# Recent Advances and Applications of Semiconductor Photocatalytic Technology
## 6 Application  
### Photocatalytic Hydrogen Production  
In recent decades, the use of petroleum and coal resources has been increasing, and the number of unrepairable resources on Earth is getting fewer and fewer. Furthermore, combustion of fossil fuels has \begin{table}
\begin{tabular}{c c c} \hline \hline
**Modification Method** & **Advantage** & **Disadvantage** \\ \hline \multirow{2}{*}{Particle doping} & - Reduce bandgap & - Introduce defects \\  & - Reduce particle size & - Extensive \\ \hline \multirow{2}{*}{Precious metal depositing} & - Enhance electron-hole separation & - Expensive \\  & - Broaden the light response range & - Expensive \\  & - Broaden the light response range & - Dyes may be photolyzed \\ \hline \multirow{2}{*}{Semiconductor compound} & - Reducing the complex of electron-hole pairs & - Energy loss \\  & - Broaden the light response range & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Advantages and disadvantages of different modification methods for semiconductor. caused many environmental problems that have significantly influenced the development of science and technology, as well as the daily life of humans. Hydrogen is considered the most promising clean energy source of the 21 st century. Hydrogen is characterized by being odorless, non-toxic, environmentally friendly, and capable of producing a large amount of energy. Hydrogen energy is a secondary energy source and needs to be prepared from other hydrogen-containing substances such as water and fossil fuels. There are a variety of ways of producing hydrogen, and the most common way is to decompose fossil fuels to produce hydrogen. However, this method relies on fossil fuels in the final analysis. The photocatalytic degradation of water to produce hydrogen to achieve the conversion of solar energy to hydrogen energy is an effective method to solve energy and environmental problems. The photocatalytic decomposition of water to generate hydrogen can convert solar energy into hydrogen energy, which is an effective method to solve energy and environmental problems. Since the first photocatalytic decomposition of water to produce hydrogen in 1972, researchers have used powdered semiconductor materials to achieve the photocatalytic decomposition of water to produce hydrogen [7; 2157 -220]. Photocatalytic hydrogen production not only achieves the use of solar energy but also reduces environmental problems caused by energy use. Therefore, photocatalytic technology is considered to be the most ideal and cleanest way to produce and utilize energy [333; 334]. Monoaatomic catalysts can reduce costs by reducing the amount of precious metals used, but the challenge is how to maintain catalyst stability. [PERSON] et al. synthesized a bimetallic MXene nanosheet Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\)[335]. A large amount of Mo vacancies formed in the outer layer of the Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\), and after the Pt atoms were fixed in these vacancies, the hydrogen generation effectiveness of the Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\) was greatly improved, as shown in Figure 8B. The hydrogen evolution catalytic activity of the catalyst reached a current density of 100 mA/cm\({}^{2}\), requiring only an overpotential of 77 mV. Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\) has a 40-fold increase in mass activity compared to the commercially available platinum-carbon catalyst. Studies have shown that the superior catalytic performance and stability of Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\) arises from the covalent effect of Pt and MXene. As shown in Figure 8A, Mo\({}_{2}\)TiC\({}_{2}\)T\({}_{\rm x}\)-PtSA showed the best performance in all samples. [PERSON] et al. [336] synthesized g-C\({}_{3}\)N\({}_{4}\) combined with PtNi\({}_{\rm x}\). As shown in Figure 9A, the PtNi\({}_{\rm x}\)/g-C\({}_{3}\)N\({}_{4}\) composites with different mass ratios have higher photocatalytic activities than pure g-C\({}_{3}\)N\({}_{4}\).