 1,3-propanediol

The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol (1,3-PDO). The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenolysis but the catalyst deactivation via sintering, metal leaching, and coking can predominantly occur in the aqueous phase reaction. In this work, the effect of reaction temperature, pressure and second promoter (Cu, Fe, Rh, Mn, Re, Ru, Ir, Sn, B, and P) on catalytic performance and deactivation behaviour of Pt/WOx/γ-Al2O3 was investigated. When doped with Rh, Mn, Re, Ru, Ir, B, and P, the second promoter boosts catalytic activity by promoting great dispersion of Pt on support and increasing Pt surface area. The increased Brønsted acid sites lead to selective synthesis of 1,3-PDO than 1,2-propanediol (1,2-PDO). The characterization studies of fresh and spent catalysts reveal that the main cause of catalyst deactivation is the Pt sintering, as interpreted based on XRD, CO chemisorption, and TEM analyses. The Pt sintering is affected depending on the second promoter that can either or reduce the interaction between Pt, WOx, and Al2O3. As an electron acceptor of Pt in Pt/WOx/γ-Al2O3, Re and Mn as second promoters resulted in increased Pt2+ on the catalytic surface, which strengthens the contact between Pt and γ-Al2O3 and WOx, resulting in a decrease in Pt sintering. The metal leaching and coking are not affected by the presence of second promoter. The catalyst modified with a second promoter possesses improved catalytic activity and 1,3-PDO production, however the stability continues to remain a challenge. The present work unravelled the determining parameters of catalytic activity and deactivation, thus providing a promising protocol toward effective catalysts for glycerol hydrogenolysis.

Ex situ and in situ studies on structural features of Pt/Ce0.75Zr0.25O2 catalyst for water gas shift reaction

Pt/Ce1-xZrxO2 catalysts have shown high activity in water gas shift (WGS) reaction, but their structural organization has been studied insufficiently. This work represents a detailed structural study on the supported Pt species and the metal/support interface in a 5 wt% Pt/Ce0.75Zr0.25O2 catalyst in the initial state, after reductive activation, and after WGS reaction in H2-enriched reformate-simulating mixture. A wide range of methods was used: ex situ and in situ X-ray diffraction (XRD) studies, high resolution transmission electron microscopy (HRTEM), X-ray atomic pair distribution function (PDF) method, pseudo in situ X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR). The Ce0.75Zr0.25O2 mixed oxide was shown to provide a highly dispersed state of Pt species. XPS revealed that the initial catalyst contains Pt2+species. PDF analysis allowed us to propose the structure of ultrafine PtO particles and to elucidate the metal-support interaction with fixation of Pt ions on the support surface. In situ XRD, pseudo in situ XPS, and H2-TPR studies revealed the reduction of ultrafine PtO particles in H2 atmosphere at low temperatures (20–90°С) with the formation of metallic Pt0 particles and simultaneous partial reduction of the support surface due to the hydrogen spillover. Catalytic tests of the as-prepared and poisoned with chlorine 5wt% Pt/Ce0.75Zr0.25O2 catalysts in the WGS reaction showed an important role of the oxygen vacancies in the oxide support as active sites. These findings contribute to the understanding catalytic performance of Pt/Ce1-xZrxO2 systems.

Role of oxophilic metal ions (Mo, Zr, Ti) impregnated Ni/γ-Al2O3 catalysts for hydrothermal liquefaction of kraft lignin

