Fabrication of novel Ag-doped ZnO/CdO heterostructure for high-sensitive detection of formaldehyde at low temperature

•Ag-doped ZnO/CdO ternary heterostructure have been synthesized.•The ternary composite exhibited enhanced HCHO sensing property at low temperature.•The AZC-2 sensor reached a high response value of 164 to 50 ppm HCHO at 150 °C.•A low experimental detection limit of 100 ppb can be achieved.•Both the Ag doping and multiple heterojunctions contribute to the property improvement.