“…[3,26,28] Thus, the lower limit of detection and sensitivity were improved by the use of nanostructured materials with grain sizes comparable to twice their Debye length. [29][30][31][32] Finely dispersing catalyst nanoparticles, such as Pt, [33][34][35] Pd, [33,36,37] Ag, [38,39] Ru, [40] and Au [41,42] on the metal oxide surface, further increased the sensitivity, mainly by spillover effects. Nevertheless, the long-term stability at the operating temperature (typically 250-600 8C) of these highly sensitive materials composed of oxide [30,32,43] and dopant [41,44] components is still challenging.…”