In this study, the effect of oxophilic metal ions (Mo, Zr, and Ti) loaded Ni/γ-Al2O3 (Al) catalysts was explored for the first time for the hydrothermal liquefaction of kraft lignin using IPA for 30 min/280 °C. The liquefaction of lignin was noticed to be 65.4 wt% with 10 wt% loaded Ni/Al with an 81.3% total conversion. The performance of Ni/Al was enhanced remarkably by using the oxophilic metal ions as promoters owing to an increase in the Lewis character of the catalyst's surface. The bio-oil yield was a maximum of 72 wt% with a 91.5% conversion using 3 wt% loaded Ti–10Ni/Al. The different alcoholic solvents such as methanol, ethanol, and IPA were also examined for the same. However, the best liquefaction was noticed with IPA owing to better H-donor tendency. Additionally, a series of IPA-water co-solvent examinations attributed to a significant improvement in the liquefaction to 74.8 wt% (50:50) IPA-water system. The optimum catalyst 10Ni–3Ti/Al was tested for four catalytic cycles, which indicated a slight loss in the catalytic activity because of blockage of the catalytic active site by char deposition. The GC-MS investigation of optimum catalytic bio-oil showed the highest selectivity of acetosyringone (68.5%) and 2-methoxy-phenol (22.8%), which was observed to be only 30.1 and 5.1% for non-catalytic bio-oil. The 1H NMR and FT-IR investigation of raw lignin and bio-oil proved the breakage of lignin's 3D structure into respective G-and S-type monomeric compounds. Additionally, catalysts were characterized using the XRD, BET, and XPS analysis.

A stable flow hydrogen production of sodium borohydride hydrolysis using millimeter-scale Ru/Al2O3 spheres as catalyst

In this study, we investigated the performance of continuous flow hydrogen production from NaBH4 hydrolysis by loading Ru onto millimeter-scale Al2O3 spheres (0.5–1 mm in diameter) (Ru/m-Al2O3) using a simple impregnation method. The results from transmission electron microscopy (TEM) and N2 adsorption and desorption revealed that Ru particles, with an average size of 2.73 nm, were evenly distributed on the Al2O3 spheres, and the catalysts exhibited a typical mesoporous structure. The study investigated the impact of Ru loading, catalyst quantity, catalyst reduction temperature, hydrogen production temperature, feeding rate, and concentrations of NaBH4 and NaOH on the rate of hydrogen production (HPR). The evaluation of hydrogen production revealed that the top-performing Ru/m-Al2O3 catalyst achieved a HPR of 22.44 L min–1 gRu–1 at 30 °C, with an apparent activation energy (Ea) of 33.98 kJ mol–1. The catalyst could continuously produce hydrogen for 1700 min with a 20 % decrease in activity. The characterization results before and after hydrogen production revealed that Ru/m-Al2O3 exhibited excellent structural stability after a prolonged period of hydrogen production, with no apparent changes in its morphology, crystal structure, Ru particle size, and pore structure. In addition, the X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and hydrogen production performance results showed that the flow system could effectively prevent the aggregation of NaBO2 on the catalyst's surface, thereby significantly improving the hydrogen production activity.

Enhanced Ru-O-Ce interaction by solid solution structure of Ru-CexZr1-xO2 catalysts for efficient catalytic combustion of vinyl chloride

Ru-CexZr1-xO2 catalysts, prepared by stepwise precipitation method, were investigated for the catalytic combustion of vinyl chloride (VC). Ru-O-Ce is a highly reactive structure in the redox ability. The Ce-O-Zr solid solution structure enhances the strong metal-support-interaction (SMSI) between Ru and Ce, thereby increasing the content of Ru-O-Ce structure, which can be modulated by the molar ratio of Ce/(Ce + Zr) in the catalyst. Zr doping also enhances the surface acid sites. In situ DRIFTS reveals that Ru-CexZr1-xO2 catalyst avoids chlorine poisoning, and Ru-O-Ce provides sufficient chemically adsorbed oxygen species (CAOS) to promote formation of formate intermediate species. Ru-Ce0.5Zr0.5O2 catalyst exhibited the best catalytic performance with T90 of 227 °C under the reaction conditions of 1000 ppm VC and WHSV of 30,000 mL·g−1·h−1. Moreover, Ru-Ce0.5Zr0.5O2 catalyst exhibited the superior resistance to high temperature, chlorine poisoning and water, and excellent catalytic activity for the catalytic combustion of various VOCs.

