In Situ Surface-Enhanced Raman Spectroscopy Study of the Electrocatalytic Effect of PtFe/C Nanocatalyst on Ethanol Electro-Oxidation in Alkaline Medium

Abstract

Currently, the ethanol electro-oxidation reaction has attracted considerable attention in fuel cells because of new green ethanol synthetic methods based on biomass processes that have emerged. In this study, PtFe/C and Pt/C nanoparticles were synthesized by a chemical reduction method and tested in the ethanol electro-oxidation reaction. Furthermore, the electrocatalytic effect of the PtFe bimetallic catalyst was analyzed by in situ surface-enhanced Raman spectroscopy (SERS) coupled to an electrochemical cell. X-ray diffractograms showed typical face-centered cubic structures with crystallite sizes of 3.31 and 3.94 for Pt/C and PtFe/C, respectively. TEM micrographs revealed nanoparticle sizes of 2 ± 0.4 nm and 3 ± 0.6 nm for Pt/C and PtFe/C respectively. PtFe/C exhibited a Pt 90 Fe 10 composition by both X-ray fluorescence and energy-dispersive X-ray spectroscopy. A better electrocatalytic activity as function of concentration was obtained through the incorporation of a small amount of Fe into the Pt lattice and the presence of Fe 2+ /Fe 3+ (observed by X-ray photoelectron spectroscopy). According to SERS experiments, the presence of these iron species promotes the chemisorption of ethanol, the formation of formic acid as main product and renewal of the catalytic sites, resulting in current densities that were at least three fold higher than the values obtained for the Pt/C nanocatalyst.

The Role of Metal–Organic Frameworks in Moderating Platinum-Based Ethanol Electrooxidation Catalysts

“…Three bands between 2890 and 2980 cm –1 are characteristic valence vibrations of the CH 3 and CH 2 groups. The following signals can also be assigned to ethanol: δ­(C–O–H) at 1460 cm –1 , ν­(C–O–H) at 1094 cm –1 , ν a (C–C–O) at 1056 cm –1 and ν s (C–C–O) at 890 cm –1 . A “tailing” of the D1 band at about 1282 cm –1 is found in the ZIF-8-modified sample.…”

“…There are no characteristic vibrations due to ZIF-8 detectable for two reasons: (i) The most intense signals of ZIF-8 are expected in the range of 1000 to 1500 cm −1 , that is, they are superimposed by the intense bands of the carbon material. 46 47 A "tailing" of the D1 band at about 1282 cm −1 is found in the ZIF-8-modified sample. The latter signal can be explained by the δ(COH) and t(CH 2 ) vibrations of ethanol.…”

Hybrid palladium nanoparticles and nickel single atom catalysts for efficient electrocatalytic ethanol oxidation

“…During the electrochemical tests, several new peaks were observed at a potential as low as 0.04 V. For the products of the EOR, the bands located at 740, 762, 790, and 840 cm −1 were attributed to the C–H vibrations of acetaldehyde, while the peak at 925 cm −1 was assigned to the CH 3 band of acetic acid. 35 Moreover, the peaks at 875 and 1454 cm −1 were assigned to the characteristic ν s(C–C–O) and δ (C–O–H) bands of ethanol. 36 The ν a(C–C–O) and γ (C–O–H) bands were also found at 1048 and 1090 cm −1 .…”

Ethanol Electrooxidation on an Island-Like Nanoporous Gold/Palladium Electrocatalyst in Alkaline Media: Electrocatalytic Properties and an In Situ Surface-Enhanced Raman Spectroscopy Study

“…The two bands at 770 and 1190 cm −1 were assigned as the C− H wagging and C−O−H stretch [ν(C−O−H)] vibrations of acetaldehyde. 25 The Raman band at 960 cm −1 was assigned as the CH 3 rocking of acetic acid. Besides, the vibration band ν(C�O) related to the carbonyl of acetaldehyde was found at 1785 cm −1 .…”

“…Besides, SERS has a larger frequency range than FTIR, which provides possible analysis of the vibrational spectra at metal–solution interfaces at low wavenumber. Several works have been reported to monitor the EOR via SERS, but their SERS performance may be limited by the inadvertent microstructures, leading to the inability to stimulate Raman signals of more products. , Therefore, it is necessary to create a catalyst with a better SERS performance to capture the SERS signal of trace molecules, so as to better monitor the EOR process. NPG, fabricated by the dealloying of a gold (Au)-based alloy, is considered to be an excellent SERS substrate because of its high Raman enhancement effect, homogeneity, and stability. , Thus, the combination of NPG and Pd nanoparticles can be used not only as a catalyst to further improve the catalytic performance of EOR but also as a SERS substrate to monitor the EOR process.…”