Abstract
Tungsten trioxide (WO3) and titanium oxide are known as photocatalysts that oxidize and decompose organic compounds. Hydroxyl radicals (•OH) generated during water oxidation not only decompose organic substances but also cause other selective oxidation reactions. However, the behavior of •OH production under different reaction conditions is not completely understood. The purpose of this study is to quantitatively analyze the •OH generated during the photoanodic reaction on photocatalyst electrodes. Herein, we developed a novel electrolyte flow-type electron spin resonance (ESR) method using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trapping agent to analyze the Faraday efficiency of •OH production in near real-time response. The WO3 photoanode was prepared by a dip coating method using Ti felt as the conductive substrate. When the WO3 electrode was irradiated with ultraviolet light at 1.2 V vs. RHE, four ESR signals were observed, and the formation of •OH (•DMPO-OH) was confirmed from the g value and hyperfine coupling constant. The amount of •OH produced was quantified every minute by comparing the double-integrated intensity of this signal with that of a standard sample. The results showed that the Faraday efficiency of the total amount of •OH in WO3 was low, less than 1%, and most of the photocurrent was used for oxygen evolution reaction. In the presentation, we will also report on the dependence of •OH formation on applied potential and incident light intensity. Figure 1
Published Version
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