Surface Of Ni Particles Research Articles

Enhanced arc erosion and dynamic welding resistance of Ag-10 wt%Ni@Gr contact material

In this work, a novel hybrid reinforcement Ni@Gr was successfully synthesized by graphene in-situ grown on the surface of Ni particles, and the Ag-10 wt%Ni@Gr contact material was prepared by the combined methode of wet mixing and spark plasma sintering. The effect of graphene incorporation on the electrical performance of Ag-10 wt%Ni@Gr contact material was investigated, and the arc erosion mechanism was discussed as well. As compared to the Ag-10 wt%Ni contact material, the make-arc energy, break-arc energy and the maximum welding force of the Ag-10 wt%Ni@Gr contact material are decreased by 13.2 %, 4.9 %, and 23.1 %, respectively. Moreover, the Ag-10 wt%Ni@Gr contact material displays smaller erosion area, lower surface roughness and less mass loss. It can be ascribed to the increased elastic modulus of the contact surface, reduced bounce effect, lowered make-arc energy and shortened the make-arc duration that are stemmed from the incorporation of graphene. In addition, the incorporation of graphene contributes to the enhanced molten pool viscosity, which can effectively restrain Ag splashing, thereby enhancing arc erosion resistance and welding resistance.

Study of Ni/Y2O3/Polylactic Acid Composite.

This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle's surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.

Depositing Pd on the outmost surface of Pd1Ni/SiO2 single-atom alloy via atomic layer deposition for selective hydrogenation of acetylene

Supported Pd single-atom alloy (SAA) catalysts are selective in acetylene semi-hydrogenation. However, it is a challenge to prepare Pd SAA where Pd single atoms dispersed on the outmost surface of the catalysts because the Pd atoms on Pd SAA prepared by conventional impregnation distribute inside the alloyed particle or on the support surface after activation. In this work, we firstly synthesized Ni/SiO2 nanocatalysts by impregnation, followed by H2 reduction to generate metal Ni particles on SiO2. Subsequently, Pd single atoms are selectively deposited on the Ni particle surface by atomic layer deposition (ALD). The Pd species on the Pd1Ni/SiO2 prepared by ALD dispersed on the outmost surface of catalyst, presenting the improved catalytic performances in acetylene hydrogenation, as compared to a reference Pd1Ni/SiO2 catalyst prepared by impregnation. The Pd1Ni/SiO2 catalyst prepared by ALD with 5 cycles (0.04 wt. %Pd, 5c-Pd1Ni/SiO2) shows both superior hydrogenation activity (92 %) and selectivity (88 %) under mild temperature (80 °C) in the selective semi-hydrogenation of acetylene. Moreover, the specific activity of the 5c-Pd1Ni/SiO2 catalyst is the highest, as compared to the catalysts reported in literature. Therefore, we conclude that the metal single atoms on metal SAA catalyst prepared by ALD locate on the outmost surface of the catalyst, presenting the unusual catalytic performances in catalysis.

Size-Dependent Strong Metal–Support Interactions of Rutile TiO2-Supported Ni Catalysts for Hydrodeoxygenation of m-Cresol

A series of rutile TiO2-supported Ni catalysts with varying Ni sizes were prepared and reduced at 650 °C to explore the effect of Ni size on the strong metal–support interactions (SMSI) and its consequences on the hydrodeoxygenation (HDO) of m-cresol at 350 °C and atmospheric pressure. When the Ni size increases from 4 to 29.1 nm, the SMSI becomes stronger, e.g., the thickness of the TiOx overlayer and the coverage extent of TiOx on the Ni particle surface increase. Direct deoxygenation to toluene is the dominant pathway on Ni/TiO2 catalysts with varying Ni loadings, with almost no CH4 being formed. These results indicate that the TiOx overlayer significantly alters the property of Ni. That is, the C-C hydrogenolysis activity on bare Ni is completely inhibited due to SMSI, while the deoxygenation activity is improved at the Ni-TiOx interfacial perimeter sites. Meanwhile, the turnover frequency of HDO on small Ni particles of 4 nm is > 2 times higher than that on large Ni particles of 29.1 nm, indicating that the small Ni particle with moderate SMSI appears to be optimal for the direct deoxygenation of m-cresol to toluene. The results suggest HDO activity may be enhanced by tuning the metal particle size and SMSI degree.

