| 1. |
- Jensen, Emil H., et al.
(författare)
-
The Effect of Y Content on Structural and Sorption Properties of A2B7-Type Phase in the La–Y–Ni–Al–Mn System
- 2023
-
Ingår i: Molecules. - 1431-5157 .- 1420-3049. ; 28:9
-
Tidskriftsartikel (refereegranskat)abstract
- Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.
|
|
| 2. |
- Salvi, Paolo, et al.
(författare)
-
Hydrogen evolution reaction in PTFE bonded Raney-Ni electrodes
- 2011
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 36:13, s. 7816-7821
-
Tidskriftsartikel (refereegranskat)abstract
- This study is concerned with the hydrogen evolution reaction (HER) in several PTFE bonded Raney-Ni electrodes as function of temperature and treatments. The Mo-doped Raney-Ni catalysts are activated by hours of long cathodic polarization interleaved with few deep "charge - discharge" (polarity reversal) cycles. Moreover, the HER efficiency of the electrode requires additives which enhance conductivity and surface properties: with powders of Ni alloys (Ni-Ti, Ni-Cr, Ni-Fe) the electrode becomes also more stable, and almost insensitive to polarity reversal. The main effect of a temperature increase is the reduction of the Tafel slope, which is about 120 mV/dec at 25 degrees C, and about 60 mV/dec at 60 degrees C. A proper choice of additives yield electrodes which withstand polarity reversal and may be used in electrolysers which are intermittently operated, or have anodes which require periodic in situ re-activation by reduction.
|
|
