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

Abstract

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 H 2 generation via overall water splitting and in the gas sensing of global pollutants such as NH 3 . MoO 3 -decorated TiO 2 Z-scheme heterostructures exceptionally escalate the photochemical and photo/electrochemical H 2 evolution performance and gas sensing response of TiO 2 owing to the synergistic relationship between TiO 2 and MoO 3 . Extensive structural, morphological, and optical characterizations, theoretical studies, and XPS results were exploited to develop a mechanistic framework of photochemical H 2 evolution. The photochemical response of the optimum TiO 2 −MoO 3 composition (20 wt % MoO 3 −TiO 2 ) was found to be nearly 12-and 20-fold superior to the pristine TiO 2 and MoO 3 photocatalysts, respectively, with the remarkable H 2 evolution rate of 9.18 mmol/g/h and AQY of 36.02%. In addition, 20 wt % MoO 3 −TiO 2 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 % MoO 3 −TiO 2 toward NH 3 gas turned out to be 2.5fold higher than that of the pristine TiO 2 gas sensor.

Enhanced Photo/Electrocatalytic Hydrogen Evolution by Hydrothermally Derived Cu-Doped TiO2 Solid Solution Nanostructures

“…In Figure b–d, the 2.5% Cu-doped TiO 2 spectrum displays two peaks in the Ti 2p high-resolution spectrum at 458.3 and 464.0 eV, corresponding to Ti 2p 3/2 and Ti 2p 1/2 valence states, and the Cu 2p peaks around 933.0 are indicative of Cu + or metallic Cu, while the distinctive peaks at 934.0, 945.36, 951.8, and 958.4 eV correspond to Cu 2+ . , The 5.7 eV splitting between the Ti 2p 3/2 and Ti 2p 1/2 peaks indicates the presence of Ti 4+ in 2.5% Cu-doped TiO 2 . The O 1s spectrum shows a distinct peak of Ti–O bond (oxygen vacancy related Ti 3+ and Ti 4+ ) at 529.7 eV. ,, To assess the relative intensity of TiO 2 and 2.5% Cu-doped TiO 2 , the Ti 2p spectrum in Figure e reveals a slight negative shift of 0.7 eV in the Ti 2p 3/2 peak, suggesting an increase in electron density in 2.5% Cu-doped TiO 2 due to Cu doping. , Additionally, changes in the oxygen peak suggest the presence of oxygen vacancies, supporting their existence. This shift indicates the tunneling of photocharged carriers between Cu and TiO 2 , enhancing the catalytic performance of 2.5% Cu-doped TiO 2 for HER.…”

Hydrogen Energy as Sustainable Energy Resource for Carbon-Neutrality Realization

“…Conversely, there are number of renewable energy resources for green H 2 production such as solar, wind, hydropower, nuclear, biomass, and geothermal . Amidst the renewable resources which are contemplated to produce H 2 , solar and wind energies are consistently utilized for H 2 production to date. , Overall, water splitting, primarily known for photocatalytic, electrocatalytic, and photoelectrocatalytic water splitting using advanced materials, − is considered as the most felicitous method for green H 2 generation or through dehydrogenation of molecules containing H 2 . The world’s biggest green H 2 plant has been proposed to be constructed in 2025 with a capability to operate 650 ton/day H 2 generation by utilizing electrolysis and 4 GW renewable energy from wind, solar, and storage. , Although, there are few technological obstacles conquered to make this technique achievable from both economic and engineering aspects.…”

Photoinduced Hole Trapping in MoSe2–MoS2 Nanoflowers/ZnO Nanosheets S-Scheme Conduit for Ultrafast Charge Transfer during Hydrogen Evolution

“…Hitherto, for large-scale H 2 production, noble metals such as Pt or Pd have been exploited . But their extortionate cost and scarcity have motivated researchers to look beyond them and design binary/ternary heterostructured catalytic systems. , Noble metal-free, cost-effective OWS operations demand the fabrication of a highly efficient multicomponent catalytic system consisting of end-to-end heterojunctions as the interfaces ease out the separation of photocharged carriers and enhance its transport properties, which trigger the rate of H 2 evolution . In addition, the catalytic system should have a high specific surface area, superficial scalability, and robust stability.…”