Kinetics of Toluene Electrohydrogenation on Pt/C Catalyst

International audienceThe kinetics of the toluene (TL) electrohydrogenation on a carbon-supported platinum catalyst (Pt/C) have been investigated as a fundamental study of the cathode reaction in an electrolyzer with water decomposition. Since the TL electrohydrogenation on a Pt wire and Pt/C catalyst is a fast kinetic reaction with a low solubility, and slow mass transfer in an aqueous electrolyte, a potential step sequence was employed to determine its kinetic performance. Based on this method, a non-faradic current and faradic current could be identified and thereafter separated by a capacitance simulation. This experiment was performed in a TL-saturated sulfuric acid electrolyte to minimize the effect of the TL mass transfer. Based on the mass transfer-free TL electrohydrogenation experimental results, the exchange current densities of the TL electrohydrogenation on the Pt/C were 0.48, 0.49, 0.72, and 0.8mAcm(-2) at 25, 40, 50, and 60 degrees C, respectively. We found that the carbon support has a high impact towards the TL electrohydrogenation on the Pt-supported material. The carbon material works as a sponge by absorbing TL from the solution, and providing a large TL coverage for the Pt surface. Finally, a Tafel plot of the TL electrohydrogenation on the Pt/C catalyst was obtained and the kinetic performance was determined. The apparent active energy of the TL electrohydrogenation on the Pt/C was then calculated as 13.1kJmol(-1)

A New Accelerated Durability Test Protocol for Water Oxidation Electrocatalysts of Renewable Energy Powered Alkaline Water Electrolyzers

For electrocatalysts of oxygen evolution reaction (OER), a new accelerated durability test (ADT) protocol is presented. The protocol is designed to closely mimic the fluctuations of renewable energies. The unit cycle of the current ADT protocol represents the “ON/OFF” operation mode. In the “ON” step, the electrolyzer operates under a DC current of 0.6 A cm−2. In the “OFF” step, the electrocatalyst is subjected to a constant potential that is clearly more cathodic than its OER onset potential (namely, 0.3, 0.5, and 0.7 V vs. RHE) for 10 or 60 s. The transition from the “ON” state to the “OFF” state occurs through a cathodic linear sweep voltammetry of a fast sweep rate to mimic the sudden changes in the renewable power. A NiCoOx/Ni-mesh electrode was used as a case study. The electrode showed remarkable durability under continuous operation (i = 0.6 A cm−2) for about 900 hours. However, it did suffer severe degradation after a certain number of ADT cycles, and the rate of degradation mainly depends on the potential value and the duration of the “OFF” step. Interestingly, the inclusion of the 10-sec open-circuit potential step after the “ON” step clearly mitigates the impact of energy fluctuations on the durability of OER electrocatalysts

Emotional Contagion From Humans to Dogs Is Facilitated by Duration of Ownership

Emotional contagion is a primitive form of empathy that does not need higher psychological functions. Recent studies reported that emotional contagion exists not only between humans but also among various animal species. The dog (Canis familiaris) is a unique animal and the oldest domesticated species. Dogs have coexisted with humans for more than 30, 000 years and are woven into human society as partners bonding with humans. Dogs have acquired human-like communication skills and, likely as a result of the domestication process, the ability to read human emotions; therefore, it is feasible that there may be emotional contagion between human and dogs. However, the higher time-resolution of measurement of emotional contagion between them is yet to be conducted. We assessed the emotional reactions of dogs and humans by heart rate variability (HRV), which reflects emotion, under a psychological stress condition on the owners. The correlation coefficients of heart beat (R-R) intervals (RRI), the standard deviations of all RR intervals (SDNN), and the square root of the mean of the sum of the square of differences between adjacent RR intervals (RMSSD) between dogs and owners were positively correlated with the duration of dog ownership. Dogs’ sex also influenced the correlation coefficients of the RRI, SDNN, and RMSSD in the control condition; female showed stronger values. These results suggest that emotional contagion from owner to dog can occur especially in females and the time sharing the same environment is the key factor in inducing the efficacy of emotional contagion

Optimisation of the Solid Oxide Fuel Cell (SOFC) cathode material Ca₃Co₄O_9-δ

This paper focuses on the electrochemical potentialities of the 2D misfit compound Ca3Co4O9-delta, so far mainly investigated for its thermoelectric properties. Its expansion coefficient (TEC = (9-10) x 10(-6)degrees C-1) and its chemical stability are compatible with standard CGO IT-electrolyte and the first optimisation steps of the deposited cathode have been performed with the aim to minimise the ASR and increase the cell durability. Particular attention has been paid on the effect of thickness and microstructure for pure and composite cathodes. The electrode reaction was performed on symmetrical cells. The preliminary results presented here show that the composite (70 wt.% Ca3Co4O9-delta-30 wt.% CGO) gives the lowest ASR values compare to single-phased electrodes. Strikingly, the ASR values increase for thinner deposited layers. The effect of various current collectors (gold grid vs. platinum paste) has been also checked. (C) 2011 Elsevier B.V. All rights reserved.</p

Testosterone Increases the Emission of Ultrasonic Vocalizations With Different Acoustic Characteristics in Mice

International audienceTestosterone masculinizes male sexual behavior through an organizational and activational effects. We previously reported that the emission of ultrasonic vocalizations (USVs) in male mice was dependent on the organizational effects of testosterone; females treated with testosterone in the perinatal and peripubertal periods, but not in adults, had increased USV emissions compared to males. Recently, it was revealed that male USVs have various acoustic characteristics and these variations were related to behavioral interactions with other mice. In this regard, the detailed acoustic characteristic changes induced by testosterone have not been fully elucidated. Here, we revealed that testosterone administered to female and male mice modulated the acoustic characteristics of USVs. There was no clear difference in acoustic characteristics between males and females. Call frequencies were higher in testosterone propionate (TP)-treated males and females compared to control males and females. When the calls were classified into nine types, there was also no distinctive difference between males and females, but TP increased the number of calls with a high frequency, and decreased the number of calls with a low frequency and short duration. The transition analysis by call type revealed that even though there was no statistically significant difference, TP-treated males and females had a similar pattern of transition to control males and females, respectively. Collectively, these results suggest that testosterone treatment can enhance the emission of USVs both in male and female, but the acoustic characteristics of TP-treated females were not the same as those of intact males

Rate Enhancements in Structural Transformations of Pt–Co and Pt–Ni Bimetallic Cathode Catalysts in Polymer Electrolyte Fuel Cells Studied by in Situ Time-Resolved X‑ray Absorption Fine Structure

In situ time-resolved X-ray absorption fine structure spectra of Pt/C, Pt₃Co/C, and Pt₃Ni/C cathode electrocatalysts in membrane electrode assemblies (catalyst loading: 0.5 mg_metal cm^–2) were successfully measured every 100 ms for a voltage cycling process between 0.4 and 1.0 V. Systematic analysis of in situ time-resolved X-ray absorption near-edge structure and extended X-ray absorption fine structure spectra in the molecular scale revealed the structural kinetics of the Pt and Pt₃M (M = Co, Ni) bimetallic cathode catalysts under polymer electrolyte fuel cell operating conditions, and the rate constants of Pt charging, Pt–O bond formation/breaking, and Pt–Pt bond breaking/re-formation relevant to the fuel cell performances were successfully determined. The addition of the 3d transition metals to Pt reduced the Pt oxidation state and significantly enhanced the reaction rates of Pt discharging, Pt–O bond breaking, and Pt–Pt bond re-forming in the reductive process from 1.0 to 0.4 V