Search Results (93)

The urgent need to address the climate crisis demands a swift transition from fossil fuels to renewable energy. Clean hydrogen, produced through ethanol steam reforming (ESR), offers a viable solution. Traditional ESR operates at atmospheric pressure, requiring costly separation and compression of hydrogen. High-pressure ESR, however, improves hydrogen purification, streamlines processes like pressure swing adsorption, and reduces operational costs while enhancing energy efficiency. High-pressure ESR also enables compact reactor designs, minimizing equipment size and land use by compressing reactants into smaller volumes. This study evaluates two nickel-based commercial catalysts, AR-401 and NGPR-2, under high-pressure ESR conditions. Key parameters, including reaction temperature, steam-to-ethanol ratio, and weight hourly space velocity, were optimized. At 30 bars, 700 °C, and a steam-to-ethanol ratio of 9, both catalysts demonstrated complete ethanol conversion, with hydrogen selectivity of 65–70% and yields of 4–4.5 moles of H₂ per mole of ethanol. Raising the temperature to 850 °C improved hydrogen selectivity to 74% and yielded 5.2 moles of H₂ per mole. High-pressure ESR using renewable ethanol provides a scalable, efficient pathway for hydrogen production, supporting sustainable energy solutions. Full article

Hydrogen production by the electrolysis of water has become an important way to prepare green hydrogen because of its simple process and high product purity. However, the oxygen evolution reaction (OER) in the electrolysis process has a high overpotential, which leads to the increase of energy consumption. Developing efficient, stable and low-cost electrolytic water catalyst is the core challenge to reduce the reaction energy barrier and improve the energy conversion efficiency. CoS@NiS-80% nanosheets with rich heterogeneous interfaces were successfully synthesized by hydrothermal reaction and sulfuration. Heterogeneous interface not only promotes the effective charge transfer between different materials and reduces the charge transfer resistance but also accelerates the four-electron transfer process through the synergistic effect of nickel and cobalt atoms. Under alkaline conditions, the overpotential of CoS@NiS-80% nanosheets was only 280 mV at a current density of 10 mA cm⁻², with a Tafel slope of 100.87 mV dec⁻¹. Furthermore, it could work continuously for 100 h, exhibiting its outstanding stability. This work provides a novel approach for improving the OER performance of transition metal sulfide-based electrocatalysts through heterogeneous interface engineering. Full article

Ammonia is increasingly recognised as a promising carbon-free fuel and hydrogen carrier due to its high hydrogen content, ease of liquefaction, and existing global infrastructure. However, its direct utilisation in combustion systems poses significant challenges, including low flame speed, high ignition temperature, and the formation of nitrogen oxides (NO_X). This review explores catalytic ammonia cracking as a viable method to enhance combustion through in situ hydrogen production. It evaluates traditional catalytic burner designs originally developed for hydrocarbon fuels and assesses their adaptability for ammonia-based applications. Special attention is given to ruthenium- and nickel-based catalysts supported on various oxides and nanostructured materials, evaluating their ammonia conversion efficiency, resistance to sintering, and thermal stability. The impact of the main operational parameters, including reaction temperature and gas hourly space velocity (GHSV), is also discussed. Strategies for combining partial ammonia cracking with stable combustion are studied, with practical issues such as catalyst degradation, NO_X regulation, and system scalability. The analysis highlights recent advancements in structural catalyst support, which have potential for industrial-scale application. This review aims to provide future development of low-emission, high-efficiency catalytic burner systems and advance ammonia’s role in next-generation hydrogen energy technologies. Full article

The dry reforming of methane (DRM) converts two greenhouse gases, CH₄ and CO₂, into H₂ and CO, offering a crucial technological pathway for reducing greenhouse gas emissions and producing clean energy. However, the reaction faces two main challenges: high activation energy barriers require high temperatures to drive the reaction, while sintering and carbon deactivation at high temperatures are common with conventional nickel-based catalysts, which severely limit the further development of the methane dry reforming reaction. In this study, a nitrogen-doped carbon nanotube-loaded nickel catalytic system (Ni/NCNT) was developed to overcome the challenges caused by limited active sites while maintaining the stable structure of the Ni/CNT system. Ni/NCNT catalysts were prepared using different nitrogen precursors, and the impact of the mixing method on catalytic performance was examined. Characterization using H₂-TPR, XPS, and TEM revealed that nitrogen doping enhanced the metal–support interaction (MSI). Additionally, pyridine nitrogen species synergistically interact with nickel particles, modulating the electronic environment on the carbon nanotube surface and increasing catalyst active site density. The Ni/NCNT-IU catalyst, prepared with impregnated urea, exhibited excellent stability, with methane conversion decreasing from 85.0% to 82.9% over 24 h of continuous reaction. This study supports the use of non-precious-metal carbon-based catalysts in high-temperature catalytic systems, which is strategically important for the industrialization of DRM and the development of decarbonized energy conversion. Full article

