Harnessing of low-energy IR photons via oxygen-vacancies in SrTiO3 nanocrystals for photocatalytic hydrogen production

The surface-oxygen vacancies were generated to enhance the near-IR light response of the SrTiO3 photocatalyst by heating SrTiO3 in a highly reducing environment. The UV–visible diffuse reflectance spectra of SrTiO3-Ov revealed strong absorption between 400 and 800 nm, while IPCE response was extended beyond 800 nm, confirming the near-IR light response of SrTiO3-Ov. The hydrogen production rates for SrTiO3-Ov at pH 3.0 under full solar spectrum, visible and IR radiation were 100, 25 and 10 μlg−1h−1, respectively. The respective normalized hydrogen with respect to light intensity were found to be 100, 50 and 33 μlg−1h−1 while hydrogen production of pristine SrTiO3 was less than 2 μlg−1h−1 under full solar spectrum. The mid-gap Ov and Ti3+ states in SrTiO3-Ov are key factors in the origin of the near-IR responses of the catalyst and the feasibility of using low-photonic-energy IR light to produce hydrogen by water splitting was demonstrated.