## 4 Conclusions  
In this work, photocatalysts based on g-C\({}_{3}\)N\({}_{4}\) modified with Pt and PtO were synthesized and studied in H\({}_{2}\) evolution from ethanol solution under visible light irradiation. Characterization of the photocatalysts using a set of research methods showed that photodeposition from H\({}_{2}\)PtCl\({}_{6}\) solution leads to a uniform distribution of platinum oxide particles over the surface of g-C\({}_{3}\)N\({}_{4}\). The use of NaBH\({}_{4}\) solutions for reduction makes it possible to deposit particles of metal platinum on the surface of g-C\({}_{3}\)N\({}_{4}\), which, despite their uneven distribution, lead to a higher rate of H\({}_{2}\) formation than platinum oxide. An increase in the metallic platinum content leads to a gradual decrease in carbon dioxide and a significant increase in methane in the gas phase. As the PtO loading increases, the amount of carbon dioxide grows, and a large amount of ethane is produced, which on the whole results in a decrease in the relative carbon dioxide content as the platinum oxide content increases. Thus, both the state of platinum and its content affect not only the rate of hydrogen formation, but also the rate of the formation of the reaction by-products, which confirms the need to control the selectivity of the hydrogen formation process from organic electron donors.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app132111739/s1](https://www.mdpi.com/article/10.3390/app132111739/s1)]([https://www.mdpi.com/article/10.3390/app132111739/s1](https://www.mdpi.com/article/10.3390/app132111739/s1)), Figure S1: XRD patterns of (a) 5% Pt/g-C\({}_{3}\)N\({}_{4}\) and (b) 5% Pt/g-C\({}_{3}\)N\({}_{4}\); Figure S2: Tauc plot of unmodified g-C\({}_{3}\)N\({}_{4}\).  
Investigation, data curation, visualization, writing--original draft preparation, A.Y.K.; investigation, data curation, visualization, writing--review and editing, funding acquisition, project administration, A.A.S.; investigation, data curation, D.D.M.; investigation, data curation, E.Y.G.; writing--review and editing, supervision, conceptualization, E.A.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2022-263).  
Investigational Review Board Statement: Not applicable.  
Informed Consent Statement: Not applicable.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Photocatalyst** & **Light Source** & **C\({}_{0}\)(ethanol)** & **W(H\({}_{2}\)), mmol h\({}^{-1}\) g\({}_{cat}\)\({}^{-1}\)** & **S(H\({}_{2}\)), \%** & **Reference** \\ \hline Pt/TiO\({}_{2}\) & Hg lamp & 25\% & 84.6 mmol after 4 h & 93.8 & [45] \\
0.29\% Pt/TiO\({}_{2}\) & 380-nm LED & 10\% & 5.3 & - & [51] \\
0.20\% Pt/CdS & AM1.5G & neat ethanol & 11.5 & - & [65] \\
3\% Pt/UCN/Nb\({}_{2}\)O\({}_{5}\) & AM1.5G & neat ethanol & 0.56 & - & [66] \\ Pt-Ag/Ag\({}_{3}\)PO\({}_{4}\)-WO\({}_{3}\) & Xe lamp & 20\% & 4.0 mmol after 12 h & & [67] \\
0.5\% Pt/g-C\({}_{3}\)N\({}_{4}\) & 409-nm LED & 20\% & 0.6 & 98.9 & Present study \\ \hline \end{tabular}
\end{table}
Table 3: Comparison of the activity and selectivity of the synthesized photocatalysts with literature data.