Synergetically Selective Toluene Sensing in Hematite‐Decorated Nickel Oxide Nanocorals

The decoration of p‐type nickel oxide (NiO) with n‐type hematite (α‐Fe2O3) to achieve vertically ordered 1D nanostructures is an attractive strategy to enhance gas sensing properties. Herein, the authors report a facile method for α‐Fe2O3 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‐Fe2O3. Thermally agglomerated α‐Fe2O3 nanoparticles are uniformly distributed on the whole surface of the NiO nanorods. Due to the α‐Fe2O3 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‐Fe2O3‐decorated NiO nanocorals exhibit a 45.4 times higher response to 50 ppm toluene (C7H8) at 350 °C. Their theoretical detection limit for C7H8 is calculated to be ≈22 ppb. The observed unprecedented synergetic effects of α‐Fe2O3‐decorated NiO nanocorals for the extremely selective C7H8 sensing, as well as their facile synthetic route, establish a new perspective on heterostructured metal oxide 1D nanostructures for selective gas sensing.