Hydrogen is largely
adopted in industrial processes and is one
of the leading options for storing renewable energy. Due to its high
explosivity, detection of H
2
has become essential for safety
in industries, storage, and transportation. This work aims to design
a sensing film for high-sensitivity H
2
detection. Chemoresistive
gas sensors have extensively been studied for H
2
monitoring
due to their good sensitivity and low cost. However, further research
and development are still needed for a reliable H
2
detection
at sub-ppm concentrations. Metal-oxide solid solutions represent a
valuable approach for tuning the sensing properties by modifying their
composition, morphology, and structure. The work started from a solid
solution of Sn and Ti oxides, which is known to exhibit high sensitivity
toward H
2
. Such a solid solution was empowered by the addition
of Nb, which—according to earlier studies on titania films—was
expected to inhibit grain growth at high temperatures, to reduce the
film resistance and to impact the sensor selectivity and sensitivity.
Powders were synthesized through the sol–gel technique by keeping
the Sn–Ti ratio constant at the optimal value for H
2
detection with different Nb concentrations (1.5–5 atom %).
Such solid solutions were thermally treated at 650 and 850 °C.
The sensor based on the solid solution calcined at 650 °C and
with the lowest content of Nb exhibited an extremely high sensitivity
toward H
2
, paving the way for H
2
ppb detection.
For comparison, the response to 50 ppm of H
2
was increased
6 times vs SnO
2
and twice that of (Sn,Ti)
x
O
2
.