碳载钯的添加对镁基储氢合金吸放氢性能的影响

Effects of multi-wall carbon nanotubes supported palladium addition on hydrogen storage properties of magnesium hydride

采用溶液化学还原法制备钯载量分别为10%、20%、30%和40%(质量分数)的多壁碳纳米管载钯(Pd/MWCNTs)催化剂,然后与Mg粉混合成95Mg-m Pd/(5-m)MWCNTs(m=0.5、1、1.5和2),采用氢化燃烧合成法(HCS)制备镁基氢化物,最后机械球磨(MM)10 h。采用X线衍射(XRD)、透射电子显微镜(TEM)、场发射扫描电子显微镜(FESEM)及气体反应控制器研究材料的相组成、微观形貌和吸放氢性能。结果表明:Pd/MWCNTs大幅提高HCS过程中Mg的氢化程度,在HCS过程中形成的Mg Pd合金明显提高复合材料的储氢性能。样品95Mg-2Pd/3MWCNTs在473 K下、100 s内,饱和吸氢量达到6.66%(质量分数);在573 K下、1 800 s内,放氢量高达6.25%(质量分数);其放氢的表观活化能与市售Mg H2相比,从153 k J/mol降低到80.8 k J/mol。

Multi-wall carbon nanotubes （MWCNTs） with different amounts of Pd （10％,20％,30％ and 40％） were synthesized by a solution reduction method.95Mg-mPd/（5-m） MWCNTs （m =0.5,1,1.5 and 2） were prepared by hydriding combustion synthesis （HCS） and mechanical milling （MM）.The phase compositions,surface morphologies and hydriding/dehydriding properties of the samples were examined by X-ray diffraction （XRD）,field emission scanning electron microscopy （FESEM）,transmission electron microscope （TEM）,and gas reaction controller.Results showed that Pd/MWCNTs could significantly increase the hydrogenation degree of magnesium during the HCS process.The MgPd alloy made the dehydrogenation process of MgH2 easier.The 95Mg-2Pd/3MWCNTs showed best hydriding/dehydriding properties,requiring only 100 s to reach its saturated hydrogen absorption capacity of 6.66％ at 473 K,and desorbing 6.25％ hydrogen within 1 800 s at 573 K.Additionally,the dehydrogenation activation energy of MgH2 in the system decreased from 153 kJ/mol to 80.8 kJ/mol.