**4. Conclusions**

One-dimensional photocatalysts based on SrTiO3/PAN fibers with the addition of metal oxide particles were obtained by the electrospinning method. A study of the transmission and reflection spectra showed that the addition of Cr2O3, CuO, and Fe2O3 particles led to decreases in the bandgaps of SrTiO3/PAN-based photocatalysts to 2.89, 2.84, and 3.11 eV, respectively. As a result of the addition of metal oxide particles to the initial SrTiO3/PAN-based photocatalyst, the rate of hydrogen evolution in the photocatalytic splitting of a water–methanol mixture increased to 344.67 μmol h−<sup>1</sup> g<sup>−</sup><sup>1</sup> for the photocatalyst based on SrTiO3/PAN/Fe2O3, 398.93 μmol h−<sup>1</sup> g<sup>−</sup><sup>1</sup> for the photocatalyst based on SrTiO3/PAN/Cr2O3, and 420.82 μmol h−<sup>1</sup> g<sup>−</sup><sup>1</sup> for the photocatalyst based on SrTiO3/PAN/CuO. We believe that this article's proposed approach for increasing the efficiency of photocatalysts by the addition of non-expensive materials, allowing for a reduction in their bandgap, is a promising method for the further development of technologies for efficient solar hydrogen production.

**Author Contributions:** Conceptualization: F.S. and S.A.; validation and formal analysis: K.B.; investigation: C.D. and B.B.; writing—original draft preparation: F.S. and C.D.; writing—review and editing: M.B. and Z.M.; project administration: K.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Ministry of Education and Science of the Republic of Kazakhstan in the framework of the scientific and technology Program BR05236795 "Development of Hydrogen Energy Technologies in the Republic of Kazakhstan".

**Acknowledgments:** Seitkhan Azat is grateful to al-Farabi Kazakh National University for financial support in the frame of the «Best University teacher—2019 gran<sup>t</sup> MES RK».

**Conflicts of Interest:** The authors declare no conflict of interest.
