Exceptional co-catalyst free photocatalytic activities of B and Fe co-doped SrTiO₃ for CO₂ conversion and H₂ evolution

CO₂ should be converted into chemical-fuels, and to reduce H₂O to H₂ over SrTiO₃ (STO) owing to its negative conduction band position vs. NHE. Herein a novel B and Fe co-doped SrTiO₃ (B, F-STO) photocatalyst was successfully fabricated via a single-step sol-hydrothermal process. Various experiments confirmed that B and Fe are effectively doped into the STO matrix. Boron substituted oxygen anions, while Fe substituted Ti cations. UV–visible diffuse reflectance spectra (UV–vis DRS) and valence-band X-ray photoelectron spectroscopy (XPS) spectra confirmed that the band gap of STO significantly reduced from 3.4 to 1.9 eV upon co-doping with B and Fe. Hence, the B, F-STO photocatalyst exhibits more absorption (λ ≤ 650 nm) compared to pure STO (λ ≤ 360 nm). Further, from photoluminescence spectra, fluorescence spectra, and photoelectrochemical measurements, charge separation in STO is considerably enhanced by co-doping B and Fe. This resulted in the improved UV–vis light catalytic activities for CO₂ conversion to CH₄ and CO and H₂O splitting to evolve H₂. The amounts of CH₄ and CO produced over B, F-STO are ~ 17.2 and 21 μmol, respectively, about 5-fold enhanced compared to that of STO (~ 3.4 μmol CH₄ and 5.2 μmol CO), and the calculated quantum efficiency at λ = 420 nm is ~ 2.16%. Similarly, the amount of H₂ produced over B, F-STO is ~ 61 μmol, about 6.7-fold enhanced compared to that over STO (9 μmol), and the calculated quantum efficiency at λ = 420 nm is ~ 2.12%. This work provides feasible routes to fabricate highly efficient SrTiO₃-based nanophotocatalysts for solar-fuel production.