MOF-derived Fe2O3: Phase control and effects of phase composition on gas sensing performance

Abstract Recently, the phase composition of a certain metal oxide has been regarded as an important factor that can significantly influence the gas sensing performance. For a better comparison, an appropriate method is necessary to control the phase composition of metal oxides. Herein, three Fe 2 O 3 samples with different phase compositions of α-Fe 2 O 3 , γ-Fe 2 O 3 and a mixed phase of α-Fe 2 O 3 and γ-Fe 2 O 3 were prepared by calcining MOF (metal-organic framework) templates at different temperatures. As-prepared Fe 2 O 3 samples have a similar morphologic structure but quite different gas sensing properties for VOCs (volatile organic compounds). Among them, α-Fe 2 O 3 has the smallest specific surface area, but the highest response toward n-butanol. It is indicated that α-Fe 2 O 3 and γ-Fe 2 O 3 have different gas sensing mechanisms. The sensitivity of α-Fe 2 O 3 comes from the concentration change of free carriers within the surface region. Differently, the transformation between γ-Fe 2 O 3 and Fe 3 O 4 determines the response of γ-Fe 2 O 3 . The findings can be used in the design of Fe 2 O 3 gas sensing materials in the future.