# Photocatalytic Activity of TiNbC-Modified TiO2 during Hydrogen Evolution and CO2 Reduction
## 4 Conclusions  
Note that we have carried out photocatalytic tests on photocatalytic hydrogen evolutions and CO\({}_{2}\) reductions using the heterostructures based on TiO\({}_{2}\) and MXenes Mo\({}_{2}\)Ti\({}_{2}\), Mo\({}_{2}\)Ti\({}_{2}\)C\({}_{3}\), VCrC, and TiNbc with MXene contents of 1, 5, and 10% as photocatalysts. Only the TiNbc/TiO\({}_{2}\) heterostructures showed photocatalytic activities.  
Figure 7: Kinetics of methane formation depending on the TiNbc content (**a**); TiNbc/TiO\({}_{2}\) photocatalyst activity (**b**); and product formation rate depending on the TiNbc content (**c**).  
The study of the photocatalytic activities of TiNbC/TiO\({}_{2}\) in the processes of hydrogen evolution and reduction of CO\({}_{2}\) demonstrated for the first time that the creation of heterostructures of MXene and titanium dioxide can be considered a promising way to create new materials for the needs of green energy. It was also shown that there was an area of an optimal ratio between the components of a heterostructure in the creation of such heterostructures. In the case considered in this article, the optimal ratio was the addition of 5% MXene to titanium dioxide. The question remains open about the promising use of this heterostructure in the form of nanoparticles. But, for this purpose, it is necessary to work out the technology of the synthesis of such nanoparticles. From the general physical concepts, heterostructures in the forms of nanoparticles should be more active in photocatalytic processes.  
In a recent work, the photocatalytic activities of TiO\({}_{2}\)/Ti\({}_{3}\)C\({}_{2}\) nanocomposites with MXene contents of Ti\({}_{3}\)C\({}_{2}\) \(<\) 10%, 38.7%, and 96% were investigated on fabrication methods for MXene-based photocatalysts and photocatalytic performances for contaminant degradation, CO\({}_{2}\) reduction, H\({}_{2}\) evolution, and N\({}_{2}\) fixation with various MXene-based nanocomposites [39]. The use of compounds such as TiO\({}_{2}\), BiVO\({}_{4}\), Ag\({}_{3}\)PO\({}_{4}\), In\({}_{2}\)S\({}_{3}\), CdS, BiFeO\({}_{3}\), BiOBr, Fe\({}_{2}\)O\({}_{3}\), RuO\({}_{2}\), C\({}_{3}\)N\({}_{4}\), AgInS, and MIL-100(Fe) as co-catalysts remains a promising direction.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13169410/s1](https://www.mdpi.com/article/10.3390/app13169410/s1)]([https://www.mdpi.com/article/10.3390/app13169410/s1](https://www.mdpi.com/article/10.3390/app13169410/s1)), Figure S1: EDS analysis of the heterostructures TiNbC/TiO\({}_{2}\) with concentrations 1, 5, and 10% TiNbC. Figure S2: The element distribution map on a typical 5% TiNbC/TiO\({}_{2}\) particle. Figure S3: Typical image of TiNbC/TiO\({}_{2}\) heterostructure.  
A.V.S. ([PERSON]), D.S.S., E.A.K., A.A. and V.V.: Conceptual (equal); Data curation (equal); Formal analysis (equal); Investigation (equal); Methodology (equal); Validation (equal); Visualization (equal); Writing--original draft (equal); Writing--review and editing (equal). M.S.G., G.I.T., A.Y.K., A.V.Z., A.V.S. ([PERSON]) and G.V.T.: Funding acquisition (equal); Investigation (supporting); Methodology (equal); Validation (equal). All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Russian Science Foundation, project No. 22-19-00094.  
Not applicable.  
TEM analysis was performed using the equipment of the Center of Shared Research Facilities (MIPT).  
The authors declare no conflict of interest.