The potential （E）-dependent vibrational behavior of a saturated CO adlayer on Au-core Pd-shell nanoparticle film electrodes was investigated over a wide potential range, in acidic, neutral, and basic solutions, using in situ surface-enhanced Raman spectroscopy （SERS）. Over the whole of the examined potential region （-1.5 to 0.55 V vs. NHE）, the peak frequencies of both the C-OM and the Pd-COM band （here, M denotes the multiply-bonded configuration） displayed three distinct linear regions： dvc oM/dE decreased from -185-207 （from -1.5 to -1.2 V） to -83-84 cm-1/V （-1.2 to -0.15 V）, and then to 43 cm-1/V （-0.2 to 0.55 V）; on the other hand, dvpd coM/dE changed from -10 to -8 cm I/V （from -1.5 to -1.2 V） to ^-31 to -30 cm-1/V （-1.2 to -0.15 V）, and then to -15 cm-1/V （-0.2 to 0.55 V）. The simultaneously recorded cyclic voltammograms revealed that at E 〈 -1.2 V, a hydro- gen evolution reaction （HER） occurred. With the help of periodic density functional theory calcula- tions using two different （2 × 2）-3CO slab models with Pd（111）, the unusually high dvc-oM/dE and the small dVPd-CoM/dE in the HER region were explained as being due to the conversion of COad from bridge to hollow sites, which was induced by the co-adsorbed hydrogen atoms formed from dissociated water at negative potentials.
The mechanism and kinetics of electrocatalytic oxidation of formic acid at Pt electrodes is discussed in detail based on previous electrochemical in-situ ATR-FTIRS data [Langmuir 22, 10399 （2006）and Angewa. Chem. Int. Ed. 50, 1159 （2011）]. A kinetic model with formic acid adsorption （and probably the simultaneous C-H bond activation） as the rate determining step, which contributes to the majority of reaction current for formic acid oxi- dation, was proposed for the direct pathway. The model simulates well the IR spectroscopic results obtained under conditions where the poisoning effect of carbon monoxide （CO） is negligible and formic acid concentration is below 0.1 mol/L. The kinetic simulation predicts that in the direct pathway formic acid oxidation probably only needs one Pt atom as active site, formate is the site blocking species instead of being the active intermediate. We review in detail the conclusion that formate pathway （with either 1st or 2nd order reaction kinetics） is the direct pathway, possible origins for the discrepancies are pointed out.
The temperature dependence of hydrogen evolution reaction （HER） at a quasi-single crystalline gold electrode in both 0.1 mol/L HCl04 and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential （η） and temperature from 278-333 K. In 0.1 mol/L HClO4 the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy （Ea） for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HC104 and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea-37 kJ/mol （η=0.2 V） to 30 kJ/mol （η=0.35 V）. In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with U. The pre-exponential factor （A） in 0.1 mol/L HC104 is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HC104 A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with U. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO4 and that in 0.1 mol/L KOH are discussed.
Methanol oxidation reaction （MOR） at Pt and Pt electrode surface deposited with various amounts of Ru （denoted as PtxRuy, nominal coverage y is 0.17, 0.27, and 0.44 ML） in 0.1 mol/L HClO4＋0.5 mol/L MeOH has been studied under potentiostatic conditions by in situ FTIR spectroscopy in attenuated-total-reflection con guration and di erential electro-chemical mass spectrometry under controlled flow conditions. Results reveal that （i） CO is the only methanol-related adsorbate observed by IR spectroscopy at all the Pt and PtRu electrodes examined at potentials from 0.3 V to 0.6 V （vs. RHE）; （ii） at Pt0.56Ru0.44, two IR bands, one from CO adsorbed at Ru islands and the other from COL at Pt substrate are detected, while at other electrodes, only a single band for COL adsorbed at Pt is observed; （iii） MOR activity decreases in the order of Pt0.73Ru0.27〉Pt0.56Ru0.44〉Pt0.83Ru0.17〉Pt; （iv） at 0.5 V, MOR at Pt0.73Ru0.27 reaches a current e ciency of 50% for CO2 production, the turn-over frequency from CH3OH to CO2 is ca. 0.1 molecule/（site sec）. Suggestions for further improving of PtRu catalysts for MOR are provided.
