Mass spectra of negative ions in air-like gas mixtures at atmospheric pressure

We have obtained mass spectra of negative ions produced by rays in artificial air at atmospheric pressure (N₂: 80%, O₂: 20%, H₂O: 20–1500 ppm, CO₂: 0.2–300 ppm, NO, NO₂ 0.02 ppm). We observed two main categories: hydrates built on simple ions (O₂⁻, O₃⁻, OH⁻, CO₃⁻, CO₄⁻, HCO₃⁻, NO₂⁻, NO₃⁻), hydrates built on complex ions (NO_x⁻, HNO_γ, HCO₃⁻HNO_x, x = 2,3; Y = 2, 3). For high values of hygrometry, CO₂ content and ageing time (5 msec) we observe the disappearance of O₂⁻, O₃⁻, OH⁻ hydrates whereas the major part of the spectrum consists of complex ions.     

Differential capacitance of the platinum/aqueous-solution interphase

The differential capacitance of polycrystalline platinum in aqueous H₂SO₄ and NaOH solutions has been investigated as a function of bias potential. A capacitance minimum is observed at 0·56 V in H₂SO₄ and − 0·34 V in NaOH solution. There is strong evidence for the irreversible adsorption of oxygen/OH⁻ ions and oxide-film formation. Addition of n-butylamine hinders the adsorption of oxygen/OH⁻ ions and it is itself strongly adsorbed.     

Hydrothermal synthesis of Ba(Ti, Sn)O3 fine powders and dielectric properties of the corresponding ceramics

Fine powders of submicron-sized crystallites of BaTiO₃ were prepared at 85–130°C by the hydrothermal method, starting from TiO₂.ξH₂O gel and Ba(OH)₂ solution. The products obtained below 110°C incorporated considerable amounts of H₂O and OH⁻ in the lattice. As-prepared BaTiO₃ is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH⁻ ions. Hydrothermal reaction of SnO₂.ξH₂O gel with Ba(OH)₂ at 150–260°C gives rise to the hydrated phase, BaSn(OH)₆.3H₂O, due to the amphoteric nature of SnO₂.ξH₂O which stabilises Sn(OH)₆²⁻ anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH)₆.3H₂O converts to BaSnO₃ through an intermediate, BaSnO(OH)₄. Solid solutions of Ba(Ti,Sn)O₃ are directly formed from (TiO₂ + SnO₂)..ξH₂O gel up to 35 mol% SnO₂. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH)₆.3H₂O and BaTiO₃, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O₃. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O₃ ceramics are explained on the basis of the prevailing diffuse phase transition behaviour.     

NO decomposition and reduction by CH4 over Sr/La2O3

Both NO decomposition and NO reduction by CH₄ over 4%Sr/La₂O₃ in the absence and presence of O₂ were examined between 773 and 973 K, and N₂O decomposition was also studied. The presence of CH₄ greatly increased the conversion of NO to N₂ and this activity was further enhanced by co-fed O₂. For example, at 773 K and 15 Torr NO the specific activities of NO decomposition, reduction by CH₄ in the absence of O₂, and reduction with 1% O₂ in the feed were 8.3·10⁻⁴, 4.6·10⁻³, and 1.3·10⁻² μmol N₂/s m², respectively. This oxygen-enhanced activity for NO reduction is attributed to the formation of methyl (and/or methylene) species on the oxide surface. NO decomposition on this catalyst occurred with an activation energy of 28 kcal/mol and the reaction order at 923 K with respect to NO was 1.1. The rate of N₂ formation by decomposition was inhibited by O₂ in the feed even though the reaction order in NO remained the same. The rate of NO reduction by CH₄ continuously increased with temperature to 973 K with no bend-over in either the absence or the presence of O₂ with equal activation energies of 26 kcal/mol. The addition of O₂ increased the reaction order in CH₄ at 923 K from 0.19 to 0.87, while it decreased the reaction order in NO from 0.73 to 0.55. The reaction order in O₂ was 0.26 up to 0.5% O₂ during which time the CH₄ concentration was not decreased significantly. N₂O decomposition occurs rapidly on this catalyst with a specific activity of 1.6·10⁻⁴ μmol N₂/s m² at 623 K and 1220 ppm N₂O and an activation energy of 24 kcal/mol. The addition of CH₄ inhibits this decomposition reaction. Finally, the use of either CO or H₂ as the reductant (no O₂) produced specific activities at 773 K that were almost 5 times greater than that with CH₄ and gave activation energies of 21–26 kcal/mol, thus demonstrating the potential of using CO/H₂ to reduce NO to N₂ over these REO catalysts.     

