Singular room-temperature hydrogen sensing characteristics with ultrafast recovery of PtNb2O5 porous composite ceramics

PtNb2O5 porous composite ceramics have been prepared from Pt and Nb2O5 particles through convenient pressing and sintering. Extraordinary room-temperature hydrogen sensing capabilities have been revealed for PtNb2O5 composite ceramics of 1 wt% Pt, including a sensitivity over 165, response time and recovery time of 7s and 39s, respectively, for 1% H2 in air. For 0.25% and lower concentrations of H2 in air, ultrafast recoveries, such as a recovery time of 8s for 0.04% H2 in air, are observed, which are singular for room-temperature hydrogen sensing. We further found a strong correlation between the resistance of PtNb2O5 composite ceramics and hydrogen concentration in ambient oxygen-free atmospheres, and a negative temperature dependence of hydrogen sensitivity, from which a hydrogen sensing mechanism rooted in hydrogen chemisorption on Nb2O5 has been established, while the ultrafast recoveries are explained in terms of a highly mobile and reactive state of chemisorbed hydrogen ions on Nb2O5.