Cu2O–CuO composite microframes with well-designed micro/nano structures fabricated via controllable etching of Cu2O microcubes for CO gas sensors

Composite materials with well-designed structures have been extensively explored to enhance their sensing performances. Here, through a simple “top-down” chemical etching approach, Cu2O–CuO composite microframes were fabricated with many nanometer-sized branch-like nanorods distributed on the surfaces and edges. The structure evolution was monitored and the synergistic process of the oxidation effect and Kirkendall diffusion was proposed to explain the formation mechanism of the structure. The Cu2O–CuO microframes show enhanced gas sensing properties towards CO with a lower detection limit, a higher sensitivity and a shorter response time than pure CuO microcubes and Cu2O microcubes at the working temperature of 240 °C. The enhanced sensing performance of the Cu2O–CuO microframe is probably attributed to the additional depletion layer formed between CuO and Cu2O, as well as the structural advantages of the microframe.