In situ IR and pulse reaction studies on the active oxygen species over SrF2/Nd2O3 catalyst for oxidative coupling of methane

Pulse reaction method and in situ IR spectroscopy were used to characterize the active oxygen species for oxidative coupling of methane (OCM) over SrF₂/Nd₂O₃ catalyst. It was found that OCM activity of the catalyst was very low in the absence of gas phase oxygen, which indicated that lattice oxygen species contributed little to the yield of C₂ hydrocarbons. IR band of superoxide species (O₂⁻) was detected on the O₂-preadsorbed SrF₂/Nd₂O₃. The substitution of ¹⁸O₂ isotope for ¹⁶O₂ caused the IR band of O₂⁻ at 1128 cm⁻¹ to shift to lower wavenumbers (1094 and 1062 cm⁻¹), consistent with the assignment of the spectra to the O₂⁻ species. A good correlation between the rate of disappearance of surface O₂⁻ and the rate of formation of gas phase C₂H₄ was observed upon interaction of CH₄ with O₂-preadsorbed catalyst at 700 °C. The O₂⁻ species was also observed on the catalyst under working condition. These results suggest that O₂⁻ species is the active oxygen species for OCM reaction on SrF₂/Nd₂O₃ catalyst.     

Formation of singlet molecular oxygen associated with the formation of superoxide radicals in aqueous suspensions of TiO2 photocatalysts

The production and decay of singlet molecular oxygen (¹O₂) in TiO₂ photocatalysis were investigated by monitoring its phosphorescence under various reaction conditions. First, the effects of additives such as KBr, KSCN, KI, H₂O₂, and ethanol on the amount of ¹O₂ produced by photo excitation of P25 TiO₂ were measured. The same additives were employed to investigate the effect on the amount of O₂⁻ produced. Comparison between the effects on ¹O₂ and O₂⁻ suggested that ¹O₂ is formed by the electron transfer mechanism, the reduction of molecular oxygens to O₂⁻ by photogenerated electrons and the subsequent oxidation of O₂⁻ to ¹O₂ by photogenerated holes. The formation of ¹O₂ decreased at pH < 5 and pH > 11, indicating that the intermediate O₂⁻ is stabilized at the terminal OH site of the TiO₂ surface in the pH range of 5 < pH < 11. Eighteen commercially available TiO₂ photocatalysts were compared on the formation of ¹O₂ and O₂⁻ in an aqueous suspension system. The formation of ¹O₂ was increased with decreasing size of TiO₂ particles, indicating that a large specific surface area causes a higher possibility of reduction producing O₂⁻ and then a large amount of ¹O₂ is formed. The difference in the crystal phase (rutile and anatase) did not affect the formation of ¹O₂.     

The effect of oxygen concentration on the reduction of NO with propylene over CuO/γ-Al2O3

The effect of oxygen concentration on the pulse and steady-state selective catalytic reduction (SCR) of NO with C₃H₆ over CuO/γ-Al₂O₃ has been studied by infrared spectroscopy (IR) coupled with mass spectroscopy studies. IR studies revealed that the pulse SCR occurred via (i) the oxidation of Cu⁰/Cu⁺ to Cu²⁺ by NO and O₂, (ii) the co-adsorption of NO/NO₂/O₂ to produce Cu²⁺(NO₃⁻)₂, and (iii) the reaction of Cu²⁺(NO₃⁻)₂ with C₃H₆ to produce N₂, CO₂, and H₂O. Increasing the O₂/NO ratio from 25.0 to 83.4 promotes the formation of NO₂ from gas phase oxidation of NO, resulting in a reactant mixture of NO/NO₂/O₂. This reactant mixture allows the formation of Cu²⁺(NO₃⁻)₂ and its reaction with the C₃H₆ to occur at a higher rate with a higher selectivity toward N₂ than the low O₂/NO flow. Both the high and low O₂/NO steady-state SCR reactions follow the same pathway, proceeding via adsorbed C₃H₇---NO₂, C₃H₇---ONO, CH₃COO⁻, Cu⁰---CN, and Cu⁺---NCO intermediates toward N₂, CO₂, and H₂O products. High O₂ concentration in the high O₂/NO SCR accelerates both the formation and destruction of adsorbates, resulting in their intensities similar to the low O₂/NO SCR at 523–698 K. High O₂ concentration in the reactant mixture resulted in a higher rate of destruction of the intermediates than low O₂ concentration at temperatures above 723 K.     