Towards synchronously improving dielectric performance and thermal conductivity in Ni/PVDF by tailoring core-shell structured Ni@NiO particles

An insulating interlayer between conductive particles and polymer is crucial for preparing polymer dielectrics with high dielectric permittivity ( ε) but low loss and high breakdown strength ( Eb). To restrain the large loss of raw nickel (Ni)/poly (vinylidene fluoride) (PVDF) composites when still maintaining a high- ε at the percolation threshold ( fc) of conductive fillers, in this work, nanoscale nickel oxide (NiO) shell with diverse thickness was coated around the surface of Ni particles via a facile thermal calcination at 650°C under air, and the gained Ni@NiO particles were composited with PVDF to produce morphology-controllable high- ε, low loss composites. The influences of the NiO shell and thickness on the dielectric performances and thermal conductivity (TC) of the composites were investigated in terms of filler loading and frequency. Compared with raw Ni/PVDF, the Ni@NiO/PVDF composites exhibit remarkably suppressed dielectric loss and enhanced Eband TC because the NiO interlayer not only prevents the Ni particles from direct contact and hinders the long-range electron migration thereby resulting in rather low leakage current, but also simultaneously suppresses thermal interfacial resistance and enhances interfacial compatibility between the fillers and the matrix subsequently resulting in improved TC. Therefore, the Ni@NiO/PVDF with high ε-low loss, heightened Eband TC present appealing potential applications in microelectronics and electrical industries.

Boosting Amination of 1‐Octanol to 1‐Octylamine via Metal‐Metal Oxide Interactions in NixFe1/Al2O3 Catalysts

AbstractThe synthesis of 1‐octylamine, a primary platform molecule, remained a great challenge in catalysis. In this work, NixFe1/Al2O3 was used for direct amination of 1‐octanol to 1‐octylamine. Catalyst evaluation indicated that the promotion effect of Fe/Ni ratio on the catalytic amination activity followed a volcano curve while the selectivity to 1‐octylamine was positively correlated with the Fe loading. Compared with the Ni/Al2O3 catalyst, the amination activity was increased by 2.8 times by optimizing the Fe/Ni ratio to 0.33, and the selectivity to 1‐octylamine was increased from 84.0 % to 96.3 % when increasing the Fe/Ni ratio from 0 to 1. Based on catalyst characterizations, the good performance of NixFe1/Al2O3 was ascribed to the combined modification effect of the NiFe alloy and Ni−FeOx interface. The FeOx species enriched on the Ni particle surface provided sufficient Fe2+/Fe3+−O2− sites for the activation of 1‐octanol, and the cooperation between Ni sites and Lewis acid‐base pairs enhanced the amination of 1‐octanol to 1‐octylamine. This work sheds new light on the design of Ni‐based catalysts without using a noble metal for primary amine preparation.

Dual Nanoislands on Ni/C Hybrid Nanosheet Activate Superior Hydrazine Oxidation‐Assisted High‐Efficiency H2 Production

AbstractClean hydrogen evolution through electrochemical water splitting underpins various innovative approaches to the pursuit of sustainable energy conversion technologies, but it is blocked by the sluggish anodic oxygen evolution reaction (OER). The hydrazine oxidation reaction (HzOR) has been considered as one of the most promising substitute for OER to improve the efficiency of hydrogen evolution reaction (HER). Herein, we construct novel dual nanoislands on Ni/C hybrid nanosheet array: one kind of island represents the part of bare Ni particle surface, while the other stands for the part of core–shell Ni@C structure (denoted as Ni‐C HNSA), in which exposed Ni atoms and Ni‐decorated carbon shell perform as active sites for HzOR and HER respectively. As a result, when the current density reaches 10 mA cm−2, the working potentials are merely −37 mV for HER and ‐20 mV for HzOR. A two‐electrode electrolyzer exhibits superb activity that only requires an ultrasmall cell voltage of 0.14 V to achieve 50 mA cm−2.

