In-situ FTIR

Yu Li2012.09.05

Effect of Particle Size and Composition on CO-Tolerance at Pt−Ru/C Catalysts Analyzed by In Situ Attenuated Total Reflection FTIR Spectroscopy

Takako Sato,† Kazuki Okaya,† Keiji Kunimatsu,‡ Hiroshi Yano,‡ Masahiro Watanabe,*,‡and Hiroyuki Uchida*,‡,§dx.doi.org/10.1021/cs200550t | ACS Catal. 2012, 2, 450−455

Introduction

The particle size dependence of activities for the hydrogen oxidation

reaction(HOR) on monodisperse Pt2Ru3 (d = 2.6, 3.6, and 4.5 nm)

supported on carbon black prepared by the nanocapsule method was

investigated by in situ attenuated total reflection Fourier-transform infrared

(ATR-FTIR) spectroscopy.

The effect of chemical composition on the CO-tolerance was also

analyzed on Pt2Ru3/C and PtRu/C with the identical particle size d = 2.6nm

at 25 and 60 ℃.

Particle Size Dependencies

Changes in ( ) I[COL], (○) I[COB], (▲) I[CO−Ru], and▽(solid black lines) HOR mass activity

Changes in FTIR spectra of Pt2Ru3/C electrodesat 25°C (dashed line) and 60 °C (solid line)

Particle Size Dependencies

Particle size dependencies of (a) CO-tolerance parameterMA(θCO≈0.9)/MA(θCO = 0)

The values of MA(θCO≈0.9)/MA(θCO = 0) increased in the order, 4.5 nm < 3.6 nm < 2.6 nm at both temperatures (25 and 60 °C). The highest CO-tolerant HORactivity at both temperatures was observed for the smallest Pt2Ru3 particle (d = 2.6 nm) with a Pt-rich top surface and Ru richcore.

Alloy Composition on CO-Tolerance

Comparison of FTIR spectra of PtRu/C (solid line) andPt2Ru3/C (dotted line) electrodes observed at 0.02 V in 1% CO (H2balance)-saturated 0.1 M HClO4 solution at (a) 25

and (b) 60 after 120 min of CO adsorption. The ℃ ℃spectra were normalized withrespect to the value of I[COL].

The I[CO−Ru] on PtRu/C was smaller than that on Pt2Ru3/C, whereas I[COB] on PtRu/C was larger than that on Pt2Ru3/C.Owning to the lower θ[COB], probably because of an electronic effect of the Ru-rich core Pt2Ru3/C showed higher CO-tolerance. The suppression of COB is essential to maintain active Pt−Pt pair sites for the HOR, as well as the increase in the mobility of COad by the electronic modification effect of Ru, as discussed in the previous section.

Ethanol oxidation on PtRuMo/C catalysts: In situ FTIR spectroscopy and DEMS studies

Gonzalo Garcı´a a,b, Nikolaos Tsiouvaras a, Elena Pastor b, Miguel A. Pen˜a a,Jose Luis G. Fierro a, Marı´a V. Martı´nez-Huerta a,*Hydrogen Energy Publications doi:10.1016/j.ijhydene.2011.11.031

Introduction

The development of catalyst for direct ethanol fuel cells (DEFC) has gained a great interest. The electrooxidation of ethanol on carbon supported PtRuMo nanoparticles of different Mo compositions has been studied in the temperature range of 30-70 .℃ In situ spectroelectrochemical studies have been used to identity adsorbed reaction intermediates and products (in situ Fourier transform infrared spectroscopy, FTIR) and volatile reaction products (differential electrochemical mass spectrometry, DEMS).

Experimental

colloidal method incorporated to the carbon

support---PtRu (1:1)

impregnation methodPrecursor---(NH4)6Mo7O24·

4H2O

synthesis method a nominal metal loading of

PtRu of 30 wt% and a Mo load of 0, 1 and 3 wt%, denoted PR,

1MPR and3MPR

Characterization---TGA 、 XRD 、 TEM 、

XPSStudy---DEMS 、 FTIR

In situ FTIR measurements

In situ FTIR spectra recorded during ethanol electrooxidation on the PR, 1MPR and 3MPR catalysts in 0.1 M CH3CH2OHD0.5 HClO4

In situ FTIR measurements

CO (2029 cmL1), CO2 (2342 cmL1), CH3COOH(1280 cmL1), and CH3COOHDCH3COH (1720 and1400 cmL1) band intensities on the PR, 1MPR and 3MPR catalysts at different potentials.

It can be observed a decreaseand an increase of the COad and 1280 cm1 signal with the Mo content, respectively, while the other signals remain constantor decrease/increase in a similar way with the Mo amount. The higher CO tolerance of PtRuMo/C catalysts results to minimum or no CO poisoning of the Pt and Ru surfaces, in contrast to the PtRu/C catalyst ,which is rapidly blocked by CO.This behavior allows a fast “replenishment” of the active sites on ternary catalysts leading to the formation of acetaldehyde and especially acetic acid.

PtSnCe/C electrocatalysts for ethanol oxidation: DEFC and FTIR “in-situ” studies

R.F.B. De Souza a, L.S. Parreira a, J.C.M. Silva a, F.C. Simo˜es a, M.L. Calegaro b, M.J. Giz c,G.A. Camara c, A.O. Neto d, M.C. Santos a,*Hydrogen Energy Publications doi:10.1016/j.ijhydene.2011.05.016

Introduction

At moderate temperatures, pure platinum is not an effective anode catalyst for ethanol or methanol electro-oxidation because it is poisoned by strongly adsorbed intermediates. Adsorbed carbon monoxide (COads) is one of the main poisoning species under these conditions. Pt-based alloys contain a second or a third metal to enhance the electrocatalytic properties of platinum by overcoming the poisoning related to methanol or ethanol electro-oxidation intermediates. Binary materials based on Pt and Sn are reported in the literature as the most effective for ethanol oxidation. The synergic effect of ceria (used as support) and tin has been studied.

Experimental

modified polymeric precursor method---precursors : H2PtCl6

·6H2O 、 SnCl2·2H2O 、 CeCl3

Pt, Sn and Ce in mass ratios of 72:23:5,

68:22:10 and 64:21:15ultrasonic bath ， treated

in an N2 atmosphere

Physical characterization ：XRD 、 TEMPerformance :chronoamperometry 、 polarization/densitypower curves 、 FTIR

Electrocatalytic performance

A change in the lattice parametersdue to the incorporation of Sn and/or Ce atoms

power density curves

In situ FTIR experiments

In situ FTIR spectra taken at several potentials (indicated) in 0.1 M HClO4D2.0 M EtOH for (a) PtSnCe/C (68:22:10), (b)PtSnCe/C (64:21:15) and (c) PtSn/C (E-Tek).

In situ FTIR experiments

Acetaldehyde, acetic acid and CO2 band intensitiesas a function of the potential for (,) PtSnCe/C (68:22:10),

(C) PtSnCe/C (64:21:15) and (6) PtSn/C.

The production of CO2 starts earlier forPtSnCe/C (68:22:10) than for the other catalysts. PtSnCe/C (68:22:10) is the best catalyst among those investigated because it generated more CO2, and the levels of acetic acid production were similar to those observed for PtSnCe/C(64:21:15). CO2 is generated from CO, there is no superficial oxide to promote the oxidation of acetaldehyde. The persistence of CO blockage prevents new cycles of adsorption and oxidation. The coverage of CO is little, indicating that the surface is partially free for the adsorption of other species. PtSnCe/C (68:22:10) has the highest activity because of the weakening of the CO-surface interaction and the capability to produce superficial oxides to continue the oxidation process.