High‐Performance Ultrathin Co₃O₄ Nanosheet Supported PdO/CeO₂ Catalysts for Methane Combustion

Abstract

As one of the most important noble metals, Pd species including Pd 0 and PdO x based catalysts have exhibited excellent catalytic activity toward methane combustion at relatively low temperatures. [2,3] During manufacturing applications the active Pd species were usually loaded on metal oxides (MO x ) supports via the traditional deposition precipitation [4,5] or impregnation [6,7] methods in which good Pd dispersion could result in ideal initial catalytic activity. However, these strategies brought an obvious drawback that the as-obtained Pd nanocatalysts with overexposed active centers often exhibited unsatisfied thermal stability caused by sintering. To solve this problem, kinds of Pd@MO x core(yolk)@shell nanostructures [8][9][10] and Pd-metal alloys [11][12][13] have been successfully investigated to improve anti-sintering ability of Pd despite the catalytic active centers might be partially blocked, so it seems hard to reconcile activity and stability. Moreover, most of the Pd@MO x core@shell nanostructures and Pd-metal alloys are prepared by toxic and complex organic routes that limit mass production for application.From a widely accepted viewpoint of catalysts design, there should be enough exposed active centers and highly dispersed Pd species as catalytic sites, strong coupling between Pd and MO x to produce effective synergistic effects, [14,15] and welldefined MO x nanostructures as supports to get large specific surface areas and rational pore distributions. [16][17][18][19][20] Obviously, the properties of MO x supports greatly determined the final performance of Pd catalysts. [21,22] 2D nanosheets (NSs) have been considered as good supports to anchor Pd, which are of large aspect ratios and high specific surface areas. [23][24][25] Such 2D material supported hybrid nanocatalysts have been successfully used in photocatalysis [26] and electocatalysis, [27,28] showing potential applications for renewable energy production and environment remediation. [29,30] However here comes a new question that these reported ultrathin 2D NSs are mainly based on carbon materials, [31,32] metal chalcogenide, [33] and transition metal hydroxides [34,35] that are hard to survive from calcination caused by thermal decomposition and meanwhile transformed into oxides. As a result, the initial 2D nanostructures were thoroughly damaged into heavily aggregated nanoparticles (NPs), leading to bad catalytic performance during heterogeneous catalysts.For years we have been focusing on preparation of noble metal or MO x catalysts with well-defined nanostructures via nonorganic routes, especially for those CeO 2 encapsulated ones. [36][37][38][39][40] CeO 2 is of excellent oxygen storage/release capacity, Efficient utilization of methane via catalytic complete combustion is a very important pathway to realize energy efficiency and pollution reduction. From the viewpoint of structural design, herein a green water-phase route is developed to prepare ultrathin Co(OH) 2 nanosheet supported Pd catalysts. As a platform, the as-obtained...

Encapsulation of Co3O4 Nanocone Arrays via Ultrathin NiO for Superior Performance Asymmetric Supercapacitors

“…The results well correlate with the previous reports. [ 38,40,41 ] Figure 1e shows multiple peaks with spin–orbit doublets corresponding to Ni 2p 3/2 and Ni 2p 1/2 components in Ni 2p. The binding energy peaks at 854.29 and 871.88 eV attributes to the Ni 2+ state and 856.00 and 874.33 eV attributes to Ni 3+ state in Ni 2p doublets.…”

“…The results well correlate with the previous reports. [38,40,41] Figure 1e shows multiple peaks with spin-orbit doublets corresponding to Ni 2p 3 [42,43] XPS spectrum of O 1s shows three distinct deconvoluted peaks as shown in Figure 1f. The binding energy peak at 529.73 eV corresponds to the bonding between metal-oxygen (CoO or NiO in the present case), whereas the peaks centered at 530.97 and 532.34 eV can correspond to the oxygen molecules chemisorbed on the sample as surface hydroxyls.…”

Penta‐coordinated Al3+ Stabilized Defect‐Rich Ceria on Al2O3 Supported Palladium Catalysts for Lean Methane Oxidation

“…Li et al. reported that the combination of Pd species and hybrid oxide centers in the Co 3 O 4 −CeO 2 interface affords a positive reaction pathway for the catalytic lean methane combustion [12] . Moreover, the Pt‐SAs stabilized at the CeO x −TiO 2 hybrid interfaces was reported to be more active toward CO oxidation via activating the interface‐mediated MvK mechanism and facilitating its catalytic performance against CO‐poisoning [13] .…”

“…It is widely recognized that the formation of reduced Ce 3+ species is associated with the generation of oxygen defect sites due to a charge compensation [27] . According to the previous literatures, [12,28] the surface Ce 3+ concentration is identified by the total peak area of S1 (v ′ + u ′ ), and the amount of Ce 4+ is calculated by S2 (v 0 +v ′′ +v ′′′ +u 0 +u ′′ +u ′′′ ). As showed in Ce 3d XPS spectra (Figure 6), the ratio of Ce 3+ can be determined by the relation of S1/(S1+S2).…”

Controlled Synthesis of Porous Co3O4 Nanostructures for Efficient Electrochemical Sensing of Glucose

“…However, the inherently high electronic resistance and low surface area of Co 3 O 4 retard its practical application [12]. Generally, the electrocatalytic properties of materials are strongly dependent on their morphology and microstructures, which creates substantial differences in the surface area, particle size, pore structure, mass transport, and electron transfer efficiency, which in turn influence their electrochemical sensing performance [13]. Therefore, the morphology and nanostructure control of Co 3 O 4 are of vital importance to improve the electrochemical reactivity [6].…”