Dual Nanoislands on Ni/C Hybrid Nanosheet Activate Superior Hydrazine Oxidation-Assisted High-Efficiency H2 Production.

Clean hydrogen evolution through electrochemical water splitting underpins various innovative approaches to the pursuit of sustainable energy conversion technologies, but it is blocked by the sluggish anodic oxygen evolution reaction (OER). The hydrazine oxidation reaction (HzOR) has been considered as one of the most promising substitute for OER to improve the efficiency of hydrogen evolution reaction (HER). Herein, we construct novel dual nanoislands on Ni/C hybrid nanosheet array: one kind of island represents the part of bare Ni particle surface, while the other stands for the part of core-shell Ni@C structure (denoted as Ni-C HNSA), in which exposed Ni atoms and Ni-decorated carbon shell perform as active sites for HzOR and HER respectively. As a result, when the current density reaches 10 mA cm-2 , the working potentials are merely -37 mV for HER and -20 mV for HzOR. A two-electrode electrolyzer exhibits superb activity that only requires an ultrasmall cell voltage of 0.14 V to achieve 50 mA cm-2 .

Impact of Al2O3 Particle Size on the Open Porosity of Ni/Al2O3 Composites Prepared by the Thermal Oxidation at Moderate Temperatures

The performance of attractive Ni-based composites can be affected by changing their microstructures, e.g., introducing pores. Here, we report a novel, relatively low-cost process to fabricate Ni/Al2O3 composites with open porosity modified by the size of Al2O3 particles. The mixture of powders was subjected to thermal oxidation twice in air after a maximal temperature of 800 °C was reached in a stepwise manner and maintained for 120 min. The oxidation kinetics were determined thermogravimetrically. The open porosity was evaluated by an Archimedes’ principle-based method. Localization and quantification of NiO, newly formed on the Ni particle surface and acting as a mechanical bonding agent, were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. Larger ceramic particles prevented merging of NiO layers on adjacent Ni particles more efficiently; therefore, the open porosity increased from 21% to 24.2% when the Al2O3 particle diameter was increased from 5–20 µm to 32–45 µm. Because both Ni/Al2O3 composites exhibited similar flexural strength, the composite with larger Al2O3 particles and the higher open porosity could be a better candidate for infiltration by molten metal, or it can be directly used in a variety of filtration applications.

Tuning reverse water gas shift and methanation reactions during CO2 reduction on Ni catalysts via surface modification by MoOx

Catalytic reduction of CO2 to CO via reverse water gas shift (RWGS) reaction provides a feasible approach to utilize CO2, since CO can be further converted to various versatile products through the syngas routes. Ni-based catalysts are low cost and have a high activity for CO2 reduction but are nonselective for RWGS due to competition from methanation. In this work, we demonstrated that surface modification of Ni by MoOx can be tailored to tune the reactions of RWGS and methanation. The addition of MoOx improves Ni dispersion through strong interactions whereas partially reduced MoOx modifies the surface of Ni particles through both geometric coverage and electronic modification. No CO adsorption was observed at room temperature on the NiMo catalyst with a Mo/Ni ratio of 1, confirmed by density functional theory calculation. Tracking product evolution showed that CO2 is first reduced to CO through RWGS on the Ni catalysts and methane is a product of CO hydrogenation. Apparent activation energy analysis indicates that the overall reaction is controlled by CO desorption. Addition of a small amount of Mo (Mo/Ni ratio of 0.1) shifts the reaction further to methanation selective with ∼100% CH4 selectivity as MoOx aids in the activation of both CO2 and CO. In contrast, the addition of a large amount of Mo (Mo/Ni ratio of 1) shifts the reaction to RWGS selective with a CO selectivity > 94%. This is attributed to the enhanced CO desorption from the surface as a result of MoOx modification.