N-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors to prepare CoMoS/Al2O3 catalysts for highly selective hydrodesulfurization of thiophene

A novel (C11H26N)2Co(MoS4)2 complex was prepared via the n-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors for the selective hydrodesulfurization (HDS) of thiophene. The complex was generated by the interaction between the negatively charged CoMo compound and the positively charged n-octyltrimethylammonium ions. Then positively charged bimolecular layers were formed owing to van der Waals forces between the C11H26N+ and the complex, and they were anchored on the negatively charged γ-Al2O3. Compared with CoMoS/γ-Al2O3 catalysts prepared by impregnation, the optimal CoMoN-0.3/γ-Al2O3 catalyst exhibited better performance for selective HDS due to the enhanced Mo dispersion, the close contact between Co and Mo, and the increased amount of CoMoS phases on γ-Al2O3. Among these catalysts, the optimal CoMoN-0.3/γ-Al2O3 catalyst with the highest concentration of CoMoS phases exhibited the highest HDS reaction rate constant of 6.95 × 10-6 mol·g−1·s−1 and the best selective factor of 26.1 for the selective HDS of thiophene with 1-hexene.

Unveiling the synergistic effects of pH and Sn content for tuning the catalytic performance of Ni0/NixSny intermetallic compounds dispersed on Ce-Zr mixed oxides in the aqueous phase reforming of ethylene glycol

The product distribution in aqueous phase reforming (APR) of polyols is closely tied to the catalytically induced feed cleavage mechanism. Strategic variations in catalyst composition and synergistic effects prompted by reaction conditions, such as pH, can be utilized to tune the product distribution of both liquid and gaseous phases. This study aimed to compare the physicochemical properties of various NixSny/Ce(Zr)O2 catalysts and their performance in batch tests during the APR of a 6%wt. ethylene glycol (EG) solution under both neutral and alkaline conditions. The results show that the progressive addition of tin strongly tunes the activity of the catalysts and the nickel-induced methanation reaction under neutral conditions, albeit decreasing feed conversions. In synergy with tin tuning, the alkaline environment boosts the process by increasing conversions and H2-yields while still minimizing methanation due to the alkali-induced process of Cannizzaro disproportionation of EG into glycolic acid with subsequent reforming thereof.

Syngas production from dry reforming of glycerol by the NiO/M-Al2O3 catalysts: Effect of various support promoters and various ZrO2 content

Glycerol dry reforming presents an intriguing approach for converting CO2, a greenhouse gas, and glycerol, a renewable resource, into syngas. This study delves into the impact of introducing 5 wt% of ZrO2, CeO2, La2O3, and Y2O3 to the Al2O3 support. Additionally, the study examines the influence of the optimal metal oxide ratio within the support formula on both structural properties and catalytic performance in the glycerol dry reforming process. To investigate these aspects, various catalyst supports were synthesized using a mechanochemical method. Subsequently, nickel-based catalysts were prepared through a wet impregnation technique. The catalysts underwent comprehensive characterization employing techniques such as XRD, BET, H2-TPR, CO2-TPD, TPO, and FESEM analyses to determine their physicochemical properties. The results demonstrated that the sample enhanced with 5 wt% ZrO2 exhibited remarkable performance metrics. Notably, it achieved a catalytic activity of 85.4% glycerol conversion at 650 ℃, while also displaying better stability and resistance to carbon deposition compared to the unpromoted catalyst throughout a 600 minutes reaction period. These enhanced attributes were attributed to the heightened specific surface area of the support (241.95 m2/gr), the effective dispersion of Ni on the support and the increase in basic sites.

Hematite-Gamma Alumina-based Solid Catalyst Development for Biodiesel Production from Palm Oil

This research investigated the performance of hematite-gamma alumina (Fe2O3/γ-Al2O3) catalyst in biodiesel production from palm oil. A full factorial experimental design was utilized to analyze the effect of hematite content, catalyst loading, and methanol-to-oil ratio on catalyst performance. From the experiment, biodiesel in the range of 73.6 to 87.6% FAME content was obtained. It was concluded that the catalyst composition, the methanol-to-oil ratio, and the catalyst loading have a significant effect on the FAME content of the biodiesel. Hematite has strong affinity for fatty acids, so a larger hematite surface area will result in a higher fatty acid absorption capacity. The addition of excess methanol can reduce the contact inhibition between the reactants and the active site of the catalyst, thereby increasing the conversion rate of the reaction. Moreover, a higher amount of catalyst loading can result in an increase in the FAME content when accompanied by an increase in the hematite content of the catalyst.

