Structure Evolution of Co–CoO_x Interface for Higher Alcohol Synthesis from Syngas over Co/CeO₂ Catalysts

Abstract

CeO 2 nanorods supported Co−CoO x catalysts showed high selectivity for higher alcohol synthesis (HAS) from syngas. The selectivity has found to increase with lowering the Co loadings, and the value over Co 1 /CeO 2 (19.86%) is twice higher than that over Co 5 /CeO 2 (8.67%).The active sites at the interfaces between Co 0 and CoO x , or to say, Co−CoO x pairs, have evidenced to be responsible for HAS. The strong metal−support interactions between Co and CeO 2 retard the reduction of CoO x and stabilize the intermediates such as CO−Co δ+ . Likely, CO favors dissociating on the metallic Co surface to form CH x species, while CO is associatively activated on Co δ+ sites. Moreover, the structure evolution of the Co−CoO x interface was revealed during calcination, reduction, and reaction using in situ X-ray diffraction (XRD), in situ Raman spectroscopy, X-ray absorption spectroscopy (XAS), and in situ diffuse reflectance infrared fourier transform spectroscopy (CO-DRIFTS). The structure−performance relationship of HAS over Co/CeO 2 was proposed.

A Phthalocyanine‐Based Layered Two‐Dimensional Conjugated Metal–Organic Framework as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction

“…Due to the electronic transition from 1s to 4p,astrong absorption peak (white line) appears,w hich is at ypical feature of Co atoms with different Co-O environments and oxidation states. [40,41] In addition, the absorption peak of the white line of PcCu-O 8 -Co is located before that of Co 3 O 4 and close to that of CoO, indicating the oxidation valence of Co atom as + 2, which is consistent with the XPS results. [40,41] In addition, the absorption peak of the white line of PcCu-O 8 -Co is located before that of Co 3 O 4 and close to that of CoO, indicating the oxidation valence of Co atom as + 2, which is consistent with the XPS results.…”

“…[40,42] PcCu-O 8 -Co,C oO,a nd Co 3 O 4 show strong white line absorption intensities,while Co foil exhibits av ery weak white line feature (Figure 2b). [40,41] In addition, the absorption peak of the white line of PcCu-O 8 -Co is located before that of Co 3 O 4 and close to that of CoO, indicating the oxidation valence of Co atom as + 2, which is consistent with the XPS results.…”

“…[29,30] Thec hemical states of Co and Cu atoms in PcCu-O 8 -Co were further determined by X-ray absorption near-edge structure (XANES) analysis (Figure 2a). [39][40][41] Cu K-edge spectra of PcCu-O 8 -Co and the monomer {PcCu-(OH) 8 }a re similar and resemble that of the reference compound copper-(II) phthalocyanine (PcCu) since they all have the same common Cu-N motif.These spectra are distinctly different to those of Cu foil and CuO,c onfirming the CuÀNb onding in PcCu-O 8 -Co.I nt he Co K-edge spectra, the pre-edge at 7709 eV originates from the absorption transition from 1s to 3d. Due to the electronic transition from 1s to 4p,astrong absorption peak (white line) appears,w hich is at ypical feature of Co atoms with different Co-O environments and oxidation states.…”

A Phthalocyanine‐Based Layered Two‐Dimensional Conjugated Metal–Organic Framework as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction

“…Due to the electronic transition from 1s to 4p, a strong absorption peak (white line) appears, which is a typical feature of Co atoms with different Co‐O environments and oxidation states . PcCu‐O 8 ‐Co, CoO, and Co 3 O 4 show strong white line absorption intensities, while Co foil exhibits a very weak white line feature (Figure b) . In addition, the absorption peak of the white line of PcCu‐O 8 ‐Co is located before that of Co 3 O 4 and close to that of CoO, indicating the oxidation valence of Co atom as +2, which is consistent with the XPS results.…”

“…The chemical states of Co and Cu atoms in PcCu‐O 8 ‐Co were further determined by X‐ray absorption near‐edge structure (XANES) analysis (Figure a) . Cu K‐edge spectra of PcCu‐O 8 ‐Co and the monomer {PcCu‐(OH) 8 } are similar and resemble that of the reference compound copper(II) phthalocyanine (PcCu) since they all have the same common Cu‐N motif.…”