Role of surface composition upon the photocatalytic hydrogen production of Cr-doped and La/Cr-codoped SrTiO₃

Surface properties play a vital role in many heterogeneous catalytic reactions, particularly in photocatalytic water splitting, where photo-generated electron and holes must migrate to and be transferred at the very top surface of a photocatalyst. Here, we carried out a detailed investigation on the role of surface composition towards photocatalytic hydrogen production of perovskite-based materials, namely, Cr-doped and La/Cr-codoped SrTiO₃. Our findings showed that a depletion of B site cations occurred at the surface of these high-temperature annealed samples and a severe diminishing of B site cations took place after introducing La cations at the A site. Although the presence of La helps to improve surface alkalinity and inhibit the formation of detrimental Cr⁶⁺ species, La/Cr-codoped sample showed a poor photocatalytic activity. Such a correlation between surface composition and photocatalytic activity suggests that surface tailoring or composition control is highly necessary in the design and development of these perovskite-based photocatalysts. Since surface rearrangements can be kinetically hindered at low temperatures, low temperature synthetic methods are therefore strongly preferred during the synthesis of these perovskite-based photocatalysts.