Nickel (Ni) catalysts have numerous applications in the chemical industry, but they are susceptible to sulfurization, with their sulfurized structures and underlying formation mechanisms remaining unclear. Herein, density functional theory (DFT) combined with the particle swarm optimization (PSO) algorithm is employed to investigate the low-energy structures and formation mechanisms of sulfide phases on Ni(111) surfaces, especially under high-sulfur-coverage conditions where traditional DFT calculations fail to reach convergence. Using ($\sqrt{3}\times \sqrt{3}$ ) Ni(111) slab models, we identify a sulfurization limit, finding that each pair of deposited sulfur atoms can sulfurize one layer of three Ni atoms at most (Ni:S = 3:2), with additional sulfur atoms penetrating deeper layers until saturation. Under typical reactive adsorption desulfurization conditions, the ab initio thermodynamics analysis indicates that Ni₃S₂ is the most stable sulfide phase, consistent with sulfur K-edge XANES data. Unsaturated phases, including Ni₃S, Ni₂S, and Ni₉S₅, represent intermediate states towards saturation, potentially explaining the diverse Ni sulfide compositions observed in experiments. Full article

Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode. Full article

Recent endeavours to promote the widespread use of renewable and sustainable energy technologies depend heavily on the development and design of new catalytic materials. In this context, intermetallic compounds have come into the spotlight of recent research as a promising material class to tune the catalytic properties and stability for various uses. In this work, vapour–solid synthesis is highlighted as an outstanding method for its control over the composition and crystal structure of prepared intermetallic nanoparticles. Carbon black-supported nickel-telluride nanoparticles of different compositions and crystallographic structures have been synthesised and investigated regarding their oxygen reduction reaction performance in alkaline media. The relation between catalytic activity and ethanol tolerance depending on the various intermetallic phases has been investigated. The addition of tellurium into nickel-based nanoparticles allowed a two-fold increase of the mass activity from 43.6 A g_Ni⁻¹ for Ni/C to 88.5 A g_Ni⁻¹ for Ni-Te/C. Onset and half-wave potentials were comparable to commercial Pt/C benchmark catalyst. Furthermore, chronoamperometric testing showed that the ethanol-tolerant Ni-Te/C catalysts were stable under electrocatalytic conditions during in alkaline media. The trend in catalytic activity of the Ni-Te phases was followed the order: Ni₃Te₂ > NiTe > NiTe_2−x > Ni. Full article

This study explores the impact of scandium (Sc) as a promoter on the catalytic performance of 4Ni/MCM-41 catalysts for the partial oxidation of methane (POM). 4Ni+Sc/MCM-41 catalysts were synthesized with varying Sc loadings of 0, 0.2, 0.4, 0.6, and 0.8 wt.%. These catalysts were characterized using several techniques, including N₂ physisorption, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). All catalysts exhibited a mesoporous structure characterized by narrow slit-shaped pores. Among them, the 4Ni+0.2Sc/MCM-41 catalyst showed the most consistent pore size distribution. The addition of Sc (scandium) facilitated the formation of strongly interacting nickel species, which enhanced the initial catalytic activity. However, a trade-off was observed between initial activity and long-term stability. The optimal Sc loading was determined to be 0.2 wt.%. This catalyst achieved the highest methane conversion rate of 63.9%, a hydrogen yield of 60%, and an H₂/CO ratio of 2.7 while also demonstrating superior stability during extended operation. The 4Ni+0.2Sc/MCM-41 catalyst showed only a 7% weight loss in the thermogravimetric analysis (TGA), which shows that it will stay stable even after being used for a long time. The improved performance of the Sc-promoted catalysts is attributable to the increased availability of active sites, enhanced stability, and better dispersion of nickel. These efforts aim to create more sustainable and efficient methods for hydrogen production, minimizing the negative effects associated with traditional processes. By advancing these technologies, we can further support the transition to a cleaner energy future. Full article

