High-valence cations-doped mesoporous nickel oxides nanowires: Nanocasting synthesis, microstructures and improved gas-sensing performance

[Display omitted] •All samples possess mesoporous-structure with the same diameter and similar structure.•The doped concentration decreases with the valence for the larger hydrated ion.•Mesoporous-structure with the higher surface area leads to the better response.•High-valence donor-doping further improves the response of NiO NWs.•High-valence ions supply extra electrons to combine holes to increase resistance. Mesoporous p-type nickel oxides nanowires (NiO NWs) and Li-, Zn-, Fe- and Sn-doped NiO NWs were synthesized with the nanocasting method, and then the influence of different valence cations doping on components, microstructure and gas-sensing performance was discussed in detail. All as-prepared NiO NWs with the same diameter exist in bundles and present mesoporous-structure, while the doping concentrations decrease with the increasing hydrated ions radius of Zn, Fe and Sn. The gas-sensing results indicate that the different valence cations doping greatly affects the gas-sensing properties of NiO NWs sensors. Li-doped NiO NWs sensor exhibits the decreased response to ethanol gas for the acceptor doping and Zn-doping weakly improve the response of NiO NWs sensor for the defects from the substitution of Ni. The responses are greatly enhanced by the high-valence Fe and Sn doping and Sn-doped NiO NWs sensor presents the highest sensitivity at the high concentration. The extra electrons from the high-valence Fe and Sn donor-doping recombine with the holes in valence band, which leads to the thicker hole-accumulation layer in air and the higher resistance of NiO NWs. In this way, the gas response of mesoporous NiO NWs sensor could be further improved with the high-valence donor-doping through adjusting the carrier concentration.