Improved room-temperature hydrogen sensing performance of directly formed Pd/WO3 nanocomposite

• Shape-controlled synthesis of palladium nanocubes on WO3 nanoplates is achieved by a facile solvothermal method.
• The micro-fabricated sensor exhibits fast, high and reversible response toward hydrogen at room temperature.
• The directly formed nanocomposite shows much better sensing performance than the mechanically mixed one.
• Seeking methods to form robust contact between Pd nanocrystals and metal oxides is a promising strategy to improve the sensing performance.

The fast-growing hydrogen economy creates a high demand for fast and safe hydrogen detecting techniques. Nanocomposites based on palladium (Pd) loaded metal oxides have been widely used to meet this requirement. However, the relationship between how the Pd nanocrystals and metal oxides are joined together and the sensing performance has not been rigorously studied. We report the shape-controlled synthesis of Pd nanocubes on WO3 nanoplates by a solvothermal method. Room-temperature hydrogen sensors based on the Pd/WO3 nanocomposite are demonstrated with high and fast response. A detection limit of 0.05 vol% is achieved with a response of 21. The response time of this sensor decreases with increasing gas concentrations and becomes less than 10 s as the concentration exceeds 1 vol%. In addition, the hydrogen sensing characteristics of this nanocomposite have been compared with that of pure WO3 and mechanically mixed Pd nanocubes and WO3 nanoplates. The significantly improved performance of the directly formed composite compared with the mechanically mixed one possessing the same Pd loading amount is discussed based on the spillover effect. In addition, this work indicates that seeking methods to form robust contact between Pd nanocrystals and metal oxides is a promising strategy to improve the sensing performance.

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