In the present work, nanowire morphologies of α-MnO, cobalt monodoped α-MnO, Cu and Co bidoped α-MnO, and Ni and Co bidoped α-MnO samples were prepared by a facile hydrothermal synthesis. The structural, morphological, surface, and redox properties of all the as-prepared samples were investigated by various characterization techniques, namely, scanning electron microscopy (SEM), transmission and high resolution electron microscopy (TEM and HR-TEM), powder X-ray diffraction (XRD), N sorption surface area measurements, X-ray photoelectron spectroscopy (XPS), hydrogen-temperature-programmed reduction (H-TPR), and oxygen-temperature-programmed desorption (O-TPD). The soot oxidation performance was found to be significantly improved via metal mono- and bidoping. In particular, Cu and Co bidoped α-MnO nanowires showed a remarkable improvement in soot oxidation performance, with its T (50% soot conversion) values of 279 and 431 °C under tight and loose contact conditions, respectively. The soot combustion activation energy for the Cu and Co bidoped MnO nanowires is 121 kJ/mol. The increased oxygen vacancies, greater number of active sites, facile redox behavior, and strong synergistic interaction were the key factors for the excellent catalytic activity. The longevity of Cu and Co bidoped α-MnO nanowires was analyzed, and it was found that the Cu/Co bidoped α-MnO nanowires were highly stable after five successive cycles and showed an insignificant decrease in soot oxidation activity. Furthermore, the HR-TEM analysis of a spent catalyst after five cycles indicated that the (310) crystal plane of α-MnO interacts with the soot particles; therefore, we can assume that more-reactive exposed surfaces positively affect the reaction of soot oxidation. Thus, the Cu and Co bidoped α-MnO nanowires provide promise as a highly effective alternative to precious metal based automotive catalysts.

Catalysts based on MCM-41 decorated with 35–70 nm diameter Ni particles were tested for the production of hydrogen by catalytic decomposition of methane (CDM). About 122 N m3 (molNi)−1 hydrogen yield was achieved over a catalyst comprised of optimized Ni loading of 50 wt % Ni/MCM-41. The H2 yield increased dramatically to 204 N m3 (molNi)−1, upon modification with 10 wt % Cu. The presence of Cu, in contact to Ni, appeared to reduce the sintering and coking of the active Ni sites, which enhanced the longevity of the catalyst. Raman analysis of the catalysts recovered after CDM experiments revealed that doping of Cu to Ni/MCM-41 enhanced the graphitic carbon deposition over the catalyst. All of the samples (Ni and Ni–Cu-modified MCM-41) were characterized by H2 chemisorption, SEM/TEM, XPS, XRD, H2-TPR, N2O titration, and Raman spectroscopy to examine the bulk and surface properties of the catalysts.

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