Synergistic PdAg bimetallic nanoparticles on WO3 nanocubes enabled by tannic acid for enhanced hydrogen response and kinetics

The practical application of chemiresistive hydrogen (H 2 ) sensors based on WO 3 is frequently hampered by high operating temperatures and limited response amplitudes. Herein, a high-performance H 2 sensor was present based on PdAg bimetallic nanoparticle-modified WO 3 nanocubes. The WO 3 nanocubes were synthesized via hydrothermal treatment and subsequently functionalized with uniformly dispersed PdAg nanoparticles using a tannic acid (TA)/ascorbic acid (AA)-mediated reduction-precipitation approach. Density functional theory (DFT) calculations confirm that the PdAg bimetallic system optimizes WO 3 ’s electronic structure, achieving a more negative H 2 adsorption energy (-0.67 eV) than pristine WO 3 (-0.07 eV) and Pd/WO 3 (-0.49 eV), which strengthens H 2 activation. The optimized 0.10 at% PdAg 0.50 -WO 3 sensor demonstrates exceptional performance, operating at 185 °C (a significant reduction of 30 °C compared to pure WO 3 -based sensors) and exhibiting an ultrahigh response (R a /R g = 4348 at 500 ppm H 2 ). Furthermore, this sensor features rapid response/recovery times (1 s/16 s), a low detection limit of 1 ppmH 2 , and negligible reactivity toward common volatile organic compounds (e.g., ethanol, acetone) and inorganic interferents (e.g., CO, CH 4 ). These superior sensing properties are attributed to the synergistic effects of the PdAg/WO 3 Schottky junctions, the enhanced catalytic activity of bimetallic sites for H 2 dissociation and O 2 activation, and the abundant oxygen vacancies that facilitate surface reactions.