### 1.1 Introduction  
Photoelectrochemistry is one of an important area of chemical science and uses the renewable resource of the sun to initiate a complex of chemical transformations required in industry and in everyday life. The main photoelectrochemical processes include the decomposition of water into molecular H\({}_{2}\) and O\({}_{2}\)[1; 2; 3], the reduction of CO\({}_{2}\) to the simplest organic compounds (artificial photosynthesis) [4; 5; 6; 7], and dye-sensitized solar cell cells [8; 9].  
A large number of photoactive semiconductor materials based on double or ternary oxides [10], sulfides [11], and phosphides [12] of transition metals exhibiting high activity in various photoelectrochemicals reactions have been studied and proposed. The mechanism of action of these photoactive semiconductor materials is as follows: by absorbing a photon in a photoactive semiconductor, an electron-hole pair (\(e^{-}\) and \(h^{+}\)) is generated, which, when it diffuses to the surface, can participate in a cycle of redox reactions on anodes and cathodes.  
A significant problem is the fact that wide-gap semiconductors (especially oxide semiconductors) have a low absorption coefficient in thin layers. This problem was solved by applying metal nanoparticles, such as Au, Ag, Cu, etc., to the semiconductor [13; 14; 15]. Metal nanoparticles have the effect of surface plasmon resonance, increasing the absorption coefficient of visible radiation by a semiconductor film increasing its photocatalytic and photoelectrochemical characteristics The material, morphology, and size of metal particles are key factors that determine the spectral region in which plasmon resonance will be observed [16] and, therefore, whether the absorption of visible radiation will increase. In the literature, the formation of a layer of metal nanoparticles using a physical and chemical approach is considered. As an example, we can cite the production of granular gold films by magnetron [17] and thermal [18] sputtering methods. The chemical approach to the deposition of gold nanoparticles is also diverse; standard methods of wet chemistry [19] and methods of photochemistry [20] have both been proposed. In our opinion, one of the most promising methods related to photochemistry is the method of laser-induced chemical liquid-phase deposition (LCLD) of metals from solution on the surface [21; 22]. This method was used to form gold nanoparticles on the oxide-modified surface. This technique is based on the photochemical reduction of a metal on the surface of a dielectric under the influence of laser radiation. LCLD method makes it possible to form metal nanoparticles both in porous media [23] and on flat surfaces [24]. In this study, we propose a simple technique for applying a layer of plasmonic gold nanoparticles to the surface of a porous TiO\({}_{2}\) film in order to increase its photoelectrochemical characteristics. Moreover, with the help of such photo-deposition it is possible to scale the process over large surface areas while maintaining the particle size distribution [24]. This will allow the formation of large area photoelectrodes with reproducible properties, which can become the basis for the formation of commercial artificial photosynthesis modules.