Fabrication and characterization of thermochemical hydrogen sensor with laminated structure

In this study, we reported the simple and cost-effective fabrication of thermochemical hydrogen (TCH) sensors composed of chalcogenide thin films and Pt/Al₂O₃powders. Chalcogenide thin films of two types, composed of Bi₂Te₃(monomorphic-type) and Bi₂Te₃—Sb₂Te₃(four-leg PN junction-type), were prepared by electrochemical deposition. The Pt/Al₂O₃powder, which acts as a heating catalyst, was synthesized by impregnation of an Al₂O₃powder with an aqueous solution of platinum (IV) chloride pentahydrate. Its heating process was optimized via a hydrogen-sensing evaluation to control the size of the Pt particles. The monomorphic-type TCH sensor showed an output signal of 14.2 μV in response to 10 vol% hydrogen gas, whereas an output signal of 39.6 μV was obtained from a four-leg PN junction–type TCH sensor. Even though the n–p junction-type had the same deposition area as that of the monomorphic-type, the output signal of the n–p junction TCH sensor was greater by a factor of 2.8. In addition, the monomorphic-type TCH sensor had an inferior response time (T₉₀) of 31 s and a longer recovery time (D₁₀) of 38 s; the four-leg PN junction-type TCH sensor had a lowest response time of 27 s and a fastest recovery time of 9 s (in 3% H₂/air at room temperature).