XU Hongyan，LI Gen

School of Materials Science and Engineering， University of Jinan， Jinan 250022， China

Abstract

Significance As an n-type semiconductor， WO₃ is widely used in the field of gas sensors due to its wide band gap， high thermal stability， and easy synthesis. Given the importance of monitoring hydrogen concentration in ensuring the safety of industrial production and daily life， it is crucial to develop gas sensors that achieve both rapid response and high sensitivity to hydrogen.

Progress WO₃ materials are known for their flexible structural properties， which can improve gas sensing performance through various approaches， such as noble metal catalysis and heterostructure construction. Doping WO₃ with noble metals such as palladium and platinum and constructing heterojunctions with other semiconductors are strategies that have been proved to significantly enhance hydrogen selectivity and sensitivity. This paper reviews the current research and future prospects of hydrogen sensors， focusing on four areas： preparation methods， morphological characteristics， gas-sensing performance， and mechanisms.Sensor materials are prepared using methods such as hydrothermal synthesis， sol-gel processes， radio frequency magnetron sputtering （RFMS）， and glancing angle deposition （GLAD）. These materials are then characterized using scanning electron microscopy （SEM）， transmission electron microscopy （TEM）， and X-ray diffraction （XRD）， and their gas-sensitive properties are evaluated using various instruments. Consequently， the underlying mechanisms are explained scientifically and precisely.

Conclusion and Prospects WO₃ is one of the most promising materials in the field of sensing technology and has become a focal point of research in recent years. This paper reviews the preparation methods of WO₃ nanomaterials and their composites， as well as the current research advancements in H₂ gas detection. The morphology of metal oxides has a significant impact on gas-sensing performance. The specific surface areas and exposed crystal surfaces of WO₃ vary with different morphologies， resulting in differences in contact areas and active sites for target gases. Thus， the preparation of WO₃ materials with distinct morphologies has become a crucial area of research. One of the most common methods for improving gas-sensing performance is the introduction of noble metal doping. This can be achieved through chemical and electronic sensitization， which enhances sensor response. The strong coupling effect between specific metals and certain gases also improves sensor selectivity and reduces operating temperature. The dissociation of hydrogen atoms by platinum at room temperature greatly reduces the operating temperature of the sensor. Also， doping palladium into tungsten trioxide， a semiconductor， significantly enhances hydrogen detection.Studies have demonstrated that compared to pure WO₃， palladium doping significantly improves hydrogen detection. Overall，the doping of noble metals and the construction of heterojunctions can reduce operating temperature， enhance sensitivity， reduce the detection limit， and shorten the recovery and response times， making these strategies highly effective compared to using onlypure phase WO₃ semiconductor materials.

Keywords：gas sensor； oxide semiconductor； tungsten trioxide