Structural and textural study of Ni and/or Co in a common molybdate lattice as catalysts

Boukhlouf, Hamza; Benrabaa, Rafik; Barama, Akila

doi:10.1051/matecconf/20130504023

Cited by 2 publications

(1 citation statement)

References 14 publications

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“…All the catalyst designations were based on data obtained from inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis (Table ). Boukholf et al made an interesting observation in his study that NiMoO 4 formation was favored when Ni is dominant on the surface, while Co 3 MoO 4 occurs on the Mo-rich surface . The line scans corroborate this with higher Mo and Ni concentrations on the surface for Ni 56 Co 7 Mo 37 and Ni 66 Co 31 Mo 3 , respectively (Figure c,d).…”

Section: Resultsmentioning

confidence: 59%

Tuning the Ni/Co Ratios and Surface Concentration of Reduced Molybdenum States for Enhanced Electrocatalytic Performance in Trimetallic Molybdates: OER, HER, and MOR Activity

Maarisetty

Hang

Chou

et al. 2022

ACS Appl. Energy Mater.

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The heterogeneous nature of trimetallic catalyst systems comes with beneficial synergy for catalytic applications. Nonetheless, the challenges associated to validate and control the critical characteristics for enhanced electrocatalytic efficiencies are yet to be known. Herein, a genre of trimetallic catalysts were synthesized with Ni, Co, and Mo metals, whose morphological, structural, electronic, and interface properties depend on Ni/Co and Mo+4/Mo+5 ratios and the dominant element on the surface of the catalyst. The results suggest that introduction of a third metal, that is, Mo, is only beneficial when the Ni/Co ratio is optimally maintained. By combining the surface electronic and structural analyses such as electron energy loss spectroscopy, X-ray photoelectron spectroscopy, line scan, Raman spectra, and electrochemical data, it was realized that Mo and metallic Ni on the surface favor oxygen evolution reaction (OER), and methanol oxidation reaction (MOR) activity, respectively. Interestingly, the adsorbed water molecules were found to be vital for higher performance in both OER and MOR processes. The chronopotentiometry tests performed with the optimized catalyst Ni56Co7Mo37 for OER showed an overpotential around ca. 309 mV at ca. 720 mA·cm–2 even after 17 h (and also a Tafel slope of 60 mV·dec–1 at 10 mA·cm–2). The peak current density (from the cyclic voltammetry tests) in the optimized catalyst, that is, Ni66Co31Mo3 (for MOR), showed almost 300-fold higher activity in 1 M KOH + 1 M CH3OH solution when compared with only 1 M KOH. Further, comparative studies were also conducted with bimetallic catalysts of Ni, Co, and Mo to understand the better combinations for promoting OER, hydrogen evolution reaction, and MOR efficiencies. This work highlights the importance of maintaining the elemental composition ratios at the bulk and surface that lead to an active environment for OER and MOR processes and thereby opening gateways for a rational design of trimetallic electrocatalysts.

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Section: Resultsmentioning

confidence: 59%

Tuning the Ni/Co Ratios and Surface Concentration of Reduced Molybdenum States for Enhanced Electrocatalytic Performance in Trimetallic Molybdates: OER, HER, and MOR Activity

Maarisetty

Hang

Chou

et al. 2022

ACS Appl. Energy Mater.

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Hot Corrosion Behavior of TWAS and HVOF NiCr-Based Coatings in Molten Salt

et al. 2023

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In order to extend the life of boilers by applying an anti-corrosion coating without the need to dismantle them, it is advisable to find coatings that can be applied using cheaper and portable techniques, such as Twin Wire Arc Spray technology (TWAS). In this study, we compare selected NiCr-based coatings and two uncoated steel substrates (steel 1.7715 and 1.4903). Two coatings, Cr3C2 - 25% NiCr and Hastelloy C-276 are deposited using High velocity oxygen-fuel technology (HVOF) and three coatings, NiCrTi, NiCrMo, and Inconel 625, are deposited using TWAS. In addition to the corrosion weight gain during 50 cycles of loading in an 18% Na2SO4 and 82% Fe2(SO4)3 salt environment at 690 °C evaluated using the gravimetric method, the microstructure and phase composition of the coatings were analyzed on the samples after the exposure in order to compare the properties and gain a deeper understanding of the corrosion kinetics. Coating cross-sections and free-surfaces were observed with a scanning electron microscope (SEM) with an energy-dispersive (EDX) system. The phase composition was investigated using X-ray diffraction (XRD) and Raman spectroscopy. No significant differences were observed between the TWAS and HVOF coating methods for the coatings compared. Due to the similar corrosion products found on all coatings, a very effective corrosion protective layer was formed on the surface, forming a barrier between the corrosive environment and the coating regardless of the used deposition technology. Therefore, for industrial use on the inner surface of coal-fired boilers we recommend NiCrTi, NiCrMo, or Inconel coatings prepared with the more cost-effective and portable TWAS technology.

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Structural and textural study of Ni and/or Co in a common molybdate lattice as catalysts

Cited by 2 publications

References 14 publications

Tuning the Ni/Co Ratios and Surface Concentration of Reduced Molybdenum States for Enhanced Electrocatalytic Performance in Trimetallic Molybdates: OER, HER, and MOR Activity

Tuning the Ni/Co Ratios and Surface Concentration of Reduced Molybdenum States for Enhanced Electrocatalytic Performance in Trimetallic Molybdates: OER, HER, and MOR Activity

Hot Corrosion Behavior of TWAS and HVOF NiCr-Based Coatings in Molten Salt

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