Synergetically Selective Toluene Sensing in Hematite‐Decorated Nickel Oxide Nanocorals

The decoration of p ‐type nickel oxide (NiO) with n ‐type hematite (α‐Fe 2 O 3 ) to achieve vertically ordered 1D nanostructures is an attractive strategy to enhance gas sensing properties. Herein, the authors report a facile method for α‐Fe 2 O 3 decoration of the whole surface of vertical NiO nanorods. An NiO/Fe heterostructure is deposited in multiple steps using a glancing angle deposition method, which is followed by the oxidation of Fe into α‐Fe 2 O 3 . Thermally agglomerated α‐Fe 2 O 3 nanoparticles are uniformly distributed on the whole surface of the NiO nanorods. Due to the α‐Fe 2 O 3 decoration, the NiO nanorods exhibit a coral‐like rough surface and, more interestingly, their preferential crystallographic orientation changed from (111) to (200). Compared to bare NiO nanorods, the α‐Fe 2 O 3 ‐decorated NiO nanocorals exhibit a 45.4 times higher response to 50 ppm toluene (C 7 H 8 ) at 350 °C. Their theoretical detection limit for C 7 H 8 is calculated to be ≈22 ppb. The observed unprecedented synergetic effects of α‐Fe 2 O 3 ‐decorated NiO nanocorals for the extremely selective C 7 H 8 sensing, as well as their facile synthetic route, establish a new perspective on heterostructured metal oxide 1D nanostructures for selective gas sensing.