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

Abstract

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 Co 3 O 4 /CoMoO 4 heterostructure nanosheets (NSs) with enhanced sensitivity and superior stability toward acetone gas through a facile solutionbased 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 Co 3 O 4 −CoMoO 4 interface would facilitate the adsorption of oxygen and acetone molecules, as verified by density functional theory calculations. Consequently, experimental results showed that the Co 3 O 4 /CoMoO 4 NSs have a greatly enhanced response of 8.5 toward 5 ppm acetone, which is 7.1 times higher than that of pure Co 3 O 4 NS, without involving any noble metal catalysts. Moreover, the limit of detection of the Co 3 O 4 / CoMoO 4 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.

Surface Modulation of Co3O4 Yolk–Shell Spheres with Tungsten Doping for Superior Acetone Sensitivity

“…The full XPS spectra of W-doped Co 3 O 4 YSS revealed the coexistence of Co 2p, O 1s, and W 4f peaks (Figure e), confirming the mixed oxide composition. More specifically, the Co 2p 3/2 region (Figure f) showed two distinct peaks of Co 3+ (779.36 eV) and Co 2+ (780.84 eV), confirming the coexistence of Co 2+ and Co 3+ in the as-synthesized YSS, supporting the formation of Co 3 O 4 with a spinel structure . The well-resolved doublet peaks in the W 4f region, as shown in Figure h, represent the 4f 7/2 (34.66 eV) and 4f 5/2 (36.73 eV) of W 6+ , respectively.…”

“…More specifically, the Co 2p 3/2 region (Figure 4f) showed two distinct peaks of Co 3+ (779.36 eV) and Co 2+ (780.84 eV), confirming the coexistence of Co 2+ and Co 3+ in the assynthesized YSS, supporting the formation of Co 3 O 4 with a spinel structure. 36 The well-resolved doublet peaks in the W 4f region, as shown in Figure 3h, represent the 4f 7/2 (34.66 eV) and 4f 5/2 (36.73 eV) of W 6+ , respectively. In fact, compared to tabulated values for pristine WO 3 , these binding energies are slightly weaker, indicating the presence of ionic tungsten incorporated into the Co 3 O 4 YSS matrix instead of a separate WO 3 phase.…”

“…Optimizing the working temperature is crucial in determining gas-sensing performance, as it directly affects the surface adsorption behavior of gases. Thus, to determine the optimal working temperature, we exposed the sensors to 5 ppm of acetone gas at various working temperatures (200–350 °C). , As shown in Figures b and S9, the 1.0W-Co 3 O 4 YSS exhibited the highest response of 16.5 toward 5 ppm of acetone gas at 250 °C, which exceeds that of Co 3 O 4 YSS (2.9), 0.5W-Co 3 O 4 YSS (5.3), and 1.5W-Co 3 O 4 YSS (5.1) by a significant margin. Thereafter, to evaluate the dynamic sensing performance, sensors were exposed to acetone gas concentrations ranging from 10 ppb to 5 ppm at a working temperature of 250 °C.…”

Enhanced toluene sensing performances over commercial Co3O4 modulated by oxygen vacancy via NaBH4-assisted reduction approach

“…On the one hand, p-type metal oxides exhibit better catalytic activity than that of n-type metal oxides 7,8 and have been widely used as catalysts toward the catalytic oxidation of different VOCs. 9,10 On the other hand, p-type metal oxides can chemisorb more oxygen molecules than n-type metal oxides, subsequently forming more active sites to react with the target gas, and thus can be employed to fabricate gas sensors with excellent selectivity toward VOCs.…”

Target-Driven Z-Scheme Heterojunction Formation for ppb H2S Detection from Exhaled Breath at Room Temperature

“…Chemiresistor gas sensors are widely used owing to their ease of preparation, high sensitivity, and simple backend electrical signal processing . Conventional semiconducting metal oxides, such as CuO, SnO 2 , WO 3 , TiO 2 , and Co 3 O 4 , are widely used in gas sensors to detect harmful gases. − However, poor selectivity and high operating temperature are still the cruxes of semiconducting metal oxide-based gas sensors, causing the practical indicators for the effective detection of exhaled air biomarkers unsatisfactory, especially in the sensitivity and detection limit of ppb-grade gases . In recent years, substantial progress has been made to improve the gas sensing property of materials at room temperature (RT).…”