Decorating Thermodynamically Stable (101) Facets of TiO₂ with MoO₃ for Multifunctional Sustainable Hydrogen Energy and Ammonia Gas Sensing Applications

The simultaneous realization of sustainable energy and gas sensors dealing with the emission of pollutants is indispensable as the former thrives on the minimization of the latter. However, there is a dearth of multifunctional nanocatalysts in the literature. This ascertains the importance of multifunctional semiconductors which can be utilized in H₂ generation via overall water splitting and in the gas sensing of global pollutants such as NH₃. MoO₃-decorated TiO₂ Z-scheme heterostructures exceptionally escalate the photochemical and photo/electrochemical H₂ evolution performance and gas sensing response of TiO₂ owing to the synergistic relationship between TiO₂ and MoO₃. Extensive structural, morphological, and optical characterizations, theoretical studies, and XPS results were exploited to develop a mechanistic framework of photochemical H₂ evolution. The photochemical response of the optimum TiO₂-MoO₃ composition (20 wt % MoO₃-TiO₂) was found to be nearly 12- and 20-fold superior to the pristine TiO₂ and MoO₃ photocatalysts, respectively, with the remarkable H₂ evolution rate of 9.18 mmol/g/h and AQY of 36.02%. In addition, 20 wt % MoO₃-TiO₂ also showed advanced photo/electrochemical efficiency with 0.61/0.7 V overpotential values toward HER due to the higher electrochemically active surface area and Tafel slope as low as 65 mV/dec. The gas sensing response of 20 wt % MoO₃-TiO₂ toward NH₃ gas turned out to be 2.5-fold higher than that of the pristine TiO₂ gas sensor.