ABSTRACT
The utilization and selectivity of single atoms have garnered significant attention among researchers. However, they are easy to agglomerate because of their high surface energy. To overcome this challenge, it is crucial to seek suitable carriers to anchor single metal atoms to achieve optimal performance. In this work, the structures of transition metal single atoms embedded in hexagonal boron nitride (MB2N2, M = Fe, Co, Ni, Cu, Zn) are constructed and used for the adsorption and sensing of lithium battery thermal runaway gases (H2, CO, CO2, CH4) through the DFT method. The adsorption behavior of MB2N2 was evaluated through the adsorption energy, sensitivity, and recovery time. The calculation results indicate that CoB2N2 exhibits strong adsorption capacity for both H2 and CO. The sensitivity of FeB2N2 toward CO is as high as 3.232 × 1016. Subsequently, the adsorption mechanism was studied through TDOS and PDOS, and the results showed that hybridization between orbitals enhanced the gas adsorption performance. This study presents novel approaches for designing single-atom carriers and developing MB2N2 sensors for detecting lithium battery thermal runaway gases.
ABSTRACT
The detection of hazardous CO gas is an important research content in the domain of the Internet of Things (IoT). Herein, we introduced a facile metal-organic frameworks (MOFs)-templated strategy to synthesize Cd-doped Co3O4 nanosheets (Cd-Co3O4 NSs) aimed at boosting the CO-sensing performance. The synthesized Cd-Co3O4 NSs feature a multihole nanomeshes structure and a large specific surface area (106.579 m2·g-1), which endows the sensing materials with favorable gas diffusion and interaction ability. Furthermore, compared with unadulterated Co3O4, the 2 mol % Cd-doped Co3O4 (2% Cd-Co3O4) sensor exhibits enhanced sensitivity (244%) to 100 ppm CO at 200 °C and a comparatively low experimental limit of detection (0.5 ppm/experimental value). The 2% Cd-Co3O4 NSs show good selectivity, reproducibility, and long-term stability. The improved CO sensitivity signal is probably owing to the stable nanomeshes construction, high surface area, and rich oxygen vacancies caused by cadmium doping. This study presents a facile avenue to promote the sensing performance of p-type metal oxide semiconductors by enhancing the surface activity of Co3O4 combined with morphology control and component regulation.
ABSTRACT
To investigate the application of modified hexagonal boron nitride (h-BN) in the detection and monitoring of harmful gases (NO2, NO, NH3, and CO), first-principles calculations are applied to study the geometric structure and electronic behavior of the adsorption system. In this paper, the four adsorption sites, namely, B, N, bridge, and hollow sites, are considered to explore the stable adsorption structure of metals (M = Rh, Pd, Ag, Ir, Pt, and Au) on the BN surface. The calculation results demonstrate that the geometric structures of metal at the N-site are relatively stable. Subsequently, the different adsorption structures of NO2, NO, NH3, and CO on M-BN are researched. The electron transfer, charge difference density, and work function of the stable adsorption structure are calculated. The results show that NO2, NO, and CO have the strongest adsorption capacity in the Ir-BN system, with adsorption energies of -2.705, -5.064, and -3.757 eV, respectively. The Pt-BN system has an excellent adsorption performance (-2.251 eV) for NH3. Compared with the M-BN system, the work function of the adsorption system increases after adsorbing NO2, while it decreases after adsorbing NH3. This work shows that h-BN with metal modification is a potential material for online monitoring of harmful gases.
ABSTRACT
Platinum (Pt) nanoparticles/nanoclusters are some of the most efficient cocatalysts for photocatalytic CO2 reduction. Nevertheless, the produced CO can lead to a poisoning effect due to the strong adsorption strength of the Pt cocatalysts. Using density functional theory, PtOx clusters with variable sizes (Pt4O6, Pt5O8, Pt7O10, and Pt8O13) are selected to load on WS2 (PtOx-WS2) for photocatalytic CO2 conversion. The calculated results demonstrate that PtOx-WS2 are highly stable, and the electron-rich PtOx clusters are beneficial for the photocatalytic CO2 reduction. All the PtOx-WS2 catalysts exhibit efficient photocatalytic performance for CO2 reduction. Especially, Pt4O6-, Pt5O8-, and Pt8O13-WS2 have acceptable or ultra-low ΔGmax (ΔG for the rate-determining step) of 0.57, 0.23, and 0.48 eV to produce CH3OH, HCOOH, and CH4, respectively. The photocatalytic activities of PtOx-WS2 are correlated with the adsorption strength of the key intermediates, and the strong interactions between PtOx-WS2 and *COOH or *HCOO can lower the free energy changes for the first hydrogenation step. More importantly, PtOx-WS2 can also weaken the adsorption strength of *CO and *HCOOH, which are conducive to forming *CHO. This work gives an in-depth insight to design novel catalysts and promote their catalytic activity for photocatalytic CO2 reduction.
ABSTRACT
Based on the first principles of the GGA method, the magnetic and optical properties of intrinsic SnS2; Fe, Cr mono-doped SnS2; and (Fe, Cr) co-doped SnS2 are studied. The results show that the ground states of Fe, Cr mono-doped SnS2 are spin polarized, and the magnetic moments caused are 1.99 µB and 3.00 µB, respectively. The magnetic moment of Fe mono-doped SnS2 is mainly produced by Fe:3d orbitals, and the magnetic moment of Cr mono-doped SnS2 is mainly produced by Cr:3d and Sn:4d orbitals. We calculate that in the (Fe, Cr) co-doped SnS2 system, Fe, Cr and the adjacent S atoms form a strong hybrid, that is, the closest S atom between Fe and Cr atoms mediates the spin polarization and ferromagnetic (FM) coupling. This promotes the formation of a Fe:3d-S:3p-Cr:3d coupling chain, so that (Fe, Cr) co-doped SnS2 obtains FM stability. In addition, with the introduction of Fe and Cr atoms, the absorption coefficient is the largest in the long-wavelength infrared region of 0.23-1.63 eV. This shows that Fe and Cr doping can make up for the lack of absorption of intrinsic materials in the infrared region. In summary, Fe, Cr doped SnS2 dilute magnetic semiconductors may be a good candidate in the field of spintronic devices.
