Electronic Metal–Support Interactions between Pt Nanoparticles and Co(OH)₂ Flakes for CO Oxidation

Abstract

Electronic metal–support interactions (EMSIs) have opened a new way to tailor the electronic and catalytic properties of supported catalysts. Herein, we demonstrate the EMSIs between Pt nanoparticles and Co­(OH)2 flakes grown on SiO2 and show its beneficial effect on enhancing the CO oxidation activity. The EMSI characteristics of the Pt–Co­(OH)2/SiO2 catalyst are identified by in situ X-ray absorption fine structure (XAFS) spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and transmission electron microscopy. Quantitative XAFS analysis reveals the presence of metallic-like Pt–Co bonds. The formation of Pt–Co intermetallic bonds allows for electron donation form Co to Pt, leading to the negative charging of the Pt atoms as evidenced by reduced Pt 2p-to-5d electron-transition intensity detected by XAFS spectroscopy and the emergence of a CO adsorption band at 2063 cm–1 in DRIFTS. The significance of EMSIs is manifested by comparing the CO oxidation activity over the Pt–Co­(OH)2/SiO2 and Pt/SiO2 catalysts with similar Pt loadings. Pt–Co­(OH)2/SiO2 is superior to Pt/SiO2 in both the apparent activation energy (19 vs 64 kJ/mol) and the turnover frequency (0.03 vs 0.003 s–1 at 37 °C). The enhanced activity is attributed to the negative charging of Pt, which downshifts the d-band center and reduces the CO adsorption strength.

Three-Dimensional Porous Nitrogen-Doped Carbon Nanosheet with Embedded NixCo3–xS4 Nanocrystals for Advanced Lithium–Sulfur Batteries

“…X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (XAFS) spectra exhibit similar spectral features to those of the bulk Co­(OH) 2 , further confirming the atomic structure of the obtained NiCo–LDH+2MIM hybrid (Figure S6). , …”

“…X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (XAFS) spectra exhibit similar spectral features to those of the bulk Co(OH) 2 , further confirming the atomic structure of the obtained NiCo− LDH+2MIM hybrid (Figure S6). 30,31 The as-prepared NiCo−LDH+2MIM precursor with a Ni/ Co ratio of 1:1.3 was annealed (500 °C) in a sulfur atmosphere under Ar flow. After the annealing process, the 2-MIM molecules in the precursor in situ transform into the pyrolytic nitrogen-doped carbon materials.…”

The mechanism of Co oxyhydroxide nano-islands deposited on a Pt surface to promote the oxygen reduction reaction at the cathode of fuel cells

“…Then, Pt-OCoOH was successfully prepared by the precipitation and impregnation of nano Pt particles with urea (DPU) as the sustained release agent. 31 The preparation procedure is described below.…”

“…The more electrons Pt contributes, the more stable the bridged oxygen bond. 31 Due to the introduction of the -OCoOH group, the electron cloud density on the surface of the adjacent Pt decreases (transfer 0.4e to -OCoOH). The predicted density of state (PDOS) of Pt-OCoOH (Fig.…”

Identification of Active Sites in Pt–Co Bimetallic Catalysts for CO Oxidation

“…Numerous strategies have been developed to promote the low-temperature activity and stability of PGM catalysts. Among them, alloying with a second transition metal is an effective way because it can induce electron transfer and strain effects between the two metals, thus modifying the surface electronic structures of PGMs and altering the CO-binding strength. − Another strategy is to decorate the surface of PGM nanocatalysts with transition-metal oxide to form a metal-oxide interface. ,− The decorated oxides may act as active sites for O 2 activation or help tailor the electronic and chemical states of metal catalysts. Nevertheless, there are still long-term debates regarding the nature of real active sites (alloy vs metal-oxide interfaces).…”