Aerosol-Assisted CVD-Grown PdO Nanoparticle-Decorated Tungsten Oxide Nanoneedles Extremely Sensitive and Selective to Hydrogen

We
report for the first time the successful synthesis of palladium (Pd)
nanoparticle (NP)-decorated tungsten trioxide (WO3) nanoneedles
(NNs) via a two-step aerosol-assisted chemical vapor deposition approach.
Morphological, structural, and elemental composition analysis revealed
that a Pd­(acac)2 precursor was very suitable to decorate
WO3 NNs with uniform and well-dispersed PdO NPs. Gas-sensing
results revealed that decoration with PdO NPs led to an ultrasensitive
and selective hydrogen (H2) gas sensor (sensor response
peaks at 1670 at 500 ppm of H2) with low operating temperature
(150 °C). The response of decorated NNs is 755 times higher than
that of bare WO3 NNs. Additionally, at a temperature near
that of the ambient temperature (50 °C), the response of this
sensor toward the same concentration of H2 was 23, which
is higher than that of some promising sensors reported in the literature.
Finally, humidity measurements showed that PdO/WO3 sensors
displayed low-cross-sensitivity toward water vapor, compared to bare
WO3 sensors. The addition of PdO NPs helps to minimize
the effect of ambient humidity on the sensor response.