NiSe2/CeO2 catalysts from Ce-UiO-66 metal-organic skeletons and their electrocatalytic oxidation of methanol, urea and glycerol.

Hydrogen is a viable alternative energy source to fossil fuels. In order to manufacture enough hydrogen to meet the needs of social growth, finding an alternate energy source that is more effective is essential. Electrochemical water cracking is a more appropriate method for producing hydrogen. The methanol oxidation reaction (MOR), urea oxidation reaction (UOR) and glycerol oxidation reaction (GOR) can be used to replace the anodic oxygen evolution reaction (OER) and indirectly accelerate the hydrogen evolution reaction (HER), which has the advantages of saving energy and reducing environmental pollution. In this study, Ni/CeO2 catalysts were prepared by thermal annealing of MOFs (Ce-UiO-66) containing nickel species and NiSe2/CeO2 nanocrystalline catalysts were obtained through the selenation reaction at different temperatures. The NiSe2/CeO2-450 °C catalysts exhibited superior catalytic performance for the MOR, UOR, and GOR. The MOR showed a peak current density of roughly 186.68 mA cm-2 and a low oxidation potential of around 1.34 V. Similarly, the UOR demonstrated a peak current density of approximately 142.28 mA cm-2 and a low oxidation potential of around 1.32 V. Furthermore, the GOR exhibited a peak current density of approximately 82.56 mA cm-2 and a low oxidation potential of around 1.37 V. NiSe2/CeO2-450 °C could improve electrocatalytic performance for the MOR, UOR, and GOR, which is attributed to the more active sites that were exposed as a result of utilizing MOFs (Ce-UiO-66) as a precursor. Additionally, selenation increased the ability to transfer electrons. This research is crucial for the production of inexpensive, easily accessible transition metals in place of expensive noble metals, for the reduction of wastewater pollution from methanol and urea, and for the creation of effective anodic oxidation electrocatalysts.

Preparation of 3D Nd2O3-NiSe-Modified Nitrogen-Doped Carbon and Its Electrocatalytic Oxidation of Methanol and Urea.

Developing renewable energy sources and controlling water pollution are critical but challenging problems. Urea oxidation (UOR) and methanol oxidation (MOR), both of which have high research value, have the potential to effectively address wastewater pollution and energy crisis problems. A three-dimensional neodymium-dioxide/nickel-selenide-modified nitrogen-doped carbon nanosheet (Nd2O3-NiSe-NC) catalyst is prepared in this study by using mixed freeze-drying, salt-template-assisted technology, and high-temperature pyrolysis. The Nd2O3-NiSe-NC electrode showed good catalytic activity for MOR (peak current density ~145.04 mA cm-2 and low oxidation potential ~1.33 V) and UOR (peak current density ~100.68 mA cm-2 and low oxidation potential ~1.32 V); the catalyst has excellent MOR and UOR characteristics. The electrochemical reaction activity and the electron transfer rate increased because of selenide and carbon doping. Moreover, the synergistic action of neodymium oxide doping, nickel selenide, and the oxygen vacancy generated at the interface can adjust the electronic structure. The doping of rare-earth-metal oxides can also effectively adjust the electronic density of nickel selenide, allowing it to act as a cocatalyst, thus improving the catalytic activity in the UOR and MOR processes. The optimal UOR and MOR properties are achieved by adjusting the catalyst ratio and carbonization temperature. This experiment presents a straightforward synthetic method for creating a new rare-earth-based composite catalyst.

Water-Tolerant Boron-Substituted MCM-41 for Oxidative Dehydrogenation of Propane.

Boron-based catalysts for oxidative dehydrogenation of propane (ODHP) have displayed excellent olefin selectivity. However, the drawback of deboronation leading to catalyst deactivation limited their scalable applications. Hereby, a series of mesoporous B-MCM-41 (BM-x, B/Si = 0.015-0.147) catalysts for ODHP were prepared by a simple hydrothermal synthesis method. It was found that propane conversion was increased and the initial reaction temperature was reduced with an increase of boron content, and the optimal values appeared on BM-2.0 (B/Si = 0.062), while olefins' (ethylene and propylene) selectivity was maintained at ca. 70-80%. Most importantly, BM-1.0 (B/Si = 0.048) exhibited favorable activity, stability, and water tolerance after washing treatment or long-time operation (e.g., propane conversion of ca. 15% and overall olefin selectivity of ca. 80% at 550 °C) because its high structural stability prevented boron leaches. These features were identified by X-ray diffraction (XRD), N2 physisorption, inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy studies. The tri-coordinated B-OH species incorporated into the mesoporous silica framework are considered to be the active sites for ODHP.

[Active oxygen species of Co-V-O catalysts in propane oxidative dehydrogenation analyzed by FTIR and XPS spectra].

