Interaction of Cobalt Nanoparticles with Oxygen- and Nitrogen-Functionalized Carbon Nanotubes and Impact on Nitrobenzene Hydrogenation Catalysis

Abstract

The type and the amount of functional groups on the surface of carbon nanotubes (CNTs) were tuned to improve the activity of supported Co nanoparticles in hydrogenation catalysis. Surface nitrogen species on CNTs significantly promoted the decomposition of the cobalt precursor and the reduction of cobalt oxide, and improved the resistance of metallic Co against oxidation in ambient atmosphere. In the selective hydrogenation of nitrobenzene in the gas phase, Co supported on CNTs with the highest surface nitrogen content showed the highest activity, which is ascribed to the higher reducibility and the lower oxidation state of the Co nanoparticles under reaction conditions. For Co nanoparticles supported on CNTs with a smaller amount of surface nitrogen groups, a repeated reduction at 350 °C was essential to achieve a comparable high catalytic activity reaching 90% conversion at 250 °C, pointing to the importance of nitrogen species for the supported Co nanoparticles in nitrobenzene hydrogenation.

Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

“…Similar effects on particle shape were observed for Pd when varying the acid-base character of the surface by functionalization with oxygen or nitrogen containing groups [163]. In general, the interaction with the N-containing functional groups promotes the catalytic activity of the metal [164][165][166].…”

“…In the case of PdCx, a high selectivity was observed for the conversion of acetylene to ethylene compared to a Pd/Al2O3 catalyst [166]. Notably, carbide formation occurs in flowing H2 between 120 °C and 300 °C, conditions often employed when synthesizing catalysts.…”

Co-based heterogeneous catalysts from well-defined α-diimine complexes: Discussing the role of nitrogen

“…Among the various dopants, nitrogen attracted most interest [15,[20][21][22]. and applications of transition metal/N-doped graphene (NGr) based catalytic systems ranges from oxygen reduction reactions (ORR) [23][24][25][26], hydrogen evolving reactions (HER) [27,28], photocatalysis [29,30], oxidation [31][32][33][34][35][36][37][38], and reduction [39][40][41][42][43][44] reactions of organic molecules, C-C bond formation [45] to many others [46][47][48][49][50][51]. Hence, merging rationally-designed suitable modified supports with cheap transition metals permits access to the design of active, selective and cheap catalytic materials thus allowing to match or to outperform noble-metal-based catalysts.…”

Co3O4–MnO2–CNT Hybrids Synthesized by HNO3 Vapor Oxidation of Catalytically Grown CNTs as OER Electrocatalysts

“…The peaks at approximately 44.3 and 51.58 can be assigned to the (111)a nd (2 00)r eflections of metallicC o. [11] Other samples were synthesizedb yv arying the growth timef rom 5t o1 20 min and the corresponding XRD patterns are shown in …”

“…The peaks at 2q = 19.1 (111), 36.9 (3 11), 38.6 (2 22), 44.9 (4 00), 59.3 (5 11), and 65.28 (4 40)s how the overlapping of the reflections of cubic Co 3 O 4 and cubic lMnO 2 .A dditional peaks at approximately 31.3 and 55.78 can be assigned to the (2 20)a nd (4 22)r eflections of Co 3 O 4 ,r espectively,a nd the peak at approximately 49.48 can originate from the (3 11)r eflection of lMnO 2 . [11,14] The formation of Co 3 O 4 can be explained by the exposure of encapsulatedC ot ot he corrosive HNO 3 vapor resulting in its oxidation, whereas MnO is concomitantly oxidized to MnO 2 .H ence, an oxide-carbon hybrid,t hat is, Co 3 O 4 -MnO 2 -OCNTswas obtained by the oxidizing vapor treatment.…”