Preparation of supported Pt-M catalysts (M = Mo and W) from anion-exchanged hydrotalcites and their catalytic activity for low temperature NO-H2-O2 reaction

The NO-H₂-O₂ reaction was studied over supported bimetallic catalysts, Pt-Mo and Pt-W, which were prepared by coexchange of hydrotalcite-like Mg-Al double layered hydroxides by Pt(NO₂)₄²⁻, MoO₄²⁻, and/or WO₄²⁻ and subsequent heating at 600 °C in H₂. The Pt–Mo interaction could obviously be seen when the catalyst after reduction treatment was exposed to a mixture of NO and H₂ in the absence of O₂. The Pt-HT catalyst showed the almost complete NO conversion at 70 °C, whereas the Pt-Mo-HT showed a negligible conversion. Upon exposure to O₂, however, Pt-Mo-HT exhibited the NO conversion at the lowest temperature of ≥30 °C, compared to ≥60 °C required for Pt-HT. EXAFS/XANES, XPS and IR results suggested that the role of Mo is very sensitive to the oxidation state, i.e., oxidized Mo species residing in Pt particles are postulated to retard the oxidative adsorption of NO as NO₃ and promote the catalytic conversion of NO to N₂O at low temperatures.     

The catalytic activity of FeOx/ZrO2 for the abatement of NO with propene in the presence of O2

FeO_x/ZrO₂ samples, prepared by impregnation with Fe(NO₃)₃, were characterised by means of DRS, XRD, FTIR, redox cycles and volumetric CO adsorption. Volumetric CO adsorption, combined with FTIR, showed that 45% of iron in the sample containing 2.8 Fe atoms nm⁻² was capable of forming iron carbonyls. DRS evidenced Fe₂O₃ on samples with Fe-content≥2.8 atoms nm⁻². The selective catalytic reduction of NO with C₃H₆ in the presence of O₂ was studied with a reactant mixture containing NO=4000 ppm, C₃H₆=4000 ppm, O₂=2%. The dependence on iron-content suggests that only isolated iron, prevailing in dilute FeO_x/ZrO₂, is active for NO reduction, whereas iron on the surface of small oxide particles, prevailing in concentrated FeO_x/ZrO₂, is active for C₃H₆ combustion.     

Propriétés chimiques et électrochimiques de l'eau dans les carbonates alcalins fondus

After recalling the acid—base and redox properties of the solvent species in fused alkaline carbonates, it is shown through potentiometric and thermogravimetric investigations that the acid—base system exchanging O²⁻ H₂O/2OH⁻ is weak, with an equilibrium constant K_A = p_CO2 × [OH⁻]²/p_H2O with pK_A = 1·5 ± 0·2. This result makes it possible to analyse the chemical transformation of fused carbonates into hydroxides under the influence of water vapour. The redox properties of hydrogen and its derivatives are next discussed with underlying thermodynamic considerations, taking into account the chemical and electrochemical experimental data.

With all of these data in mind, the operation of fuel cells containing fused carbonate electrolytes is explained. A new type of fuel cell is suggested, in which polarization due to proton transport to the electrodes is suppressed by the buffer effect of the acid—base pair H₂O/2OH⁻. Performances of such devices are compared to that of cells designed with a combustive mixture of oxygen and carbon dioxide.

Zusammenfassung

Nach einem Überblick auf das Säure/Basen- und Redox-Verhalten der Komponenten des Lösungsmittels in Schmelzen von Alkali-Karbonaten wird mittels potentiometrischer und thermogravimetrischer Untersuchungen gezeigt, dass das Säure/Basenpaar H₂O/2OH⁻, welches O²-austausct, eine Gleichgewichtskonstante K_A = P_CO2 × [OH⁻]²/P_H2O mit einem pKA = 1·5 ± 0·2 besitzt, also in diesem Lösungsmittel bei 600°C sehr schwach ist. Dieses Ergebnis erlaubt die Aufklärung der chemischen Umsetzung von Karbonaten in Schmelzen zu den entsprechenden Hydroxyden bei Einwirkung von Wasserdampf. Die Redoxeigenschaften des Wasserstoffs und seiner Verbindungen werden im folgenden auf Grund von thermodynamischen Betrachtungen diskutiert, indem von den vorgängig erhaltenen Resultaten und experimentellen chemischen und elektrochemischen Daten Gebrauch gemacht wird. Schliesslich wird die Gesamtheit der Ergebnisse verwendet, um eine Untersuchung des Verhaltens von Brennstoffzellen mit Karbonatschmelzen durchzuführen. Man beschreibt einen neuen Typ dieser Reihe, bei welchem die auf den Protonentransport zurückzuführenden Polarisationserscheinungen infolge des Puffereffektes des vorhandenen Säure/Basenpaares H₂O/2OH⁻ unterdrückt werden. Das Verhalten dieser Zellen wird mit demjenigen von Brennstoffzellen auf der Basis von Sauerstoff und Kohlendioxyd als Brennstoffen verglichen.     

