Binding Mode of Malonic Acid on the IrO2 Surface

Abstract

Malonic acid possessing two carboxylic acid anchoring groups is employed as the anchoring group to attach molecular dyes onto IrO₂ nanoparticles to oxidize water in a dye-sensitized water splitting system. Yet, the detailed binding modes and nanoscopic structures of malonic acid on the IrO₂ substrate are not thoroughly investigated due to the sophisticated structure. Previous researches assume that malonic acid interacts with the IrO₂ nanoparticles via two carbonyl groups. In this study, we present first principles calculations on the interfacial structures of malonic acid/IrO₂ and state that this assumption is incorrect. Instead, we propose that multiple stable adsorption modes are available at the molecule/IrO₂ interface. The associated electronic properties corresponding to different binding modes are discussed.