The development of non-noble metal catalysts for low-temperature CO oxidation is a pivotal subject in various disciplines. In this study, an optimized Mn-doped NiO catalyst (Mn-NiO-0.5), prepared via aerosol pyrolysis with an equal molar ratio of Ni to Mn, demonstrates remarkable performance. It achieves an 82 % CO conversion at -20 °C and a 100 % conversion between 10 °C and 800 °C. The catalyst’s turnover frequency ( TOF ) for CO oxidation significantly surpasses that of previously reported noble-metal-based catalysts, underscoring its superior efficiency. Dynamic analyses suggest that the enhanced catalytic activity is a result of the unique atom burr structure, which presents an extensive surface area replete with abundant active sites. This structural feature is instrumental in maximizing the catalyst’s interaction with CO molecules. Experimental findings, corroborated by density functional theory (DFT) calculations, elucidate the mechanism of CO oxidation on the Mn-NiO-0.5 catalyst. The process is facilitated by the synergistic action of bimetallic sites, where the Ni–OH site acts as the primary adsorption point for CO. Subsequently, the CO is oxidized to bicarbonate through the interaction with the oxygen (O or O 2 ) at adjacent Mn sites. This pioneering study introduces a paradigm-shifting insight: the effectiveness of non-noble metal oxide catalysts can now compete with, and in some cases, outperform their noble metal counterparts. This breakthrough is set to transform the industry, presenting a compelling alternative to conventional noble metal catalysts and propelling the evolution of state-of-the-art environmental conservation technologies.
This study introduces a novel catalyst system comprising Pd nanoparticles loaded onto Mn-doped NiO for the efficient oxidation of methane (CH 4 ) at low temperatures. The loading of Pd nanoparticles onto the Mn-doped support has yielded a catalyst with exceptional activity and stability, as evidenced by the lowest T 50 temperature of 276 °C and a CH 4 conversion reaching 97% at 325 °C. The catalyst demonstrates optimized reaction kinetics with the lowest activation energy of 69.2 kJ mol –1 . The catalyst's superior performance is attributed to the synergistic effects of the Pd/Mn-NiO composite, which include a higher Pd 2+ /Pd 4+ ratio, increased adsorptive oxygen concentration (O ads /O total ), and a reduced Ni 3+ /Ni 2+ ratio. These characteristics collectively enhance the catalytic activity for CH 4 oxidation. The Mars-van Krevelen mechanism underpins the oxidation process, with Pd 2+ identified as the principal active site for CH 4 adsorption and dissociation. Diffuse reflectance infrared Fourier transform spectroscopy coupled with mass spectrometry elucidates the pathway of surface reactive oxygen species in the formation of key intermediates, such as formates, and underscores the accelerated decomposition of carbonate facilitated by the Pd modification on the Mn-NiO surface. The findings signify a significant advancement in the development of catalysts for environmental and energy-related applications, particularly in the mitigation of CH 4 emissions.
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