Photocatalytic oxidation of CO with various oxidants by Mo oxide species highly dispersed on SiO2 at 293 K

The photocatalytic oxidation of CO into CO₂ with oxidants such as NO, N₂O and O₂ proceeded efficiently on a Mo/SiO₂ with high Mo dispersion under UV light irradiation. It was found that the reaction rate greatly depended on the kind and concentration of the oxidant. Photoluminescence investigations reveal the close relationship between the reaction rate and the relative concentration of the photo-excited Mo⁶⁺-oxide species, i.e. charge transfer–excited–triplet state (Mo⁵⁺–O⁻)^*, under steady-state reaction conditions. Moreover, the photocatalytic oxidation of CO with O₂ in excess H₂ was carried out to test suitability for applications to supplying pure H₂. This reaction was seen to proceed efficiently on Mo/SiO₂ with a high CO conversion of 100% and CO selectivity of 99% after 180 min under UV light irradiation, showing higher photocatalytic performance than TiO₂ (P-25) photocatalyst. UV–vis, XAFS, photoluminescence and FT-IR investigations revealed that the high reactivity of the charge transfer–excited–triplet state (Mo⁵⁺–O⁻)^*, with CO as well as the high reactivity of the photoreduced Mo-oxide species (Mo⁴⁺-species) with O₂ to produce the original Mo-oxide species (Mo⁶⁺O²⁻), played a crucial role in the reactions.     

NOx adsorption on MnO2/NaY composite: an in situ FTIR and EPR study

The NO, NO/O₂, and NO/O₂/H₂O adsorption on MnO₂/NaY (5 and 15 wt.% MnO₂) composite catalyst and NaY has been studied by means of in situ FTIR and EPR spectroscopy at elevated temperatures and during heating under reaction-like conditions. NO adsorption and co-adsorption of NO and O₂ on NaY and MnO₂/NaY proceeds via oxidation of NO forming NO₂⁻ and NO₃⁻ species. Whereas the manganese dioxide preferably acts as oxidising agent, the zeolite stores the NO_x species as nitrite and nitrate ions in the solid. In the presence of oxygen, the nitrate formation is enhanced due to additional oxidation of NO through gaseous oxygen leading to NO₂. Dimerisation of NO₂ to N₂O₄ and following disproportionation of the latter causes the formation of NO⁺ and NO₃⁻ species which are associated with nucleophilic zeolitic oxygen and especially alkali cations of the zeolite, respectively. The presence of oxygen facilitates reoxidation of Mn²⁺ which keeps more Mn ions in the active state. Pre-adsorbed water and higher amounts of water vapour in the feed hinder the NO adsorption by blocking the adsorption sites and shift the nitrate formation to higher temperatures. The quantities and thermal stability of the nitrates formed during NO and NO/O₂ adsorption differs which points to a different mechanism of nitrate formation. In the absence of gaseous oxygen, nitrates are formed by participation of only lattice oxygen. In the presence of oxygen, nitrate formation by dimerisation and disproportionation reactions of NO₂ dominates. The manganese component of the composite catalyst supports the oxidation of NO to nitrite and subsequently to nitrate. During this process Mn⁴⁺ is reduced to Mn²⁺ as evidenced by in situ EPR measurements.     

Untersuchung über die anionenadsorption mit hilfe markierter ionen

From previous work, the adsorption of anions is regarded as an essential factor for the different corrosion behaviour of metals in solutions containing different anions. Adsorption is measured by means of ³⁶Cl⁻, ⁸²Br⁻, ¹⁸ F⁻, ³⁶ClO₄⁻, ³⁵O₄²⁻, H³⁵S⁻ and ¹⁴CN⁻ on Pt, Ni and Fe in the form of sheets and evaporated films. Besides the determination of the adsorption after dipping into the solution, a method has been developed for the measurement of adsorption in contact with the solution and for the determination of its kinetics. The method can also be applied to O₂-free metal surfaces produced under vacuum. In this case, however, very rapid adsorption is observed, whereas normally saturation is reached only after many hours. It is concluded that, in general, exchange between oxygen on the metal and the anion takes place rather than simple adsorption.