Ni particle surface descriptor to enhance roughness of Ni internal electrode in MLCCs

The uniform and continuous nickel internal electrode is crucial in high capacity and highly reliable multi-layer ceramic capacitors (MLCCs). However, the mechanism and the key factors that affect the roughness of the electrode have not been investigated thoroughly. Thus, seeking suitable descriptors that describe the most influential element which decides the roughness is required for the logical design of the Ni paste. In this study, we analyzed the surface of nickel powders and compared their electrode roughness in the aspects of the surface carbon species on nickel nanoparticles. As the increase in the relative C–O/C–C and C=O/C–C ratios, the relative electrode roughness of C-Ni-1, C-Ni-2, C-Ni-3, and C-Ni-4 increased from 1.00, 1.29, 1.54 to 2.51. Thus, low contents of C–O and C=O on the surface of Ni particles could improve the uniformity of the electrode. This study suggests a valuable perspective to reveal the decisive component to build the optimum surface of nickel nanoparticles for uniform internal electrodes in MLCCs.

CO Methanation on Mesoporous Ni–VOx/FDU‐12 Catalyst: Effects of the VOx Promoter on Low‐Temperature Activity

Herein, a series of Ni–VOx/FDU‐12 catalysts are prepared by an incipient impregnation method with FDU‐12 (cubic, Fm‐3m) as the support. The samples are characterized by nitrogen adsorption, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, H2‐temperature programmed reduction, and X‐ray photoelectron spectroscopy. Among all catalysts, Ni–VOx/FDU‐12 with NiO of 10 wt% and V2O5 of 2 wt% (10N2VF) show the best catalytic performance, which reaches maximum CO conversion and CH4 yield of 99.4% and 89%, respectively, at 325 °C. The lifetime test is conducted at a constant temperature of 450 °C for 100 h at 0.1 MPa and a high weight hourly space velocity (WHSV) of 60 000 mL g−1 h−1. The 10N2VF exhibit high antisintering and coking properties. The addition of the vanadium promoter improve Ni dispersion and change Ni electron density, which enhance the low‐temperature ability for CO dissociation via the weakening of CO linkage. In contrast, a large number of oxygen vacancies formed by the oxidation–reduction cycle of V5+/V4+/V3+ can enhance the dissociation of the by‐product CO2 and generate oxygen intermediates, which prevent carbon deposition on the surface of Ni particles.

Performance of a Direct Methane Solid Oxide Fuel Cell Using Nickel-Ceria-Yttria Stabilized Zirconia as the Anode.

A nickel-ceria-yttria stabilized zirconia (Ni-CYSZ) cermet material was synthesized and tested as the anode for the direct oxidation of methane in a solid oxide fuel cell (SOFC) with YSZ as the electrolyte and strontium-doped lanthanum manganite (LSM) as the cathode. Initially, the electrochemical behavior was investigated under several load demands in wet (3% H2O) CH4 at 850 °C during 144 h using I-V curves, impedance spectra, and potentiostatic measurements. Long-term tests were subsequently conducted under 180 mA·cm–2 in wet CH4 for 236 h and dry CH4 for 526 h at 850 °C in order to assess the cell stability. Material analysis was carried out by SEM-EDS after operation was complete. Similar cell performance was observed with wet (3% H2O) and dry CH4, and this indicates that the presence of water is not relevant under the applied load demand. Impedance spectra of the cell showed that at least three processes govern the direct electrochemical oxidation of methane on the Ni-CYSZ anode and these are related to charge transfer at high frequency, the adsorption/desorption of charged species at medium frequency and the non-charge transfer processes at low frequency. The cell was operated for more than 900 h in CH4 and 806 h under load demand, with a low degradation rate of ~0.2 mV·h–1 observed during this period. The low degradation in performance was mainly caused by the increase in charge transfer resistance, which can be attributed to carbon deposition on the anode causing a reduction in the number of active centers. Carbon deposits were detected mostly on the surface of Ni particles but not near the anode/electrolyte interface or the cerium surface. Therefore, the incorporation of cerium in the anode structure could improve the cell lifetime by reducing carbon formation.

Rapidly Solidified Aluminium Alloy Composite with Nickel Prepared by Powder Metallurgy: Microstructure and Self-Healing Behaviour.