The auto-thermal reforming (ATR) of acetic acid is an effective hydrogen production method, but it suffers from catalyst deactivation by coking. Sm-promoted layered La₂NiO₄ perovskite catalysts were synthesized via the sol–gel method and its catalytic performance in the ATR of HAc was further evaluated. The characterization results demonstrate that the incorporation of Sm into the lattice of La₂NiO₄ perovskite led to the formation of Ni-La-Sm-O species, inducing crystal defects in the perovskite structure which could promote the gasification of coking precursors. Additionally, Sm regulated the reduction characteristics of La₂NiO₄, resulting in the formation of highly dispersed nickel nanoparticles upon the hydrogen reduction, which increased the number of active sites available for acetic acid conversion. Consequently, a stable reactivity without obvious coking was obtained over a Ni_0.42La_0.7Sm_0.36O_2.01±δ catalyst within the ATR of Hac. The hydrogen yield reached 2.53 mol-H₂/mol-HAc along with the complete conversion of acetic acid. Full article

The construction of high-performance catalysts for overall water splitting (OWS) is crucial. Nickel–iron-layered double hydroxide (NiFe LDH) is a promising catalyst for OWS. However, the slow kinetics of the HER under alkaline conditions seriously hinder the application of NiFe LDH in OWS. This work presents a strategy to optimize OWS performance by adjusting the entropy of multi-metallic LDH. Quaternary NiFeCrCo LDH was constructed, which exhibited remarkable OWS activity. The OER and HER of NiFeCrCo LDH were stable for 100 h and 80 h, respectively. The OWS activity of NiFeCrCo LDH//NiFeCrCo LDH only required 1.42 V to reach 10 mA cm⁻², and 100 mA cm⁻² required 1.54 V. Under simulated seawater conditions, NiFeCrCo LDH//NiFeCrCo LDH required 1.57 V to reach 10 mA cm⁻² and 1.71 V to reach 100 mA cm⁻². The introduction of Co into the structure induced Cr to provide more electrons to Fe, which regulated the electronic state of NiFeCrCo LDH. The appropriate electronic state of the structure is essential for the remarkable performance of OWS. This work proposes a new strategy to achieve excellent OWS performance through entropy-increase engineering. Full article

The search for alternative sources of, and substitutes for, chemicals derived from fossil-based feedstocks encourages studies of heterogeneous catalysts to increase the feasibility of sustainable production of biomass derivatives, such as γ-valerolactone, among others. In this context, first, the performance of a titania-supported nickel catalyst (a non-noble catalyst) was evaluated in the reaction of hydrogenation of levulinic acid to γ-valerolactone in water using molecular hydrogen. The methods used included the synthesis of titania via the solgel method and nickel deposition by deposition–precipitation via removal of the complexing agent. The nickel was activated in a flow of hydrogen; the temperature of reduction and the calcination step were investigated with experiments at reaction conditions to study the catalyst’s stability. Then, after a statistical evaluation of several proposed kinetic models, the kinetics of the reaction was found to be best represented by a model obtained considering that the reaction over the surface was the determinant step, followed by the non-dissociative adsorption of hydrogen and the competitive adsorption among hydrogen, levulinic acid, and γ-valerolactone. With that model, the activation energy of the levulinic acid to 4-hydroxypentanoic acid step was (47.0 ± 1.2) kJ mol⁻¹, since the determinant step was the hydrogenation reaction of the levulinic acid to 4-hydroxypentanoic acid. It was also concluded that the catalyst prepared was stable, active, and selective to γ-valerolactone. Full article

The electrochemical carbon dioxide reduction reaction (CO₂RR) represents a promising approach for achieving CO₂ resource utilization. Carbon-based materials featuring single-atom transition metal-nitrogen coordination (M-N_x) have attracted considerable research attention due to their ability to maximize catalytic efficiency while minimizing metal atom usage. However, conventional synthesis methods often encounter challenges with metal particle agglomeration. In this study, we developed a Ni-doped polyvinylidene fluoride (PVDF) fiber membrane via electrospinning, subsequently transformed into a nitrogen-doped three-dimensional self-supporting single-atom Ni catalyst (Ni-N-CF) through controlled carbonization. PVDF was partially defluorinated and crosslinked, and the single carbon chain is changed into a reticulated structure, which ensured that the structure did not collapse during carbonization and effectively solved the problem of runaway M-Nx composite in the high-temperature pyrolysis process. Grounded in X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS), nitrogen coordinates with nickel atoms to form a Ni-N structure, which keeps nickel in a low oxidation state, thereby facilitating CO₂RR. When applied to CO₂RR, the Ni-N-CF catalyst demonstrated exceptional CO selectivity with a Faradaic efficiency (FE) of 92%. The unique self-supporting architecture effectively addressed traditional electrode instability issues caused by catalyst detachment. These results indicate that by tuning the local coordination structure of atomically dispersed Ni, the original inert reaction sites can be activated into efficient catalytic centers. This work can provide a new strategy for designing high-performance single-atom catalysts and structurally stable electrodes. Full article