The distribution of the anions adsorbed on the metal surface has been studied by autoradiography; adsorption takes place preferentially at the grain boundaries and increases when the crystal size decreases.

These results confirm the interpretation of passivation as a competition between various processes: metal dissolution, coverage by a passivating oxide film, and displacement of oxygen by anions.     

Surface reactivity of MgO oxygen vacancies

The interaction of gas-phase molecules (O₂, CO and H₂) with oxygen vacancies (F_s centers) on the MgO(1 0 0) surface was studied by cluster models ab initio wave functions. The F_s centers exhibit a high reactivity towards O₂, CO and H₂ at variance with the regular sites of the MgO surface. The reaction proceeds through the formation of radical anions, O⁻₂ and CO⁻, via the transfer of one electron trapped in the surface cavity to the empty levels of the adsorbed molecule, and can lead to the heterolytic dissociation of the H₂ molecule.     

Pore solution composition and reinforcement corrosion characteristics of microsilica blended cement concrete

Plain and microsilica blended cement pastes with water-cement ratio of 0.6 were prepared using a 14% C₃A cement. Two levels of chloride from NaCl corresponding to 0.6% and 1.2% by weight of cement were added through mix water. The pastes were allowed to hydrate in sealed containers for 180 days and then subjected to pore solution expression. The expressed pore fluids were analyzed for chloride and hydroxyl ion concentrations. The results show that the OH⁻ ion concentration in the pore solutions of both chloride-free and chloride-bearing pastes drop steeply with increasing cement replacement by microsilica. For 10% microsilica cement pastes the pH for both 0.6% and 1.2% chloride addition was found to be around 13.30. However, the pH drops to a level below that of saturated Ca(OH)₂ solution when cement replacement by microsilica is increased from 10% to 20%. This is ascribable to the consumption of Ca(OH)₂ by microsilica as shown by the DTA/TGA results. 10% and 20% microsilica blending more than doubles the free chloride ion concentration in the pore solutions of the chloride-bearing pastes. 10% microsilica replacement raises the Cl⁻/OH⁻ ratio 4 to 5 fold, whereas for 20% microsilica replacement, the Cl⁻/OH⁻ ratio is increased to 77 and 39 folds over the corresponding values for the plain cement pastes for 0.6% and 1.2% chloride additions respectively. Accelerated corrosion monitoring tests carried out on steel bars embedded in plain and microsilica blended cement concretes exposed to 5% NaCl solution show a 3 fold superior performance of microsilica blended cement concretes in terms of corrosion initiation time. This corrosion behaviour is contrary to the prediction from the increased aggressivity of pore solution composition in terms of highly elevated Cl⁻/OH⁻ ratios. This is attributable to the densification of cement matrix by the pozzolanic reaction between microsilica and calcium hydroxide. No discernable advantage in terms of corrosion initiation time is evident by increasing microsilica blending from 10% to 20%.     

Einfluss der säurekonzentration auf die anodische auflosung des indiumamalgams

The effect of HClO₄ concentration on the rate of electrode processes on a stationary indium amalgam electrode in stirred In(ClO₄)₃ solutions at constant ionic strength (3 M NaClO₄) has been investigated. Alongside with the measurement of polarization curves, the exchange current and the true rate of the anodic process of amalgam dissolution (i_a at different potentials (φ) were determined by a radiochemical method. With an increase in the HClO₄ concentration, a sharp decrease in the exchange current is observed; at HClO₄ concentrations below 0.2 M at constant φ, the i_a values are inversely proportional to the HClO₄ concentration. The experimental results are expressed by the equation p] i_a = k[In][H⁺]⁻¹ exp (βφF|RT),

where [In] is the concentration of the indium amalgam. The rate of the cathodic process at constant φ also decreases with a decrease in pH. A hypothesis is advanced according to which partially hydrolysed In(H₂O)₅OH²⁺ ions, rather than In(H₂O)₆³⁺ which are predominant in the solution, participate in the electrode process. The OH⁻ ions, like some other anions, appear to be capable of facilitating the transfer of electrons between the electrode surface and the reacting particle. An analysis of the results obtained (and of data in the literature) shows that partially hydrolysed metal ions play an essential role in electrode processes.     

