Interactions of Oxygen Vacancies with Photoinduced {Hole/Electron} Pairs in SrTiO<sub>3–<i>x</i></sub>: Their Key Role in Photocatalytic H<sub>2</sub> Production
Areti Zindrou, Loukas Belles, Yiannis Deligiannakis
Abstract
High Resolution Image Download MS PowerPoint Slide 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.