Institute of Surface Chemistry and Catalysis, Ulm University , D-89069 Ulm, Germany.
Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage , Helmholtzstr. 11, D-89081 Ulm, Germany.
ACS Appl Mater Interfaces. 2018 Jan 17;10(2):1662-1671. doi: 10.1021/acsami.7b13541. Epub 2018 Jan 2.
Two approaches of engineering surface structures of V-Ti-based solid solution hydrogen storage alloys are presented, which enable improved tolerance toward gaseous oxygen (O) impurities in hydrogen (H) gas. Surface modification is achieved through engineering lanthanum (La)- or nickel (Ni)-rich surface layers with enhanced cyclic stability in an H/O mixture. The formation of a Ni-rich surface layer does not improve the cycling stability in H/O mixtures. Mischmetal (Mm, a mixture of La and Ce) agglomerates are observed within the bulk and surface of the alloy when small amounts of this material are added during arc melting synthesis. These agglomerates provide hydrogen-transparent diffusion pathways into the bulk of the V-Ti-Cr-Fe hydrogen storage alloy when the remaining oxidized surface is already nontransparent for hydrogen. Thus, the cycling stability of the alloy is improved in an O-containing hydrogen environment as compared to the same alloy without addition of Mm. The obtained surface-engineered storage material still absorbs hydrogen after 20 cycles in a hydrogen-oxygen mixture, while the original material is already deactivated after 4 cycles.
介绍了两种工程化 V-Ti 基固溶体储氢合金表面结构的方法，使合金对氢气中气态氧（O）杂质具有更好的耐受性。表面改性是通过工程化富含镧（La）或镍（Ni）的表面层来实现的，在 H/O 混合物中具有增强的循环稳定性。在 H/O 混合物中，形成富 Ni 表面层并不能提高循环稳定性。当在电弧熔炼合成过程中添加少量这种材料时，在合金的体相和表面会观察到混合稀土（Mm，La 和 Ce 的混合物）团聚体。当剩余的氧化表面已经对氢气不透明时，这些团聚体为氢气提供了透明的扩散途径进入 V-Ti-Cr-Fe 储氢合金的体相。因此，与未添加 Mm 的相同合金相比，在含 O 的氢气环境中，合金的循环稳定性得到了提高。在氢-氧混合物中经过 20 次循环后，获得的表面工程化储氢材料仍能吸收氢气，而原始材料在经过 4 次循环后已经失活。
