A highly stable and sensitive ethanol sensor based on Ru-decorated 1D WO3 nanowires

Self-Supported WO3@RuO2 Nanowires for Electrocatalytic Acidic Water Oxidation

Developing catalysts with high catalytic activity and stability in acidic media is crucial for advancing hydrogen production in proton exchange membrane water electrolyzers (PEMWEs). To this end, a self-supported WO3@RuO2 nanowire structure was grown in situ on a titanium mesh using hydrothermal and ion-exchange methods. Despite a Ru loading of only 0.098 wt %, it achieves an overpotential of 246 mV for the oxygen evolution reaction (OER) at a current density of 10 mA·cm-2 in acidic 0.5 M H2SO4 while maintaining excellent stability over 50 h, much better than that of the commercial RuO2. After the establishment of the WO3@RuO2 heterostructure, a reduced overpotential of the rate-determining step from M-O* to M-OOH* is confirmed by the DFT calculation. Meanwhile, its enhanced OER kinetics are also greatly improved by this self-supported system in the absence of the organic binder, leading to a reduced interface resistance between active sites and electrolytes. This work presents a promising approach to minimize the use of noble metals for large-scale PEMWE applications.

Effective Reinforcement of Visible Light Photocatalytic and Gas Sensing Characteristics of Nanocrystalline TiO2: Gd-Based Nb and Mo Dopants

Efficient compositions for the selective detection of ethanol gas and the removal of organic contaminants were realized by codoping of (Gd, Nb) and (Gd, Mo) ions into TiO2. TiO2, Ti0.96Gd0.01Nb0.03O2, and Ti0.96Gd0.01Mo0.03O2 samples were prepared by a coprecipitation method. For all compositions, a crystalline anatase phase of TiO2 was detected. Compared to pure TiO2, the absorption edges of Ti0.96Gd0.01Nb0.03O2 and Ti0.96Gd0.01Mo0.03O2 samples were red-shifted, further broadening towards visible light. The morphological studies demonstrate that the grains of TiO2 were more refined after (Gd, Nb) and (Gd, Mo) codoping. The photocatalytic efficiency of the Ti0.96Gd0.01Mo0.03O2 catalyst for degrading 20 mg/L reactive yellow 145, brilliant green, and amoxicillin was 98, 95, and 93% in 90 min, respectively. The reusability experiments indicate that the Ti0.96Gd0.01Mo0.03O2 catalyst had high stability during reuse. The high photocatalytic activity of the Ti0.96Gd0.01Mo0.03O2 catalyst was correlated to the broad visible-light absorption and effective separation of electron-hole pairs by Gd3+ and Mo6+ cations. The gas sensing characteristic is reflected by the high sensitivity of the Ti0.96Gd0.01Nb0.03O2 sensor to ethanol gas in the presence of different gases at 275 °C. The obtained results indicated that the (Gd, Mo) mixture could more effectively induce the photocatalytic properties of TiO2 while (Gd, Nb) dopants were the best for reinforcing its sensing characteristics.

Advances in Noble Metal-Decorated Metal Oxide Nanomaterials for Chemiresistive Gas Sensors: Overview

Highly sensitive gas sensors with remarkably low detection limits are attractive for diverse practical application fields including real-time environmental monitoring, exhaled breath diagnosis, and food freshness analysis. Among various chemiresistive sensing materials, noble metal-decorated semiconducting metal oxides (SMOs) have currently aroused extensive attention by virtue of the unique electronic and catalytic properties of noble metals. This review highlights the research progress on the designs and applications of different noble metal-decorated SMOs with diverse nanostructures (e.g., nanoparticles, nanowires, nanorods, nanosheets, nanoflowers, and microspheres) for high-performance gas sensors with higher response, faster response/recovery speed, lower operating temperature, and ultra-low detection limits. The key topics include Pt, Pd, Au, other noble metals (e.g., Ag, Ru, and Rh.), and bimetals-decorated SMOs containing ZnO, SnO2, WO3, other SMOs (e.g., In2O3, Fe2O3, and CuO), and heterostructured SMOs. In addition to conventional devices, the innovative applications like photo-assisted room temperature gas sensors and mechanically flexible smart wearable devices are also discussed. Moreover, the relevant mechanisms for the sensing performance improvement caused by noble metal decoration, including the electronic sensitization effect and the chemical sensitization effect, have also been summarized in detail. Finally, major challenges and future perspectives towards noble metal-decorated SMOs-based chemiresistive gas sensors are proposed.

Advances in functional guest materials for resistive gas sensors

Resistive gas sensors are considered promising candidates for gas detection, benefiting from their small size, ease of fabrication and operation convenience. The development history, performance index, device type and common host materials (metal oxide semiconductors, conductive polymers, carbon-based materials and transition metal dichalcogenides) of resistive gas sensors are firstly reviewed. This review systematically summarizes the functions, functional mechanisms, features and applications of seven kinds of guest materials (noble metals, metal heteroatoms, metal oxides, metal-organic frameworks, transition metal dichalcogenides, polymers, and multiple guest materials) used for the modification and optimization of the host materials. The introduction of guest materials enables synergistic effects and complementary advantages, introduces catalytic sites, constructs heterojunctions, promotes charge transfer, improves carrier transport, or introduces protective/sieving/enrichment layers, thereby effectively improving the sensitivity, selectivity and stability of the gas sensors. The perspectives and challenges regarding the host-guest hybrid materials-based gas sensors are also discussed.