Crystal Plane Regulation Promotes the Oriented Conversion of Radicals in Heterogeneous Persulfate Catalyzed Oxidation Process.

In heterogeneous persulfate-catalyzed oxidation systems, the mechanism underlying the crystal plane effects of the catalyst on the selective conversion of reactive oxygen species (ROS) remains ambiguous. In this study, nano-Co3O4 catalysts with varying crystallinity and exposure levels of (111) crystal planes are prepared via a hydrothermal method. Compared to low crystalline catalysts, high crystallinity catalysts predominantly expose (111) planes containing higher concentrations of Co2+ and oxygen vacancies (Ov), resulting in an increase degradation efficiency of p-nitrobenzaldehyde (4-NBA) from 74.5% to 100%. Radical quenching experiments and EPR characterization reveal that the degradation of 4-NBA occurs through a radical pathway, and quantification of radicals demonstrates that increasing exposure levels of (111) planes effectively promote radical yield (CSO4•- increase from 18.2 to 172.8 µm and C•OH increase from 1 to 58.9 µm). Furthermore, XPS and DFT calculations indicate that high crystallinity catalyst possesses more Ov active sites on (111) planes. The presence of Ov not only facilitates the adsorption of PMS molecules but also enhances electron transfer from Co2+ to PMS, leading to directed formation and efficient transformation of radicals. This study presents a novel strategy for promoting efficient radical formation in persulfate-activated systems.

Advanced treatment of landfill leachate by catalytic ozonation with MnCeOx/γ-Al2O3 catalyst

Ozonation combined with an efficient and stable catalyst has been demonstrated to be a feasible solution in for removing refractory contaminants from landfill leachate. In this study, MnCeOx/γ-Al2O3 catalyst fabricated with impregnation method was adopted as ozone catalyst for advanced treatment of landfill leachate biochemical effluent (LLBE). The optimized Mn80Ce20Ox/γ-Al2O3 catalyst was fabricated with Mn/Ce molar ratio of 4:1, a metal oxide loading amount of 3.1 wt%, and calcination temperature of 500 °C. By treating LLBE, the removal of chemical oxygen demand (COD) and UV254 in 120 min reached 82.4 % and 96.3 %, respectively, with ozone dose of 15.3 mg L−1, catalyst dosage of 250 g L−1, and the initial pH of 5. The Mn80Ce20Ox/γ-Al2O3 catalyzed ozonation process conformed to pseudo-first-order kinetics with degradation rate constants of 0.0171 min−1 and 0.0313 min−1 for COD and UV254, respectively, which were 3.4 and 2.8 times higher than those of ozonation alone. The MnCeOx/γ-Al2O3 also showed satisfactory catalytic activity and stability based on eight times catalytic ozonation treatments on LLBE.

The reduction of copper in LaFeO3, La2CuO4 and CuO three-phase system improves the efficiency of NO removal: Experimental and density functional theory calculation

Hollow spherical LaCu0.5Fe0.5O3 (LCF) and La0.8Ce0.1Cu0.5Fe0.5O3 (LCCF) catalysts are synthesized by solvothermal method, and CuO is reduced in two samples, so that the two corresponding multiphase catalysts (R-LCF and R-LCCF) were prepared and used for the selective catalytic reduction of NO with CO (CO-SCR). The results show that the balance of Ce3++Cu2+↔Cu++Ce4+ between Ce and Cu ions promotes the reduction of CuO in the Ce-doped LCCF catalyst more obviously. In addition, the reduction of Ce and Cu in R-LCCF generates more oxygen vacancies, which leads to more surface adsorbed oxygen species, thus facilitating the conversion of more NO to NOx species. Besides, the presence of reduced Cu is highly active and can inhibit the production of carbonates occupying the active site. The ability to activate both CO and NO after the evolution of Cu0 to the key species Cu+ leads to a rapid reaction between Cu+-CO and NOx species. These are the key factors for the significant increase in catalytic activity at low temperatures. It is worth noting that the CO-SCR reaction on the R-LCCF catalyst corresponds to the Langmuir-Hinshlwood (L-H) and Eley-Rideal (E-R) mechanisms at different temperature windows, respectively.

