Rational design of Au@Pd core–shell cocatalyst on titanium dioxide enabling selective photocatalytic formation of deuterated alkane from lauric acid and heavy water

Abstract

Photocatalytic decarboxylative deuteration using heavy water is a promising approach for the synthesis of deuterated alkane, where high reaction selectivity is essential. In this study, Au@Pd-loaded TiO₂ photocatalysts are prepared via a simultaneous photodeposition (SPD) method under various conditions, and the effects of the preparation conditions on cocatalyst structure, as well as the resulting photocatalytic activity and selectivity toward deuterated undecane formation from lauric acid and heavy water, are systematically investigated. In the SPD process, efficient reduction of the metal precursors with a higher density of the photoexcited electrons, which can be provided by high light intensity or efficient sacrificial reagents such as methanol, leads to the formation of Au@Pd core–shell nanoparticles covered with a Pd-rich shell surface, resulting in a high yield and selectivity for deuterated undecane. The Au@Pd core–shell part has concentration gradient of Au and Pd to accelerate smooth migration from the Au core to the Pd-rich surface after receiving the photoexcited electron from TiO₂ surface, enhancing the photocatalytic activity due to high electron density at the Pd surface, and the Pd-rich surface consists of almost pure Pd, promoting the deuterium ion reduction to deuterium radical and successive reaction between the generated deuterium radical and undecyl radical generated by hole oxidation on the TiO₂ surface. This acceleration contributes to the high selectivity for the deuteration. These results demonstrate that rational control of photodeposition parameters to fabricate the well-designed functional cocatalyst is a promising strategy to obtain high photocatalytic activity and reaction selectivity in the photocatalytic synthesis of deuterated alkane.