铋系含氧酸盐改性镁水解制氢的动/热力学研究

Kinetic/thermodynamic study on improved hydrolysis hydrogen generation of Mg-doped bismuth series oxysalt

Mg基制氢材料具有来源广泛、反应温和、工艺简单、安全可控、理论产氢量高等优势,是当今的研究热点.本文提出采用高能球磨方法制备Mg-Bi系含氧酸盐Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)复合材料以改善Mg水解制氢性能.本工作研究发现,掺杂Bi_(2)Mo O_(6)的Mg基复合制氢材料具有较好的性能,Mg-7 wt%Bi_(2)Mo O_(6)在298.15 K的最大产氢速率为756.1 m L g^(-1)min(-1).通过引入多壁碳纳米管(CNTs)可以进一步改善Mg-Bi_(2)Mo O_(6)的产氢性能,Mg-7 wt%Bi_(2)Mo O_(6)/CNTs的最大产氢速率达2172.4 m L g^(-1)min(-1),产氢活化能下降至23.6 k J mol^(-1).X光电子能谱(XPS)分析表明Bi_(2)Mo O_(6)/CNTs与Mg在球磨过程中发生固相反应生成Bi单质.密度泛函理论(DFT)计算揭示Bi原子掺杂可改变Mg的局域电荷分布,增强Mg对H_(2)O的吸附能,并降低H_(2)O解离后H原子的吸附能,促进水解反应进行.

Study of high efficiency hydrogen production materials has attracted many researchers’attention.Mg-based hydrogen production material has the advantages of wide sources,mild reaction,simple process,safety control,and high hydrogen production capacity.In this article,Mg was doped with bismuth series oxysalt Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)by high energy ball milling method to improve the performance of hydrolytic hydrogen generation for the first time.It was found that Bi_(2)Mo O_(6)/CNTs enhanced the hydrogen generation performance of Mg and increased the initial hydrogen generation rate.The optimal hydrogen generation rate increased to 2172.4 m L g^(-1)min(-1),and the related activation energy decreased to 23.6 k J mol^(-1).Density functional theory(DFT)calculation found that doped Bi atom enhanced the adsorption of H_(2)O on Mg and reduced the adsorption of H atom by changing the local charge distribution,thus promoting the hydrolysis reaction.