Composite material prepared by spark plasma sintering (SPS) from a powder mixture of AlCrFeSi rapidly solidified alloy and 5 wt. % of Ni particles was studied in this work. It was proven that during SPS compaction at 500 °C, no intermetallic phases formed on the surface of Ni particles. The material exhibited sufficient mechanical properties obtained by tensile testing (ultimate tensile stress of 203 ± 4 MPa, ductility of 0.8% and 0.2% offset yield strength of 156 ± 2 MPa). Tensile samples were pre-stressed to 180 MPa and annealed at 450 and 550 °C for 1 h. Annealing at 450 °C did not lead to any recovery of the material. Annealing at 550 °C caused the full recovery of 0.2% offset yield strength, while the ductility was decreased. The self-healing behaviour originates from the growth of intermetallic phases between the Ni particle and the Al matrix. The sequence of NiAl, Ni2Al3 and NiAl3 intermetallic phases formation was observed. In particular, the morphology of the NiAl3 phase, growing in thin dendrites into the Al matrix, is suitable for the closing of cracks, which pass through the material.

Methane Activation on Bimetallic Catalysts: Properties and Functions of Surface Ni−Ag Alloy

AbstractThe paper presents a fundamental study of the properties and functions of well‐defined Ni−Ag surface alloys in methane decomposition and steam reforming, aiming at providing a better understanding of the principle for manipulating the catalytic activity of steam reforming and suppressing carbon formation. A better insight of structure‐property relationship was obtained by a kinetic study of the reactions on well‐defined surface Ni−Ag alloys, which were synthesized by surface redox reaction to selectively introduce Ag atoms into the surface of Ni particles supported on hydrotalcite derived support. The effects of Ni surface alloy with Ag are three‐folds in general. Replacement of Ni by Ag reduces the number of active site exponentially with increasing Ag site coverage. Ag site is not only inactive, but also significantly reduces the activity of adjacent Ni sites for methane activation in both methane decomposition and steam reforming. The third effect is to block the active sites for the nucleation and growth of the filamentous carbon. The rate of methane activation at Ni step sites was found to be 16–19 times of that on Ni terrace sites. The carbon formation rate decreased linearly with Ag site coverage and the effect of Ag is divided into two regions. At low Ag site coverages (0 to 0.055), Ag atoms preferentially deposit on Ni step sites, which has a significant effect on the methane activation compared to Ag atoms on the Ni terrace sites. The results reveal that the effects of Ag site on the carbon formation in the two regions are mostly caused by the different effects of Ag on the activity of Ni step sites and terrace sites, respectively, rather than the different ensemble sizes for carbon formation proposed in the literature.

Water-saving dry methanation for direct conversion of syngas to synthetic natural gas over robust Ni0.1Mg0.9Al2O4 catalyst

Production of synthetic natural gas (SNG) from coal is typically water intensive due to the need of increasing H2/CO ratio from 1 to 3 via water gas shift reaction. Here we report a water-saving dry methanation reaction that allows direct conversion of low H2 content syngas (H2/CO = 1) to methane without consumption of water for adjusting H2/CO to ≥ 3 and without production of waste water. Conventional Ni/Al2O3 catalyst is active for the dry methanation reaction but deactivates very rapidly due to carbon deposition and metal sintering. A Ni0.1Mg0.9Al2O4 catalyst exhibits much higher activity and better stability during steady state catalytic reaction and cyclic reaction-regeneration operations. Using a suite of characterization tools including BET, XRD, STEM, TEM, H2-TPR, Raman, TG-DSC, CO2 and NH3 TPD, and temperature-programmed hydrogenation, we reveal that carbon deposition did not occur on the surface of Ni particles in Ni0.1Mg0.9Al2O4 catalyst. Moreover, the population of small Ni nanoparticles (ca. 2 nm) increased after multiple reaction-regeneration operations possibly due to Ni redispersing via reversible diffusing among the framework of spinel. The exposure of active Ni surface and the formation of small-sized Ni nanoparticles together contributed to the stable and improved activity for dry methanation during the reaction-regeneration operations.

