Oxygen Vacancies Induced by Pd Doping in Ni-P₂O₅/MoO₃ Hollow Polyhedral Heterostructures for Highly Efficient Diethylamine Gas Sensing

Abstract

Semiconductor metal-oxide materials have a high surface-to-volume ratio and many active sites, making them potentially useful for gas sensing. Dopants introduced into the lattice can improve the catalytic activity of oxides and promote the formation of oxygen vacancies, hence improving the sensing performance of the materials. However, the simple preparation of materials with high sensitivity, selectivity, and a low detection limit remains a challenge. Herein, we report on the synthesis of Ni-P2O5/MoO3 and Pd-doped Ni-P2O5/MoO3 hollow polyhedral heterostructures (HPHSs) and their application in diethylamine (DEA) sensing for the first time. The Pd-doped Ni-P2O5/MoO3 HPHS was synthesized by doping different proportions of palladium-containing precursors using hydrothermal and solid-state reaction techniques. The concentration of oxygen vacancies in the HPHS composite increased by increasing Pd doping from 2 to 6 weight percent (wt %) but later reduced, according to X-ray photoelectron spectroscopy (XPS) measurements. Pd6%Ni-P2O5/MoO3 has the highest sensitivity to DEA (R a/R g = 42.5) and is 5.0 times and 42.5 times more sensitive than the pure Ni-P2O5/MoO3 HPHS (R a/R g = 8.5) and commercial ammonium phosphomolybdate (R a/R g = 1) at 175 °C toward 10 ppm DEA. Moreover, the DEA sensor exhibits a low detection limit (R a/R g = 3.5@1 ppm) with a wide dynamic response (R a/R g = 145.5@50 ppm). The remarkable improvement in DEA sensitivity is attributed to the hollow polyhedral structure, heterostructures, and oxygen vacancies formed by Pd doping. This study confirms that developing Pd-doped Ni-P2O5/MoO3 HPHSs provides an innovative approach for DEA sensors.

Generation of Oxygen Vacancies in Metal–Organic Framework-Derived One-Dimensional Ni0.4Fe2.6O4 Nanorice Heterojunctions for ppb-Level Diethylamine Gas Sensing

“…The dominant peaks at 530.11, 532.11, and 533.31 eV are ascribed to lattice oxygen (O L ), O vs , and surface chemisorbed oxygen (O abs ), respectively . When Ar-Ni 0.4 Fe 2.6 O 4 NRs were compared to air-Ni 0.4 Fe 2.6 O 4 NRs, the O 1s peak of the Ar-Ni 0.4 Fe 2.6 O 4 NRs shifted slightly higher and the peak intensity increased considerably, indicating the production of O vs and increased catalytic activity after annealing NRs in an Ar atmosphere (Figure d). , XPS is a powerful and sophisticated tool for detecting O vs in composites. , When the relative area of the O vs peak was used to estimate its concentration, the results (Table S2) show that the concentration of O vs in Ar-Ni 0.4 Fe 2.6 O 4 NRs increased compared to that annealed in the air. The significant rise in the proportion of O vs indicates that Ar annealing promotes the formation of O vs .…”

“…29,56 XPS is a powerful and sophisticated tool for detecting O vs in composites. 29,57 When the relative area of the O vs peak was used to estimate its concentration, the results (Table S2) show that the concentration of O vs in Ar-Ni 0.4 Fe 2.6 O 4 NRs increased compared to that annealed in the air. The significant rise in the proportion of O vs indicates that Ar annealing promotes the formation of O vs .…”

Integration of High-Entropy Oxide with Nitrogen-Doped Graphene for the Ultrasensitive Electrochemiluminescence Detection of Trolox and Dopamine

“…The presence of elements Mg, Co, Cu, Ni, Zn, C, N, and O was identified by XPS survey spectra, as indexed in Figure S3. The high-resolution XPS spectra of Co 2p and Ni 2p show that both metals split into two spin orbitals and shakeup satellite peaks, indicating the presence of divalent and trivalent species, with a dominance of divalent ones (Figure a,b). − The Cu 2p spectrum signifies the coexistence of monovalent and divalent species, with a dominance of divalence (Figure c), whereas the Mg 1s and Zn 2p spectra reveal also that the corresponding elements are in divalence status (Mg 2+ and Zn 2+ ; Figure d,e). The N 1s spectrum (Figure f) indicates the presence of two deconvoluted peaks credited as pyridinic N (398.6 eV) and graphitic N (402.5 eV), which is assumed to contribute to improving the stability and catalytic activity of the resulting sample .…”

Ultrafast Response and High Selectivity of Diethylamine Gas Sensors at Room Temperature Using MOF-Derived 1D CuO Nano-Ellipsoids

“…Response time is the time it takes for the sensor resistance to change from its initial value (in the air) to 90% of its maximum value in the presence of DEA. 54 Similarly, recovery time is the time it takes for the sensor device resistance to shift from its maximum value (when DEA is present) to 10% over the base resistance. 54 The response and recovery periods of the CuO-400 NEs, CuO-600, and CuO-800 sensors to DEA of 5 ppm are determined to be 64/55, 69/ 65, and 70/75 s, respectively, as shown in Figure S8(a−c), indicating their quick response and excellent reversibility.…”