Differences in NH3 gas adsorption behaviors of metal-hexacyanoferrate nanoparticles (Mx[FeII(CN)6]y•zH2O:M = In3+, Fe3+, and Mn2+)

Three different metal hexacyanoferrate nanoparticles (M-HCF-NPs, M = In3+, Fe3+, and Mn2+) were characterized by XRD, SEM, elemental analyses, IR and isotherm measurements. The obtained M-HCF-NPs prepared by a simple mixing procedure have a Prussian blue-type cubic crystal structure and sizes of around 20 nm. The chemical compositions measured by the elemental analyses are In-HCF = K0.039In[Fe(CN)(6)](0.75)center dot Cl-0.032 center dot 3.8H(2)O, Fe-HCF (PB) = K0.18Fe[Fe(CN)(6)](0.80)center dot 3.8H(2)O, and Mn-HCF = K1.3Mn[Fe(CN)(6)](0.84)center dot 1.3H(2)O. Ammonia gas iso-therms under vacuum revealed that the ammonia adsorption capacity of the M-HCF-NPs is in order of Mn < In Fe; however, the ammonia gas adsorption of In-HCF-NPs is faster than those of the Fe-HCF and MnHCF-NPs. This difference is considered to be caused by individual M-HCF structures, such as the vacancies in the HCF crystals, and by the interaction of individual M-HCF toward water molecules, which promote the conversion of NH3 species into stable NH4+ cations in M-HCF.