Designing efficient and cost-effective electrocatalysts is crucial for the large-scale development of sustainable hydrogen energy. Amorphous catalysts hold great promise for application due to their structural flexibility and high exposure of active sites. We report a novel method for the in situ growth of amorphous CoNiRuO_x nanoparticle structures (CoNiRuO_x/NF) on a nickel foam substrate. In 1 m KOH, CoNiRuO_x/NF achieves a current density of 10 mA/cm² with a hydrogen evolution reaction (HER) overpotential of only 43 mV and remains stable for over 100 h at a current density of 100 mA/cm². An alkaline electrolyzer assembled with CoNiRuO_x/NF as the cathode delivers a current density 2.97 times higher than that of an IrO₂||Pt/C electrode pair at the potential of 2 V and exhibits excellent long-term durability exceeding 100 h. Experimental results reveal that the combined replacement and corrosion reactions facilitate the formation of the amorphous CoNiRuO_x structure. This work provides valuable insights for developing efficient and scalable amorphous catalysts. Full article

The utilization of red mud as a catalyst support has been investigated to produce high-value carbon and CO_x-free hydrogen from natural gas. Nickel impregnation between 10 wt% to 20 wt% over red mud generates more active species in the form of nickel oxide; however, nickel–red mud interaction also generates less active spinel species (NiFe₂O₄). The red mud itself deactivates quickly during the production of hydrogen from the decomposition of methane; however, nickel-based red mud-supported catalysts have shown significant improvement in the activity results. For instance, the catalyst with 20 wt% nickel supported by red mud demonstrates a stable methane conversion as high as 75%. The reduction kinetics analysis demonstrated the lowest reduction in activation energy of 83 kJ/mol for 20Ni-PRM which played a major role in the excellent activity and stability of this catalyst. The post-reaction catalyst characterization results indicate the formation of multi-walled carbon nanotubes, as evidenced by high resolution transition electron microscope and thermogravimetric analyses. Full article

Perovskites exhibit catalytic properties on the oxygen evolution reaction (OER) in water electrolysis. Elemental doping by specific preparation methods is a good strategy to obtain highly catalytical active perovskite catalysts. In this work, La_0.5Sr_0.5Co_1−xNi_xO_3−δ perovskite materials doped with different ratios of nickel were successfully synthesized by the sol-gel method. The electrochemical measurement results show that for OER in 1 M KOH solution, La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ prepared by the sol-gel method requires only a low overpotential of 213 mV to reach 10 mA cm⁻², which is significantly lower than that of La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ prepared by the hydrothermal method for the increasing about 45.24% (389 mV at 10 mA cm⁻²). In addition, La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ by the sol-gel method can be kept stable in an alkaline medium tested for 30 h without degradation. This indicates that the prepared La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ has better OER performance. The X-ray diffraction (XRD) results show that SrCO₃ is the main phase formed, which is a disadvantage of this method. The performance improvement may be affected by the carbonate phase. The scanning electron microscopy (SEM) results show that layer structured La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ by the sol-gel method has more surface pores with a pore diameter of about 0.362 μm than spherical granular structured La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ by the hydrothermal method. X-ray photoelectronic spectroscopy (XPS) results reveal that the crystal lattice of La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ by nickel doping is lengthened, and the electronic configuration of Co is also changed by the sol-gel preparation process. The improved electrocatalytic performance of La_0.5Sr_0.5Co_0.8Ni_0.2O_3−δ may be attributed to the pore structure formed providing more active sites during the sol-gel process and the improved oxygen mobility with Ni doping by the sol-gel method. The doping strategy using the sol-gel method provides valuable insights for optimizing perovskite catalytic properties. Full article