Enhancing the Hydrogen-Sensing Performance of p-Type PdO by Modulating the Conduction Model

Dispersive Pd islands-deposited Au nanorods for in situ SERS monitoring of catalytic reaction

In this study, a bifunctional material with SERS effect and catalytic performance is fabricated in which dispersive Pd islands are deposited on the surface of gold nonorods (AuNR@Pd islands) with the confined modification of surface active sites of AuNRs using 5-iodo salicylic acid (5-ISA), which optimize the performance of bifunctional materials.

Highly Sensitive Ethylene Glycol Gas Sensor Based on MIL-68(In)@ZIF-8 Derivative

Ethylene glycol, as a colorless and tasteless organic compound, is an important industrial raw material but can be hazardous to the environment and human health. Thus, the development of high-performance sensing materials is required for the monitoring of ethylene glycol. In this paper, a method to synthesize In2O3@ZnO using MIL-68(In)@ZIF-8 to serve as a sacrificial template is proposed for testing ethylene glycol sensing capabilities. For verifying an effective improvement in gas-sensitive performance by bimetallic organic skeleton (MOF) synthesized heterojunctions, we performed gas-sensitive tests on In2O3, ZnO, and In2O3@ZnO. In2O3@ZnO has the best sensitivity to ethylene glycol, including ultrahigh response value (20 ppm-200.12), moderate response/recovery time (53/50 s), and excellent selectivity. The construction of heterojunction is the main reason for enhancing the ethylene glycol response of the sensor. On this basis, the gas-sensitive enhancement mechanism of composites is analyzed. The results show that the design method of synthesizing heterojunctions using bis-MOFs proposes a new approach that enhances the properties of ethylene glycol.

Critical Sensing Modalities for Hydrogen: Technical Needs and Status of the Field to Support a Changing Energy Landscape

Decarbonization of the energy system is a key aspect of the energy transition. Energy storage in the form of chemical bonds has long been viewed as an optimal scheme for energy conversion. With advances in systems engineering, hydrogen has the potential to become a low cost, low emission, energy carrier. However, hydrogen is difficult to contain, it exhibits a low flammability limit (>40000 ppm or 4%), low ignition energy (0.02 mJ), and it is a short-lived climate forcer. Beyond commercially available sensors to ensure safety through spot checks in enclosed environments, new sensors are necessary to support the development of low emission infrastructure for production, transmission, storage, and end use. Efficient scalable broad area hydrogen monitoring motivates lowering the detection limit below that (10 ppm) of best in class commercial technologies. In this perspective, we evaluate recent advances in hydrogen gas sensing to highlight technologies that may find broad utility in the hydrogen sector. It is clear in the near term that a sensor technology suite is required to meet the variable constraints (e.g., power, size/weight, connectivity, cost) that characterize the breadth of the application space, ranging from industrial complexes to remote pipelines. This perspective is not intended to be another standard hydrogen sensor review, but rather provide a critical evaluation of technologies with detection limits preferably below 1 ppm and low power requirements. Given projections for rapid market growth, promising techniques will also be amenable to rapid development in technical readiness for commercial deployment. As such, methods that do not meet these requirements will not be considered in depth.

Pd Decoration with Synergistic High Oxygen Mobility Boosts Hydrogen Sensing Performance at Low Working Temperature on WO3 Nanosheet

Pd-based materials have received remarkable attention and exhibit excellent H2 sensing performance due to their superior hydrogen storage and catalysis behavior. However, the synergistic effects originated from the decoration of Pd on a metal oxide support to boost the sensing performance are ambiguous, and the deep investigation of metal support interaction (MSI) on the H2 sensing mechanism is still unclear. Here, the model material of Pd nanoparticle-decorated WO3 nanosheet is synthesized, and individual fine structures can be achieved by treating it at different temperatures. Notably, the Pd-WO3-300 materials display superior H2 sensing performance at a low working temperature (110 °C), with a superior sensing response (Ra/Rg = 40.63 to 10 ppm), high sensing selectivity, and anti-interference ability. DFT calculations and detailed structural investigations confirm that the moderate MSI facilitates the generation of high mobility surface O2- (ad) species and a proper ratio of surface Pd0-Pd2+ species, which can significantly boost the desorption of intermediate PdHx species at low temperatures and contribute to enhanced sensing performance. Our work illustrates the effect of MSI on sensing performance and provides insight into the design of advanced sensing materials.

Hydrogen-Induced Aggregation of Au@Pd Nanoparticles for Eye-Readable Plasmonic Hydrogen Sensors

Plasmonic materials provide a promising platform for optical hydrogen detection, but their sensitivities remain limited. Herein, a new type of eye-readable H₂ sensor based on Au@Pd core-shell nanoparticle arrays (NAs) is reported. After exposed to 2% H₂, Au@Pd (16/2) NAs demonstrate a dramatic decrease in the optical extinction intensity, along with an obvious color change from turquoise to gray. Experimental results and theoretical calculations prove that the huge optical change resulted from the H₂-induced aggregation of Au@Pd nanoparticles (NPs), which remarkably alters the plasmon coupling effect between NPs. Moreover, we optimize the sensing behavior from two aspects. The first is selecting appropriate substrates (either rigid glass substrate or flexible polyethylene terephthalate substrate) to offer moderate adhesion force to NAs, ensuring an efficient aggregation of Au@Pd NPs upon H₂ exposure. The second is adjusting the Pd shell thickness to control the extent of NP aggregation and thus the detection range of the as-prepared sensors. This work highlights the advantage of designing eye-readable plasmonic H₂ sensors from the aspect of tuning the interparticle plasmonic coupling in NP assemblies. Au@Pd NAs presented here have several advantages in terms of simple fabrication method, eye-readability in air background at room temperature, tunable detection range, and high cost-effectiveness.

Controllable Fabrication of PdO-PdAu Ternary Hollow Shells: Synergistic Acceleration of H2 -Sensing Speed via Morphology Regulation and Electronic Structure Modulation

Designing ultrafast H₂ sensors is of particular importance for practical applications of hydrogen energy but still quite challenging. Herein, PdO decorated PdAu ternary hollow shells (PdO-PdAu HSs) exhibiting an ultrafast response of ≈0.9 s to 1% H₂ in air at room temperature are presented. PdO-PdAu HSs are fabricated by calcinating PdAu bimetallic HSs in air to form PdO-Au binary HSs, which are then partially reduced by NaBH₄ solution, forming PdO-PdAu HSs. This ternary hybrid material takes advantage of multiple aspects to synergistically accelerate the sensing speed. The HS morphology promises high gas accessibility and high surface area for H₂ adsorption, and decoration of Au and PdO alters the electronic state of Pd and reduces the energy barrier for hydrogen diffusing from the surface site of Pd into the subsurface site. The content of Au and PdO in the ternary HSs can be simply tuned, which offers the possibility to optimize their promotion effects to reach the best performance. The proposed fabrication strategy sheds light on the rational design of ultrafast Pd-based H₂ sensors by controlling the sensor structure and engineering the electronic state of active species.