Sulaiman N N, Mustafa N S, Ismail M
School of Ocean Engineering, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Malaysia.
Dalton Trans. 2016 Apr 28;45(16):7085-93. doi: 10.1039/c6dt00068a.
The effects of Na3FeF6 catalyst on the hydrogen storage properties of MgH2 have been studied for the first time. The results showed that for the MgH2 sample doped with 10 wt% Na3FeF6, the onset dehydrogenation temperature decreased to 255 °C, which was 100 °C and 162 °C lower than those of the as-milled and as-received MgH2 sample, respectively. The re/dehydrogenation kinetics were also significantly enhanced compared to the un-doped MgH2. The absorption kinetics showed that the as-milled MgH2 only absorbed 3.0 wt% of hydrogen at 320 °C in 2 min of rehydrogenation, but about 3.6 wt% of hydrogen was absorbed within the same period of time after 10 wt% Na3FeF6 was added to MgH2. The desorption kinetics showed that the MgH2 + 10 wt% Na3FeF6 sample could desorb about 3.8 wt% of hydrogen in 10 min at 320 °C. In contrast, the un-doped MgH2 sample desorbed only 0.2 wt% of hydrogen in the same period of time. The activation energy for the decomposition of the as-milled MgH2 was 167.0 kJ mol(-1), and this value decreased to 75.0 kJ mol(-1) after the addition of 10 wt% Na3FeF6 (a reduction by about 92.0 kJ mol(-1)). It is believed that the in situ formation of the active species of NaMgF3, NaF and Fe during the heating process could enhance the hydrogen storage properties of MgH2, due to the catalytic effects of these new species.
首次研究了Na3FeF6催化剂对MgH2储氢性能的影响。结果表明，对于掺杂10 wt% Na3FeF6的MgH2样品，起始脱氢温度降至255℃，分别比球磨态和原样MgH2样品低100℃和162℃。与未掺杂的MgH2相比，其吸/脱氢动力学也显著增强。吸收动力学表明，球磨态MgH2在320℃再氢化2分钟内仅吸收3.0 wt%的氢，但在MgH2中添加10 wt% Na3FeF6后，在相同时间内吸收了约3.6 wt%的氢。解吸动力学表明，MgH2 + 10 wt% Na3FeF6样品在320℃下10分钟内可解吸约3.8 wt%的氢。相比之下，未掺杂的MgH2样品在相同时间内仅解吸0.2 wt%的氢。球磨态MgH2分解的活化能为167.0 kJ mol(-1)，添加10 wt% Na3FeF6后该值降至75.0 kJ mol(-1)(降低了约92.0 kJ mol(-1))。据信，加热过程中原位形成的活性物种NaMgF3、NaF和Fe由于这些新物种的催化作用，可增强MgH2的储氢性能。