Mechanistic and kinetics insights into Cu size effects on catalytic hydrogen combustion

The removal of excess hydrogen in a catalytic process is a safety measure, which should be incorporated into fuel cell technologies. In this study, the size effects of Cu catalysts on the catalytic hydrogen combustion are examined by investigating the impact of Cu–Cu and Cu–O coordination numbers. A distinct volcano-shaped trend in catalytic performance is observed, reaching its peak when the Cu loading is at 5 wt% with a reaction rate of 0.55 molH2·molCu−1·min−1. It is found that the lower Cu loading leads to strong metal-support interactions and a high Cu–O coordination, whereas the higher Cu loading hinders reduction and increases the Cu–Cu coordination. DFT calculations emphasize the significance of Cu(111) facets in facilitating HH bond dissociation and OH bond formation. However, excessively large Cu nanoparticles limit catalytic activity due to the reduced active sites. As a result, the 5 wt% Cu/γ-Al2O3 catalyst, which strikes a balance between Cu–Cu and Cu–O coordination numbers, exhibits the highest catalytic performance for this reaction. This study not only provides valuable insights into the size effects of Cu–based catalysts on hydrogen combustion, but also offers guidance for designing highly active Cu–based catalysts.

Catalytic conversion of chicken fats into fuel grade hydrocarbons

Fatty acid is considered as a renewable source for producing transportation fuel. As there is an ongoing price hike of diesel and kerosene as well as a lack of sustainable fuel to mitigate global climate change, the current study developed a one-step process of fuel grade hydrocarbons production from low-grade chicken fats (as a fatty acid source) using NiO/γ-Al2O3 catalysts. Results showed that straight-chain hydrocarbons were obtained through deoxygenation of chicken fats at different temperatures (350 to 400 °C) and reaction times (0.25 to 1 h). 65% liquid yield and 87% degree of deoxygenation were obtained at the optimum reaction conditions (400 °C and 1 h) using 5 wt%NiO/γ-Al2O3 catalyst, whereas the liquid product contains 18.7% C8 to C15 alkanes, 38.5% hexadecane, 39% heptadecane and 3.8% C18 to C20 alkanes. Liquid product has a similar high heating value (HHV) and density as a commercial fuel such as diesel. This work opens a new research window in the field of green energy to improve global energy security.

Synergistic effects of surface acidity and alkalinity of Ni/γ-Al2O3 catalysts in fats and oils hydrodeoxygenation product distribution

The deep utilization of green and renewable chemicals has laid the foundation for sustainable development. Recombining and modifying the long carbon chain structure and oxygen-containing functional groups in fats and oils can prepare important chemical products, such as high-quality second-generation biodiesel and oxygen-containing compounds (fatty alcohols, fatty acids, and esters). To improve the hydrodeoxygenation (HDO) performances of Ni-based catalysts, the effect of surface composition was studied in detail. Acid-base centers of Ni/γ-Al2O3 catalysts were finely regulated by adding metal oxides (ZrO2, CeO2, La2O3, and MgO). It was found that enhancing the basicity of the studied catalyst was conducive to the methyl laurate conversion, but was not conducive to the HDO of oxygen-containing intermediates. In other words, the strong basicity would promote the condensation reaction of oxygen-containing intermediates over Ni-based catalyst. Among the studied catalysts, Ni/La2O3/γ-Al2O3 catalyst showed the highest methyl laurate conversion (73%) and oxygen-containing product selectivity (64%) at 400 °C, LHSV = 1.5 h−1, H2/oil = 500 Nm3/m3, and PH2 = 2.0 MPa over the Ni/La2O3/γ-Al2O3 catalyst. The acidity was favorable to improve the conversion of oils and the yield of alkane products, and the basicity was favorable to obtain oxygen-containing compounds over the corresponding catalysts.

