Abstract
The present work elucidates the role of lattice oxygen vacancies (V(o)s) in SrTiO(3) (STO) nanoparticles on the spin dynamics of photogenerated charge carriers (electrons/holes, e(-)/h(+)) and on the photocatalytic hydrogen (H(2)) evolution from H(2)O. V(o)-enriched STO materials (V(o)-STO) were synthesized via anoxic flame spray pyrolysis (A-FSP) technology that allowed production of a library of SrTiO(3-x) nanomaterials with controlled V(o) concentrations. The optimal V(o)-STO materials exhibited a 200% increase in photocatalytic H(2) production rates compared with pristine STO. A combined study using electron paramagnetic resonance spectroscopy and photoelectrochemistry reveals that monomeric oxygen vacancies (type-B V(o)s) are the key factors to boost photoinduced charge separation via suppression of the e(-)/h(+) recombination. Mott-Schottky and electrochemical impedance spectroscopy show that increased surface V(o) population results in a slight upshift of flat band potential (E (fb)) and decreases the interfacial charge-transfer resistance, hence enhancing photocatalytic activity. Furthermore, open-circuit potential decay measurements reveal longer e(-)/h(+) carrier lifetimes in V(o)-rich SrTiO(3-x) . The present findings highlight the potential of V(o)-spin engineering toward fine-tuning the electronic properties and photocatalytic activity of perovskite oxides. Technology wise, the present study exemplifies A-FSP as a versatile, industrial scale technology for the synthesis of V(o)-enriched perovskite nanomaterials.