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

In this work, different sizes of α-Fe 2 O 3 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-Fe 2 O 3 and γ-Fe 2 O 3 , then transformed into α-Fe 2 O 3 to reach the final thermodynamically stable stage . By aiming H 2 S as target gas, the gas-sensing performance of the pure phase α-Fe 2 O 3 hollow cubes with different sizes was explored, which demonstrate high sensitivity to H 2 S gas at room temperature, as well as ideal stability and selectivity. Interestingly, the response value of four sizes of α-Fe 2 O 3 to 5 ppm H 2 S 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-Fe 2 O 3 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-Fe 2 O 3 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-Fe 2 O 3 cube. • Controllable synthesis of different sizes of α-Fe 2 O 3 hollow. • Kinetic transformation of PB to β-Fe 2 O 3 and γ-Fe 2 O 3 , then to the most thermodynamically stable α-Fe 2 O 3 . • Novel selectivity, repeatability and stability of α-Fe 2 O 3 hollow cubes’ gas sensing performance to H 2 S at room-temperature. • Insight into the gas sensing mechanism of the joint effect of oxygen vacancies and specific surface area.