Hot electron flux at the solid-liquid interfaces probed with Pt/Si catalytic nanodiodes

Abstract

An in-depth understanding of chemical reactions occurring at solid-liquid interfaces is crucial for a large number of technological processes. These include heterogeneous catalysis, electrochemistry, corrosion, environmental science, development of energy sources, and others. At the same time, our knowledge about the processes which take place on the solid surfaces in a liquid medium remains incomplete. The main reason for this is that most of the conventional surface science methods are based on the use of various particles (electrons, ions, or atoms) to probe the surface. These methods work well under ultrahigh vacuum conditions. However, the use of them for the study of solid-liquid interfaces is limited due to the issues associated with the mean free path of the particles. Therefore, new experimental methods free from the above problems are needed. Hydrogen peroxide ($H_2O_2$) is used for an effective oxidizing agent which is common in industry. On the surface of metal catalysts, $H_2O_2$ is converted into oxygen and water. In order to understand this process at the elementary level is greatly important in many industrial applications, such as, the direct synthesis of $H_2O_2$ from $H_2$ and $O_2$. Using a chemicurrent approach, we not only studied chemical reactions at solid-liquid interface but also rate of $H_2O_2$ decomposition and the corresponding chemicurrent are sensitive to concentration and pH of the reactive solution. For that matter, $H_2O_2$ decomposition catalyzed on Pt/n-Si catalysts is used. which is based on detection of hot electrons created as a result of dissociative adsorption of $H_2O_2$ molecules on platinum. This phenomenon is explained by variations of the potential barrier for an electron transfer at the Pt/solution interface caused by adsorption of $H^+$ and $OH^-$ species from the solution on the catalytic surface.