Environmentally friendly room temperature synthesis and humidity sensing applications of nanostructured Bi2O2CO3

Bi2O2CO3 nanosheets with exposed {0 0 1} facets were obtained from the straightforward and economic room temperature conversion of commercial Bi2O3 with CO2 as atmospheric carbon source. The growth process of Bi2O2CO3 was investigated with a variety of analytical methods including X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). (BiO)4CO3(OH)2 was identified as an intermediate during the transformation of bulk Bi2O3 into Bi2O2CO3 nanosheets. The humidity sensing tests indicated high sensitivities with impedance changes of 4 orders and capacitance changes of 3 orders of magnitude over a relative humidity (RH) range from 11 to 95%. Moreover, the humidity sensor based on Bi2O2CO3 nanosheets revealed a narrow humidity hysteresis, rapid response and recovery time with good reproducibility. These results demonstrated that Bi2O2CO3 is a promising humidity sensing material for environmental monitoring and humidity control.