The present work aims at investigating the catalytic decomposition of N 2 O over CuO-CeO 2 single or mixed oxides prepared by different synthesis routes, i.e., impregnation, precipitation and exotemplating. To gain insight into the particular role of CeO 2 as well as of CuO-CeO 2 interactions, three different types of materials are prepared and tested for N 2 O decomposition both in the absence and presence of excess O 2 : (i) bare CeO 2 prepared by precipitation and exotemplating, (ii) CuO/CeO 2 oxides synthesized by impregnation of CeO 2 samples prepared in (i) with CuO and iii) single stage synthesized CuO-CeO 2 mixed oxides employing the coprecipitation and exotemplating methods. The corresponding commercial samples were also examined for comparison purposes. All materials were characterized by N 2 adsorption at -196 °C, X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy (micro-Raman) and scanning electron microscopy (SEM). The results demonstrated the key role of preparation procedure on the direct catalytic decomposition of N 2 O. Among the bare CeO 2 samples, the best performance was obtained with the samples prepared by the precipitation method, followed by exotemplating, while commercial CeO 2 showed the lowest performance. All bare oxides demonstrated low N 2 O conversion, never exceeding 40% at 600 °C. Amongst the CuO-CeO 2 oxides, the optimum performance was observed for those prepared by co-precipitation, which achieved complete N 2 O conversion at 550 ºC. In the presence of excess oxygen in the feed stream, a slight degradation is observed, with the sequence of deN 2 O performance to remain unchanged. The superiority of Cu-Ce mixed oxides prepared by precipitation compared to all other materials can be mainly ascribed to their excellent redox properties, linked to Ce 4+ /Ce 3+ and Cu 2+ /Cu + redox pairs. A redox mechanism for N 2 O catalytic decomposition is proposed involving N 2 O adsorption on Cu + sites and their regeneration through Cu-ceria interactions. and mobile emissions is nowadays a challenging environmental issue.Several after-treatment techniques have been developed for N 2 O abatement, including thermal decomposition 6 , non-selective catalytic reduction 4 , selective catalytic reduction 7,8 and direct catalytic decomposition 9-12 . Among these, direct catalytic decomposition of N 2 O (deN 2 O) is the most promising method, due to its high efficiency and low energy requirements. The decomposition of N 2 O has been studied on various catalytic systems, such as transition and noble metal catalysts, perovskites, hexaluminates, spinels, zeolites, etc 4,9,[13][14][15][16][17][18][19][20] . In spite of the excellent catalytic performance of noble metals (NMs)-based catalysts, their high cost and sensitivity to oxygen poisoning limit their practical applications 9 . Therefore, the development of NMs-free catalysts of low cost and adequate de-N 2 O performance is of crucial importance from both practical ...

In this work we report on the combined impact of active phase nature (M: Co or Cu) and ceria nanoparticles support morphology (nanorods (NR) or nanocubes (NC)) on the physicochemical characteristics and CO2 hydrogenation performance of M/CeO2 composites at atmospheric pressure. It was found that CO2 conversion followed the order: Co/CeO2 > Cu/CeO2 > CeO2, independently of the support morphology. Co/CeO2 catalysts demonstrated the highest CO2 conversion (92% at 450 °C), accompanied by 93% CH4 selectivity. On the other hand, Cu/CeO2 samples were very selective for CO production, exhibiting 52% CO2 conversion and 95% CO selectivity at 380 °C. The results obtained in a wide range of H2:CO2 ratios (1–9) and temperatures (200–500 °C) are reaching in both cases the corresponding thermodynamic equilibrium conversions, revealing the superiority of Co- and Cu-based samples in methanation and reverse water-gas shift (rWGS) reactions, respectively. Moreover, samples supported on ceria nanocubes exhibited higher specific activity (µmol CO2·m−2·s−1) compared to samples of rod-like shape, disclosing the significant role of support morphology, besides that of metal nature (Co or Cu). Results are interpreted on the basis of different textural and redox properties of as-prepared samples in conjunction to the different impact of metal entity (Co or Cu) on CO2 hydrogenation process.

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The fine-tuning of CuO–CeO2 mixed oxides by means of synthesis procedure (co-precipitation) and alkali promotion (1.0 at Cs per nm2) towards highly active deN2O catalysts is demonstrated.