The enhanced ethanol sensing properties obtained by the introduction of NiO into ZnO/SnO₂ mixed metal oxides

Highlights: • Add a component with light responsive properties and fabricate p-n heterostructures in one-pot. • Visible light responsive component of NiO has been introduced into metal oxide composite sensors. • The p-n heterostructures between NiO and ZnSn-MMOCs are responsible to the sensing properties. • Visible light responsive component of NiO is very helpful to enhance the sensing response. - Abstract: NiO has been introduced into ZnSn-mixed metal oxide composites (MMOCs) with various Ni contents via a simple co-precipitation/sintering route. The influences of introduction of NiO on light absorption and ethanol sensing properties of ZnSn-MMOCs have been investigated. The obtained ternary NiZnSn-MMOCs exhibit extended adsorption to visible light area and lower energy band gap values. Consequently, their sensitivities and responses to ethanol have been enhanced by the introduction of NiO at certain range compared to binary ZnSn-MMOCs, which is attributed to the visible light responsive component of NiO and the p-n heterostructures between NiO and ZnSn-MMOCs. The ternary NiZnSn-MMOCs with the optimal content of NiO reveal high sensitivity of 180–200 ppm of ethanol at 225 °C and quick response time to low concentration of ethanol.