Hydrogen Production from Chemical Looping Reforming of Ethanol Using Ni/CeO2 Nanorod Oxygen Carrier

Chemical looping reforming (CLR) technique is a prospective option for hydrogen production. Improving oxygen mobility and sintering resistance are still the main challenges of the development of high-performance oxygen carriers (OCs) in the CLR process. This paper explores the performance of Ni/CeO2 nanorod (NR) as an OC in CLR of ethanol. Various characterization methods such as N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (TPR), and H2 chemisorption were utilized to study the properties of fresh OCs. The characterization results show the Ni/CeO2-NR possesses high Ni dispersion, abundant oxygen vacancies, and strong metal-support interaction. The performance of prepared OCs was tested in a packed-bed reactor. H2 selectivity of 80% was achieved by Ni/CeO2-NR in 10-cycle stability test. The small particle size and abundant oxygen vacancies contributed to the water gas shift reaction, improving the catalytic activity. The covered interfacial Ni atoms closely anchored on the underlying surface oxygen vacancies on the (111) facets of CeO2-NR, enhancing the anti-sintering capability. Moreover, the strong oxygen mobility of CeO2-NR also effectively eliminated surface coke on the Ni particle surface.

Effects of Ni particle morphology on cell performance of Na/NiCl2 battery

Electrochemical reaction of Ni particle, one of active cathode materials in the Na/NiCl2 battery, occurs on the particle surface. The NiCl2 layer formed on the Ni particle surface during charging can disconnect the electron conduction path through Ni particles because the NiCl2 layer has very low conductivity. The morphology and size of Ni particles, therefore, need to be controlled to obtain high charge capacity and excellent cyclic retention. Effects of the Ni particle size on the cell performance were investigated using spherical Ni particles with diameters of 0.5 μm, 6 μm, and 50 μm. The charge capacities of the cells with spherical Ni particles increased when the Ni particle size becomes smaller because of their higher surface area but their charge capacities were significantly decreased with increasing cyclic tests owing to the disconnection of electron conduction path. The inferior cyclic retention of charge capacity was improved using reticular Ni particles which maintained the reliable connection for the electron conduction in the Na/NiCl2 battery. The charge capacity of the cell with the reticular Ni particles was higher than the cell with the small-sized spherical Ni particles approximately by 26% at 30th cycle.

Atomically Dispersed Pt on the Surface of Ni Particles: Synthesis and Catalytic Function in Hydrogen Generation from Aqueous Ammonia–Borane

The development of cost-effective and highly efficient catalysts is of scientific importance and practical need in the conversion and utilization of clean energy. One of the strategies fulfilling that demand is to achieve high exposure of a catalytically functional noble metal to reactants to maximize its utilization efficiency. We report herein that the single-atom alloy (SAA) made of atomically dispersed Pt on the surface of Ni particles (Pt is surrounded by Ni atoms) exhibits improved catalytic activity on the hydrolytic dehydrogenation of ammonia–borane, a promising hydrogen storage method for onboard applications. Specifically, an addition of 160 ppm of Pt leads to ca. 3-fold activity improvement in comparison to that of pristine Ni/CNT catalyst. The turnover frequency based on the isolated Pt is 12000 molH2 molPt–1 min–1, which is about 21 times the value of the best Pt-based catalyst ever reported. Our simulation results indicate that the high activity achieved stems from the synergistic effect bet...

Interaction of CO, NO, and H2 molecules on the surface of a Ni/MgO(111) metal oxide system

The adsorption and interaction of carbon monoxide (CO), nitrogen oxide (NO), and hydrogen (H2) molecules on the surface of a system produced when nanosize nickel clusters are formed on the surface of a magnesium oxide film [MgO (111)] has been studied in an ultrahigh vacuum by IR, thermal desorption, and photoelectron spectroscopy. It is shown that, at a substrate temperature of 85 K, CO and NO molecules at low surface concentrations, are mostly adsorbed on the surface of Ni particles, whereas at higher surface coverage CO molecules are forced to the Ni/MgO(111) interface. The adsorption of hydrogen results in NO molecules also being displaced to the interface. The particular state of the molecules at the interface between the metal and the polar surface of the oxide is responsible for the observed processes in which CO is converted to CO2 due to the reduction of NO to N2.