Synthesis Of Pt Or Pd Loaded WO₃ Composite Via Photodeposition And Study Of Its Gas Sensing Properties

It still remains considerable challenges in gas sensor applications for developing a suitable material with highly selective detection,rapid response,and superior sensitivity against specific target gases.Chemiresistive sensors,based on semiconducting metal oxides?SMOs?,have received much attention given their extensive applications in the monitoring of toxic and flammable gases,and medical diagnosis.Besides,atomically dispersed noble metal catalysts often exhibit high catalytic performances and combining them with semiconductor metal oxides?SMOs?can not inly enhance the sensitivity toward target gas,but reduce the amount of noble metals.Herein,we demonstrated a facile photodeposition route for in-situ synthesis of WO₃ loaded atomic-scale dispersed Pt or Pd composites.The synthesis mechanism of the atomic scale noble metal dispersed on the surface of WO₃ nanoplates?NPs?was discussed in detail.On the basis of electron depletion model,considering the catalytic and sensitization effect of noble metals,we also investigated the mechanism of superior gas sensitive performance.In this work,atomically dispersed Pt/WO₃ NPs composites were synthesized via in situ photodeposition method.The Pt species are stabilized by amorphous H₂WO₄ on the surface of WO₃ NPs.The as-prepared atomically dispersed Pt/WO₃ NPs composites exhibited excellent sensing performance.Its response of Pt/W-1-Xe to 30ppm butanone at 150°C was 92.45,which was about 9 times higher than pristine WO₃?R_a/R_g=10.94?,response and recovery time were 9 and 14 s,respectively.The detection limit of the fabricated sensors with Pt/WO₃ NPs composites was 2.08 for125 ppb butanone,and pristine WO₃ NPs showed a corresponding gas response of1.72.These results can be attributed to the remarkable atom efficiency of atomically dispersed Pt,leading to a maximized catalytic and sensitization effects distributed across the whole surface of the sensing layers.And it can provide more adsorption and active site to butanone gas,thus improving the gas sensing properties of materials.These results revealed that atomically dispersed Pt/WO₃ NPs composite is a potential candidate in exhaled gas detection and noninvasive monitoring of the human body health.On the basis of the experimental results,we synthesized Pd/WO₃ composites via in situ photodeposition method.Pd species were well dispersed on WO₃ nanoplates?NPs?and stabilized by amorphous H₂WO₄.It also exhibited excellent sensing performance.The response of Pd/W-1-UV to 30 ppm butanone at 150°C was 49.73,response and recovery time were 5 and 18 s,respectively.The superior gas sensing performance can be attributed to the catalysis and sensitization effects of well-dispersed Pd.It can provide more adsorption and active site to butanone and promote butanone spread to the entire surface.At the same time,when exposed to butanone,the electronic sensitization and chemical sensitization effect of Pd would thicken the electron depletion layer and lead to large change of Schottky barrier,therefore,achieved the high sensitivity and selectivity of butanone.