Exploring the Effect of Co₃O₄ Nanocatalysts with Different Dimensional Architectures on Methane Combustion

Abstract

We fabricated Co 3 O 4 catalysts with different spatial structures, such as zero-dimensional (nanoparticles), one-dimensional (nanorods), two-dimensional (nanoplates), and three-dimensional (mesoporous and microporous) structures, for methane combustion. The Co 3 O 4 catalysts with different dimensional architectures demonstrated different activitiesf or the breaking of the CÀHb ond of methane. In particular, Co 3 O 4 with 2D structure gave rise to the highest activity amonga ll the samples, in which methanec ould be initially ignited below 200 8C and completely converted to CO 2 at 375 8C. This activity is attributed to the collective contribution from all the exposed high-index planes of 2D Co 3 O 4 andt om ore surface-active species being formed on 2D Co 3 O 4 .Natural gas is widely used in power generation,c hemicals, and vehicle fuels. The main component of natural gas,m ethane, is as ymmetrical molecule and av ery stable hydrocarbon.[1] Most methanec onversions are thermodynamically unfavorable at low temperatures owing to the positivea nd large value of the Gibbs free energy;t hus, ah igh reactiont emperature is generally required. The removal of methane from the environmenti s highly challenging for catalyst suppliers, as the high-temperature combustion leads to undesirable surface reactions and the emission of toxic nitrogen oxides (NO x )a nd CO.[2] Therefore, the developmento fa ctive catalysts forl ow-temperature methane combustion is crucial to remove methane from the environment and limit the emission of toxic gases.A lthough Pd is the best known methane combustion catalyst, [3] owing to the high cost of Pd and declining activity,a lternative catalysts based on non-noblem etals or metal oxides are being actively pursued. Many efforts have been made to obtain perovskite oxides, [4] hexaaluminates, [5] and transition metal oxides [2,6] for methane combustion at low temperature. Co 3 O 4 is one of the most intensively investigated transition metal oxides owing to its excellent performance in various catalytic processes, for example,C Oo xidation, [7] NO x reduction, [8] and the oxygen reduction reaction( ORR).[9] The properties of as-synthesized Co 3 O 4 mainlyd epend on its shape, surface structure, crystal phase, crystal size, and dimensionality.I th as been reported that, in the catalytic combustion of methane,C o 3 O 4 nanosheets enclosed by {112}p lanes exhibit highera ctivity than the corresponding nanobelts with exposed (0 11)f acets or nanocubes with exposed (0 01)f acets.[10] Co 3 O 4 nanotubes bounded by {112}p laness how excellent activity and good stability compared with Co 3 O 4 nanorods with exposed (110)f acets.[11] So far,however,Co 3 O 4 as aheterogeneous catalystwith controlled dimensionality hasr arely been mentioned in this catalytic reaction.In this work, to determine the spatial structuree ffect of Co 3 O 4 on methanec ombustion, we set out to synthesize Co 3 O 4 catalysts with fascinating architectures from 0D (dimensional) to 3D,s uch as nanoparticles (0 D), nanorods (1 D), ...

Integral structured Co–Mn composite oxides grown on interconnected Ni foam for catalytic toluene oxidation

“…6a), the peaks at the binding energy of 779.9, 781.5 and 785.5 eV are related to surface Co 3+ , Co 2+ and satellite peak of Co species, respectively. 17,18,31 In addition, the Mn 2p 3/2 XPS spectrum in Fig. 6b , represents an oxygen vacancy in the catalysts.…”

“…Various transition metal oxides as active components in reaction processes have been extensively studied to replace noble metals over the past several years, because they have low cost, unique structural morphology, adequate catalytic activity and high thermal stability. 3,[17][18][19][20][21] Co 3 O 4 , a transition metal oxide, has been proven to excellent catalytic activity in numerous reactions duo to its superior physical-chemical properties. [22][23][24][25][26][27] Additionally, extensive efforts have revealed that the synergistic effect of Co species and other transition metal oxides has dramatically enhanced the redox properties and catalytic activities due to the formation of a solid solution, compared with single oxides.…”

Effect of Preparation Method of Co-Ce Catalysts on CH4 Combustion

“…As suggested in several studies, during methane combustion the lattice oxygen in the oxide surface contributes to the oxidation of CH x , thus leading to the formation of an oxygen vacancy, available for oxygen adsorption from the gas-phase. Both the adsorbed oxygen, as well as the surface lattice oxygen, are considered crucial for oxidation reactions, as they contribute to the adsorption/activation of oxygen and, thus, the desired oxidation of intermediates on the catalyst surface [11,32,33]. Oxygen-temperature programmed desorption (O 2 -TPD) experiments have evidenced that oxygen molecules were released from Co 3 O 4 nanomaterials, suggesting that these oxygen molecules were adsorbed on the surface oxygen vacancies of the oxides [32].…”

Bowtie‐Shaped NiCo2O4 Catalysts for Low‐Temperature Methane Combustion

“…Among these, Co 3 O 4 exhibits good activity for methane combustion attributed to a spinel‐type structure with variable Co oxidation states and a high density of oxygen vacancies on the surface . Additionally, the specific exposed facets and morphology of Co 3 O 4 plays an important role in the catalysis . Materials with exposed (110) planes show enhanced catalytic activity for methane oxidation compared with those only exposing (100) or (111) facets, enabling complete methane conversion below 400 °C (GHSV = 40 000 mL g −1 h −1 ) .…”