Facile Synthesis of Co₃O₄/CoMoO₄ Heterostructure Nanosheets for Enhanced Acetone Detection

Although p-type semiconductors exhibit highly selective and stable chemiresistive gas sensing performances compared to conventional n-type semiconductors, their low sensitivity had long impeded their practical development. In this work, we developed highly porous Co₃O₄/CoMoO₄ heterostructure nanosheets (NSs) with enhanced sensitivity and superior stability toward acetone gas through a facile solution-based approach with Mo-impregnated Co-based metal-organic frameworks as the starting material. The spontaneous formation of a large number of p-p heterojunctions at the Co₃O₄-CoMoO₄ interface would facilitate the adsorption of oxygen and acetone molecules, as verified by density functional theory calculations. Consequently, experimental results showed that the Co₃O₄/CoMoO₄ NSs have a greatly enhanced response of 8.5 toward 5 ppm acetone, which is 7.1 times higher than that of pure Co₃O₄ NS, without involving any noble metal catalysts. Moreover, the limit of detection of the Co₃O₄/CoMoO₄ NSs was as low as 10 ppb. Altogether, we propose that our synthetic approach for the engineering of p-p heterojunctions is an effective strategy for the future development of highly practical and sensitive gas sensors based on p-type semiconductors.