Effect of laminate structure on morphology and ethanol sensing properties of hierarchical zinc–cobalt layered double hydroxides

Abstract

Layered double hydroxides (LDH) have attracted much attention in the gas sensing field due to their unique laminate structure and flexible chemical composition. In this work, the single crystalline nanosheet-assembled ZnCo-LDHs are synthesized by a facile one-pot hydrothermal route. We find that the Zn addition amount plays a vital role in tuning the Co²⁺/Co³⁺ ratio distributed in the laminate structure of LDH, further modulating the amount of oxygen defects. When the Zn/Co addition ratio is 1.8 in the synthetic system, the obtained ZnCo-LDH exhibits abundant exposed active sites due to its orderly arranged nanosheet structure. It also shows a favorable oxygen adsorption capability resulting from more oxygen defects in the laminate structure. The hierarchical structure facilitates gas diffusion and catalysis in sensing the redox process by cooperation of Zn²⁺ and Co³⁺. The obtained flower like ZnCo-LDH exhibits a high response of 19.19 to 200 ppm ethanol at working temperature as low as 80 °C. It also shows good selectivity and stability. The hierarchical ZnCo-LDHs provide a new chemiresistive sensing material with low energy consumption and high sensitivity.