Co₃O₄ Nanosheets Decorated with In₂O₃ Nanocubes with Exposed {001} Facets for ppb-Level CO Sensing

Abstract

To selectively detect trace carbon monoxide (CO typically lower than 100 ppb) at low temperature is still a great challenge for chemiresistive gas sensors. In this work, we introduce In 2 O 3 nanocubes with exposed {001} facets to couple with MOFderived porous Co 3 O 4 nanosheets (NSs) forming p−n heterojunction for trace CO detection. Benefiting from the vacancy storing effect of the sub-valent band on In 2 O 3 nanocube {001} facets and the p−n heterojunction effect, the electron−hole recombination is effectively inhibited, and the carrier lifetime is prolonged. As a result, the prepared CoIn0.1-based gas sensor shows a good selectivity and ultralow detection limitation of 25 ppb toward CO at relatively low temperature of 175 °C. In addition, the CoIn0.1-based CO sensor also exhibits high response (272.89%) and ultrafast response/ recovery time (2 s/13 s) to 100 ppm CO, which can be ascribed to the fast gas diffusion in the porous Co 3 O 4 NSs and the highindex facet effect of In 2 O 3 nanocubes. This work provides a method to design and synthesize trace CO gas sensors via modulating the band structure of p−n heterojunctions constructed by two-dimensional metal oxide NSs and oxide-exposed high-index facets. KEYWORDS: CO gas sensors, ppb-level, Co 3 O 4 nanosheets, In 2 O 3 nanocubes, heterostructure

Elaborately tailored NiCo2O4 for highly efficient overall water splitting and urea electrolysis

“…These Co 2+ peaks are accompanied by two satellite peaks, denoted as "Sat". This observation provides evidence for the coexistence of low spin Co 2+ and Co 3+ in Ru-NiCo 2 O 4 41,42. Fig.…”

“…This observation provides evidence for the coexistence of low spin Co 2+ and Co 3+ in Ru-NiCo 2 O 4 . 41,42 Fig. 2c displays the Ni 2p spectrum of Ru-NiCo 2 O 4 , wherein the two peaks observed at 873.93 eV and 871.68 eV correspond to Ni 2p 1/2 , while the additional peaks at 855.88 eV and 854.08 eV can be ascribed to the Ni 2p 3/2 .…”

Interface Defects and Carrier Regulation in MOF-Derived Co3O4/In2O3 Composite Materials for Enhanced Selective Detection of HCHO

“…Both In 2 O 3 and Co 3 O 4 retained the original framework structure of MOFs (Figure S2a,b), exhibiting rough surfaces with numerous pores and cracks, which may be caused by the Kirkendall effect and the volatilization and decomposition of organic ligands during annealing . In the transmission electron microscopy (TEM) image (Figure c), it is clearly observed that the framework structure of In 2 O 3 and Co 3 O 4 undergoes a hierarchical heterogeneous contact, and the strong surface electronic interaction between the different phases during the secondary calcination favors an increase in the surface defect content . The HRTEM image (Figure d) further confirmed this observation, with lattice fringes of widths of 0.29 and 0.48 nm corresponding to the (222) crystal planes of cubic In 2 O 3 and the (111) crystal planes of spinel Co 3 O 4 , respectively.…”

“…The grain size was approximately 10 nm, and the lattice strain slightly increased with the increasing modification load, further supporting the possibility of increased surface defects caused by this surface modification method. , The phase structure of the surface Co 3 O 4 can be obtained within a narrower range by using laser confocal Raman microscopy (Raman). In Figure f, the pure In 2 O 3 material exhibits five Raman-active vibration peaks in the range of 50–800 cm –1 , all of which can be attributed to the cubic phase of In 2 O 3 . , Under excitation at a wavelength of 514 nm, the MZO material shows strong Raman activity in the selected area, with the sharp characteristic peaks at 191, 474, 514, 610, and 677 cm –1 corresponding to the F 2g , E g , F 2g , F 2g , and A 1g Raman vibration modes of the five spinel phases of Co 3 O 4 , respectively . At the same time, the characteristic peak of cubic-phase In 2 O 3 appears at 131 cm –1 .…”

Crystallographic Nanojunctions of Bismuth Ferrite for Unconventional Detection of Carbon Monoxide

“…A study conducted by Wang et al showcased the efficacy of a Pd-doped CoTiO 3 /TiO 2 p–n heterojunction device in detecting benzene by augmenting the catalytic activity of Pd. Additionally, the researchers also exhibited an enhancement in the gas sensing capabilities of a ZnO/SnSe-based CO sensor through the stimulation of photoelectrons in the presence of ultraviolet light. , Chen et al presented the utilization of In 2 O 3 nanocubes that possess exposed {001} facets in conjunction with MOF-derived porous Co 3 O 4 nanosheets (NSs) to create a p–n heterojunction for the purpose of detecting trace amounts of CO . Hu et al developed Pd-doped In 2 O 3 /CeO 2 heterojunction nanofibers using electrospinning and DC sputtering to detect hydrogen gas.…”