Effect of anions and cations on the aqueous phase catalytic hydrogenation of C=C bonds

The influence of solution composition (nature of anions and cations, pH) in the aqueous phase catalytic hydrogenation of C=C bonds (maleic acid) has been investigated.

In weakly acidic solutions (of pH 3 and 6) the influence of the commonly used anions (ClO₄⁻, HSO₄⁻/SO₄²⁻, Cl⁻) is less important than that obtained in solutions of pH 0.3, found in previous works [Electrochim. Acta 45 (2000) 4299]. This difference can be ascribed to a weaker adsorption of the anion on platinum, as well as, to the different nature of the competitively adsorbed maleic acid species (molecular form or anionic adsorption) depending on the solution pH. In the presence of (hydrogeno)phosphates the lowest activities are obtained implying that these anions are the most strongly adsorbed on platinum.

An important promotion of platinum activity in the presence of cations has also been found. This effect depends on the size of the cation and can be attributed to the modification of the work function and, consequently, of the adsorption properties of platinum.     

Voltammetric study of halide ion adsorption on platinum in perchloric acid solutions

Periodic current/potential curves were taken potentiostatically at 30 mV/sec on smooth platinum in 1 N HClO₄ with different additions of HCl, HBr, and HI, in the potential range between hydrogen evolution and deposition of oxygen or of the respective halide ion. The effect of increasing halide ion concentration, starting at 10⁻⁶ M, on hydrogen adsorption and oxygen adsorption was studied systematically. Impedance measurements were made at 1000 c/s under the same conditions as the measurements of the current/potential curves. It is concluded from the dependence of the double layer capacitance upon the bulk concentration of halide ions in the double layer region that nearly a monolayer of adsorbed ions is present there for ₀c_Cl⁻ ≈ 10⁻² M, ₀c_Br ≈ 10⁻⁴ M, and ₀c_HI ≈ 10⁻⁵ M. The measurements at larger concentrations, especially for I⁻, show additional effects which are due to the deposition of halides and to the reverse reaction.     

Catalytic oxidation of sulfide ions over nickel hydroxides

The catalytic sulfide ion oxidation by oxygen to elemental sulfur over β-Ni(OH)₂ and LiNiO₂ has been studied. As a result of experimental investigation performed, a reaction mechanism is suggested which involves heterogeneous and homogeneous processes. Dioxygen activation in the heterogeneous process proceeds via a redox Ni²⁺ ↔ Ni³⁺ transition and participation of OH⁻ groups. The active HO⁻₂ species thus formed carries on the reaction in homogeneous phase. Nickel hydroxides are promising catalysts for practical application.     

Catalytic reduction of NO by propene over LaCo1−xCuxO3 perovskites synthesized by reactive grinding

One series of LaCo_1−xCu_xO₃ perovskites with high specific surface area was prepared by the new method designated as reactive grinding. These solids were characterized by N₂ adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), H₂-temperature programmed reduction (TPR), O₂-temperature programmed desorption (TPD), NO + O₂-TPD, C₃H₆-TPD, NO + O₂-temperature programmed surface reaction (TPSR) under C₃H₆/He flow as well as catalytic reduction of NO activity tests. The catalytic performance of unsubstituted sample is poor with a maximum conversion to N₂ of 19% at 500 °C at a space velocity of 55,000 h⁻¹ (3000 ppm NO, 3000 ppm C₃H₆, 1% O₂ in helium) but it is improved by incorporation of Cu into the lattice. A maximal N₂ yield of 46% was observed over LaCo_0.8Cu_0.2O₃ under the same conditions. Not only the abundance of -oxygen but also the mobility of β-oxygen of lanthanum cobaltite was remarkably enhanced by Cu substitution according to O₂-TPD and H₂-TPR studies. The better performance of Cu-substituted samples is likely to correspond to the essential nature of Cu and facility to form nitrate species in NO transformation conditions. In the absence of O₂, the reduction of NO by C₃H₆ was performed over LaCo_0.8Cu_0.2O₃, leading to a maximal conversion to N₂ of 73% accompanied with the appearance of some organo nitrogen compounds (identified as mainly C₃H₇NO₂). Subsequently, a mechanism involving the formation of an organic nitro intermediate, which further converts into N₂, CO₂ and H₂O via isocyanate, was proposed. Gaseous oxygen acts rather as an inhibitor in the reaction of NO and C₃H₆ over highly oxidative LaCo_0.8Cu_0.2O₃ due to the heavily unselective combustion of C₃H₆ by O₂.