Penta-BeP 2 Monolayer: A Superior Sensor for Detecting Toxic Gases in the Air with Excellent Sensitivity, Selectivity, and Reversibility.

Directly and quickly detecting toxic gases in the air is urgently needed in industrial production and our daily life. However, the poor gas selectivity and low sensitivity under ambient conditions limit the development of gas sensors. In this work, we demonstrate that the penta-BeP 2 monolayer is an excellent toxic gas sensor by using first-principles calculations. The calculated results show that the semiconducting penta-BeP 2 monolayer can chemisorb toxic gas molecules (including CO, NH 3 , NO, and NO 2 ) with distinct charge transfer (-0.182 to 1.129 e) but negligibly interact with ambient gas molecules (including H 2 , N 2 , H 2 O, O 2 , and CO 2 ), indicating high gas selectivity for primary environmental gases. The calculated I-V curves show that the penta-BeP 2 monolayer exhibits a fast response with toxic gas molecules. Upon interaction with CO, NH 3 , NO, and NO 2 molecules at a bias voltage of 0.7 V, the currents are 10.23, 14.48, 32.10, and 129.90 times that of the pristine penta-BeP 2 monolayer, respectively, which induces high sensitivity values of 9.23, 13.48, 31.10, and 128.90, respectively. Moreover, the moderate adsorption energies of all toxic gas molecules guarantee that the penta-BeP 2 monolayer possesses good reversibility at room temperature with a short recovery time. Herein, all of our results indicate that the penta-BeP 2 monolayer could be a superior candidate for sensing toxic gases with high selectivity, sensitivity, and reversibility.