A series of Co-V-O (meta-CoV2O6, pyro-Co2 V2 O7, and ortho-Co3 V2 O8) catalysts were prepared by microwave oxalate co-precipitation method and characterized by (XRD), TEM, BET, FTIR, XPS, H2-TPR and conductivity measurement. The catalytic characters of the catalysts for propane oxidative dehydrogenation were investigated. The FTIR spectra of catalysts were obtained in the range of 400-1 100 cm(-1) and their major bands were assigned. The peak separation fitting of O(1s) XPS spectra was carried out and the quantity of oxygen species was calculated. The results of XRD characterization showed that pure meta-CoV2O6, pyro-Co2 V2O7, and ortho-Co3 V2O8 with nice structure were obtained. The TEM images demonstrated that the catalysts showed uniform particle with the mean particle size of 20-30 nm. The diagram of the relationship between electrical conductivity and oxygen partial pressure of Co3V2O8 and Co2 V2O7 showed dsigma/dPo2 > 0, which implied that these were p-type semiconductor, and CoV2O6 reverse showed dsigma/dPo2 < 0, which implied n-type semiconductor. 48.12%, 47.82% and 35.24% of C3 H6 selectivities were obtained for p-type semiconductor Co3 V2O8, CO2 V2O7 and n-type CoV2O6 catalysts respectively at 10% C3H6 conversion, and the results showed that p-type semiconductor catalysts Co3 V2O8 and Co2 V2O7 showed higher activity than n-type catalyst CoV2O6. The results of FTIR, XPS, H2-TPR and conductivity measurement indicated that transferring between non-stoichiometric and lattice oxygen that easily happened in Co3 V2O8 and Co2 V2O7 catalysts might promote the oxidation-reduction reaction between different valence vanadium species, and promoted the oxygen vacancy formation. Furthermore, the forming of Co-O-V bridge bond that was easy to shift between Co and V increased the mobile oxygen species of O2-, O2(2-) and O- and made the redox reaction among different valence V be realized. It is concluded that high catalytic properties of p-type semiconductor Co3 V2O8 and Co2 V2O7 can be attributed to the abundant oxygen species O- that existed in these catalysts.

[Study on performance of Ni3 V2O8 catalyst and analysis of X-ray photoelectron spectroscopy].

Ni3V2O8 catalyst was prepared by oxalate co-precipitation method with microwave heating in this paper. In order to study the relationship between the catalytic performance and the surface species, the catalyst was characterized by XRD, BET, H2-TPR, XPS, TEM and conductivity measurement. The surface property of Ni3V2O8 was studied by XPS and the catalytic performance of the oxidative dehydrogenation of propane to propylene was also investigated. The results of XRD showedthat pure Ni3V2O8 with nice structure was obtained. TEM experiments results demonstrated that the prepared Ni3V2O8 catalyst at 700 degrees C calcination showed uniform particle with the mean particle size of 30 nm. The surface area of the catalyst was 8.623 m2 x g(-1). The diagram of the relationship between electrical conductivity and oxygen partial pressure of Ni3V2O8 showed dsigma/dPO2, >0, implying that Ni3V2O8 catalyst was a p-type semiconductor. H2-TPR results showed that only one unsymmetrical reduction peak appeared at 663.5 degreesC within 300-900 degrees C region over Ni3V2O8 catalyst and no obvious shoulder peak was observed. It could also be found that the ratio of non complete reduction oxygen species was about 33.59% (O(-) 27.55%, O2(2-) 6.04%) from the O(1s) XPS result and more V4+ species existed on the Ni3V2O8 catalyst surface. The TPR and XPS results illustrated that the transformation of the lattice oxygen to non-complete reduction oxygen in NiV2O8 catalyst might promote the oxidation-reduction reaction between different valence vanadium and promoted the oxygen vacancy formation. This then led to abundant non-complete reduction oxygen O(-) and V4+ species formation on the surface of Ni3V2O8 catalyst. The active result of oxidative dehydrogenation of propane to propylene showed that the 60.02% propylene selectivity could be reached at 18.60% propane conversion. Compared with the reported results over the coexistent NiO and Ni3V2O8 system from the literature, pure Ni3V2O8 catalyst system in this present paper showed higher propylene selectivity than the coexistent NiO and Ni3V2O8 system under the same propane conversion condition, suggesting that the performance of propane to propene is correlated to the oxidation-reduction of V4+ / V5+ couple and non complete reduction oxygen species (O(-) or O2(2-)). This result further illustrated that NiV2O8 was active phase for oxidative dehydrogenation of propane to propylene. Combining the active and characterization results, it was found that catalytic activity was correlated to the surface non-complete reduction O(-) and V4+ species, which was beneficial to improving the propylene selectivity.