Vapor-phase deoxydehydration of 1,2-propanediol to form propylene over Cu-loaded H3PO4/SiO2-Al2O3 catalyst

Vapor-phase catalytic deoxydehydration of 1,2-propanediol (1,2-PDO) to form propylene was performed over various metal-loaded catalysts in an H2 flow at an ambient pressure. Cu-based catalysts exhibited a relatively high activity for the formation of propylene, while other metal-based catalysts, such as Pt-, Ru-, Rh-, Ni-, and Co-loaded SiO2-Al2O3, primarily produced C-C bond cleavage products. Cu-loaded H3PO4/SiO2-Al2O3 catalysts showed the best catalytic performance, and the catalyst with a Cu and H3PO4 loading of 8 and 10 wt%, respectively, could provide a propylene selectivity of 95.0% with a complete conversion of 1,2-PDO at 280 °C. The Cu-loaded H3PO4/SiO2-Al2O3 catalysts primarily contained Lewis acid sites, and the Cu particles were well dispersed on the catalyst surface with an averaged particle size of 3.1 nm. It is proposed that the vapor-phase deoxydehydration of 1,2-PDO to propylene undergoes multi-step reactions with propanal and 1-propanol as the reaction intermediates.

Preparation of chromium barium oxide catalysts for hydrogen evolution from sodium borohydride methanolysis

This paper describes the synthesis of Cr2O3, Cr1.7Ba0.3O3, and Cr1.4Ba0.6O3 nanoparticles as catalysts to enhance hydrogen evolution in sodium borohydride methanolysis. Various characterization techniques, comprising X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and others were utilized to characterize the prepared nanoparticles. The XRD analysis showed that the formed Cr2O3 exhibits a hexagonal crystal structure, with an estimated mean crystallite size of 24 nm. SEM micrographs showed nanoparticles with homogeneous distributions, exhibiting spherical or distorted spherical shapes. XPS analysis showed that all synthetic Cr2-xBaxO3 materials consist of Cr, O, and the presence of Ba for doped samples. The energy gap for pure Cr2O3 nanoparticles was determined to be 3.28 eV. Inclusion of Ba into the Cr2O3 nanostructure modified the band gap, resulting in values of 2.8 and 1.5 eV at 15 % and 30 % barium content. The hydrogen production rate from NaBH4 methanolysis for Cr2O3, Cr1.7Ba0.3O3, and Cr1.4Ba0.6O3 catalysts were 5984, 31176 and 11913 mL/g.min, respectively.

A High-Performance Cr2O3/CaCO3 Nanocomposite Catalyst for Rapid Hydrogen Generation from NaBH4.

This study aims to prepare new nanocomposites consisting of Cr2O3/CaCO3 as a catalyst for improved hydrogen production from NaBH4 methanolysis. The new nanocomposite possesses nanoparticles with the compositional formula Cr2-xCaxO3 (x = 0, 0.3, and 0.6). These samples were prepared using the sol-gel method, which comprises gelatin fuel. The structure of the new composites was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, environmental scanning electron microscopy (ESEM), and X-ray spectroscopy (XPS). The XRD data showed the rhombohedral crystallinity of the studied samples, and the average crystal size was 25 nm. The FTIR measurements represented the absorption bands of Cr2O3 and CaO. The ESEM micrographs of the Cr2O3 showed the spherical shape of the Cr2O3 nanoparticles. The XPS measurements proved the desired oxidation states of the Cr2-xCaxO3 nanoparticles. The optical band gap of Cr2O3 is 3.0 eV, and calcium doping causes a reduction to 2.5 and 1.3 eV at 15.0 and 30.0% doping ratios. The methanolysis of NaBH4 involved accelerated H2 production when using Cr2-xCaxO3 as a catalyst. Furthermore, the Cr1.7Ca0.3O3 catalyst had the highest hydrogen generation rate, with a value of 12,750 mL/g/min.