Prussian blue-derived hollow cubic α-Fe2O3 for highly sensitive room temperature detection of H2S

Abstract

In this work, different sizes of α-Fe2O3 hollow cubic structures are prepared by calcination of Prussian blue templates with different sizes. Furthermore, the transformation mechanism is also investigated by applying different conversion temperatures to the same Prussian blue template. In specific, Prussian blue initially transformed into β-Fe2O3 and γ-Fe2O3, then transformed into α-Fe2O3 to reach the final thermodynamically stable stage. By aiming H2S as target gas, the gas-sensing performance of the pure phase α-Fe2O3 hollow cubes with different sizes was explored, which demonstrate high sensitivity to H2S gas at room temperature, as well as ideal stability and selectivity. Interestingly, the response value of four sizes of α-Fe2O3 to 5 ppm H2S are 1.17, 2.44, 4.67 and 1.15 respectively, which indicates that the gas-sensing response has a trend from rise to decline as the cube size increases. For α-Fe2O3 cube with size of 800 nm, it presents the optimized sensitivity. Finally, characterizations such as BET, XPS and PL reveal that with increment of α-Fe2O3 cube size, the specific surface area increases while the oxygen vacancy density decreases, whose joint influence is the mechanism for the optimized sensitivity of 800 nm α-Fe2O3 cube.