Nonadiabatic electron excitation in exothermic chemical reactions leads to the flow of energetic electrons with an energy of 1–3 eV, which are called “hot electrons”. Direct detection of hot electron flow and the observation of its role in catalytic reactions are important for understanding metal–oxide heterogeneous catalysis. Recently, some studies have reported different catalytic reaction kinetics at solid/gas and solid/liquid interfaces; however, there has been no quantitative comparison of hot electron generation at solid/gas and solid/liquid interfaces. Herein, using a Pt/n-type Si Schottky nanodiode, we show the production of hot electron flow generated by the H2O2 decomposition reaction on a Pt thin film for both the gas and liquid phases, and detect a steady-state hot electron current (chemicurrent) that is generated by exothermic chemical reactions on the Pt catalyst surface. Exponential decay of the chemicurrent dependent on the metal catalyst thickness can be evidence of the ballistic transport of hot electrons, excited on the Pt film surface during the chemical reaction, through the catalyst film without collision. In addition, we monitored the change in pressure to determine the rate of oxygen formation by H2O2 decomposition for both the gas and liquid phases. Interestingly, the oxygen evolution rate in the liquid phase was about 10 times lower than that in the gas phase, however, the chemicurrent was about 10 times higher at the solid/liquid interface. Furthermore, we estimated the chemicurrent yield, which is the number of hot electrons detected per chemical reaction on the nanodiode surface (i.e., the efficiency of hot electron generation on the catalyst surface), and the chemicurrent yield was 2 orders of magnitude higher at the solid/liquid interface than that at the solid/gas interface for all reaction temperatures. We discuss the possible mechanism for hot electron generation on the catalyst surface between the solid/gas and solid/liquid interfaces, which was further confirmed via theoretical calculations based on density functional theory.

Chemically induced hot electrons at solid/gas and solid/liquid interfaces during hydrogen peroxide decomposition

2019 Fall National Meeting

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