A stable room-temperature chemiresistive H2 gas sensor can restore itself to its initial state after being covered with H2O via refreshing its surface

Until now, no one hydrogen sensing technology can meet all requirements of application. Hydrogen sensors working in extreme conditions are needed. Chemiresistive gas sensors own lots of merits but suffer from high relative humidity (RH). Furthermore, if its surface is covered with H${}_2$O, the sensor must be abandoned as it cannot work again. Here, a chemiresistive H${}_2$ gas sensor based on Pt-WO${}_3$ composite dense film which can restore itself to its initial state after being covered with H${}_2$O has been fabricated. The restoring is realized by first blow-drying then annealing. The H${}_2$O-covering–restoring circulation can last 10 times at least. Towards 50 ppm H${}_2$, its response value decreases only 25% from RH=40% to 90% (RH set and measured at 25 °C ) at 120 °C. Working at 25 °C, its detection limit is 10 ppm. The sensor also exhibits good response repeatability, long-term stability (1 year at least), selectivity and batch-to-batch reproducibility. The strong restoring ability of the sensor can be ascribed to the easy desorption character of H${}_2$O from the surface of WO${}_3$ and its dense-film structure, which makes the sensor afford many times of annealing, but do not produce cracks.