A p-n Heterojunction Based Pd/PdO@ZnO Organic Frameworks for High-Sensitivity Room-Temperature Formaldehyde Gas Sensor

Abstract

As formaldehyde is an extremely toxic volatile organic pollutant, a highly sensitive and selective gas sensor for low-concentration formaldehyde monitoring is of great importance. Herein, metal-organic framework (MOF) derived Pd/PdO@ZnO porous nanostructures were synthesized through hydrothermal method followed by calcination processes. Specifically, porous Pd/PdO@ZnO nanomaterials with large surfaces were synthesized using MOFs as sacrificial templates. During the calcination procedure, an optimized temperature of 500°C was used to form a stable structure. More importantly, intensive PdO@ZnO inside the material and composite interface provides lots of p-n heterojunction to efficiently manipulate room temperature sensing performance. As the height of the energy barrier at the junction of PdO@ZnO exponentially influences the sensor resistance, the Pd/PdO@ZnO nanomaterials exhibit high sensitivity (38.57% for 100 ppm) at room temperature for 1-ppm formaldehyde with satisfactory selectivity towards (ammonia, acetone, methanol, and IPA). Besides, due to the catalytic effect of Pd and PdO, the adsorption and desorption of the gas molecules are accelerated, and the response and recovery time is as small as 256 and 264 s, respectively. Therefore, this MOF-driven strategy can prepare metal oxide composites with high surface area, well-defined morphology, and satisfactory room-temperature formaldehyde gas sensing performance for indoor air quality control.

Three-Layer PdO/CuWO4/CuO System for Hydrogen Gas Sensing with Reduced Humidity Interference

“…Several strategies have been proposed and implemented to reduce the humidity interference in the sensing response [29][30][31][32]. Among others, one of the efficient strategies is the use of noble metal catalysts such as Pd, Pt, and their compounds [33][34][35].…”

Metal Nanocluster—Metal Organic Framework—Polymer Hybrid Nanomaterials for Improved Hydrogen Detection

“…In addition to their role as a selective gas filter for H 2 , metal-organic frameworks (MOFs) have also been used to derive Pd/PdO@ZnO porous nanostructures for enhanced formaldehyde gas sensing with good selectivity. [27] Meanwhile, we noticed that the hybridization of metal nanoclusters (NCs) and an MOF remarkably enhanced the catalytic ability of noble metal NCs [28,29] and even their hydrogen storage capacity. [30] Following this line of thinking, we propose a concept and for hybridization between a sensing element of Pd NCs and an MOF to construct an interfacial structure at the nanoscale.…”

Pd Clusters on Schiff Base–Imidazole-Functionalized MOFs for Highly Efficient Catalytic Suzuki Coupling Reactions

“…Metal−organic frameworks (MOFs) are a fascinating family of porous crystalline materials assembled with inorganic metal nodes and organic linkers, possessing large internal surface areas, well-defined structures, and tunable chemical properties ( Lee et al, 2009 ; Li et al, 2012 ; Furukawa et al, 2013 ). These features confer their popular applications in heterogeneous catalysis, particularly when they are used as support for noble metal (e.g., Pd, Au, Ru, and Pt) nanoparticles (MNPs) ( He et al, 2018 ; Han et al, 2019 ; Chen et al, 2021 ; Khan et al, 2021 ). On the one hand, the permanent porosity and uniform channels of MOFs make them particularly suitable for the efficient immobilization of MNPs that protect the MNPs from sintering and aggregation without inhibiting the diffusion of the reactants and products.…”

“…On the one hand, the permanent porosity and uniform channels of MOFs make them particularly suitable for the efficient immobilization of MNPs that protect the MNPs from sintering and aggregation without inhibiting the diffusion of the reactants and products. On the other hand, the organic linkers or the metal nods of MOFs can also be used as unique functional moieties, and the interaction between MOFs and MNPs can trigger excellent synergistic effects, affording properties that are superior to the individual components ( Fang et al, 2018 ; He et al, 2018 ; Mouarrawis et al, 2018 ; Han et al, 2019 ; Khan et al, 2021 ). Su et al constructed a series of novel MOFs based on redox-active tetrathiafulvalene (TTF) organic linkers.…”