The precise decoration of bimetallic nanocrystals (NCs) with uniform size and homogeneous composition on metal oxide (MOX) surfaces is crucial for developing highly sensitive and selective MOX-based gas sensors. In this study, MOX-based gas sensors are present decorated with homogeneous Au-Pd bimetallic (Au@Pd) NCs synthesized via seed-mediated sequential reduction of Au and Pd on an array of TiO2 nanohelices (NHs) matrix. Due to the uniform composition, size, and dispersion of the bimetallic NCs, the sensor exhibits outstanding toluene (C7H8) sensing performance. The optimized Au@Pd NC composition (Au:Pd = 55:45) facilitates chemisorbed oxygen spillover and electronic sensitization, achieving an exceptionally high response (Ra/Rg) of ≈130 000 and rapid response/recovery (69 s/4 s) toward 100 ppm of C7H8 at 200 °C. Furthermore, the homogeneity of Au@Pd NCs enhances selectivity by providing controlled active sites, yielding a 1008-fold higher response to toluene compared to acetone. Density functional theory calculations and mechanistic experiments reveal that Au@Pd NCs generate toluene-selective catalytic sites that enable complete oxidation. The findings demonstrate that homogeneous core-shell bimetallic NCs can be uniformly integrated on a highly porous MOXs-based gas sensing matrix, enabling exceptional selectivity and sensitivity for advanced gas sensor applications.
Keywords: bimetallic nanocatalyst; density functional theory; homogeneous decoration; titanium dioxide; toluene gas sensor.
© 2025 The Author(s). Small published by Wiley‐VCH GmbH.