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 H-2 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 (lambda <= 650 nm) compared to pure STO (lambda <= 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 H-2. The amounts of CH4 and CO produced over B, F-STO are similar to 17.2 and 21 mu mol, respectively, about 5-fold enhanced compared to that of STO (similar to 3.4 mu mol CH4 and 5.2 mu mol CO), and the calculated quantum efficiency at lambda = 420 nm is similar to 2.16%. Similarly, the amount of H-2 produced over B, F-STO is similar to 61 mu mol, about 6.7-fold enhanced compared to that over STO (9 mu mol), and the calculated quantum efficiency at lambda = 420 nm is similar to 2.12%. This work provides feasible routes to fabricate highly efficient SrTiO3-based nanophotocatalysts for solar-fuel production.