Room-temperature conversion of Cu2−xSe to CuAgSe nanoparticles to enhance the photocatalytic performance of their composites with TiO2

Rational design and precise engineering are needed to optimize the structural and chemical parameters of functional materials. In this work, we demonstrate how pre-formed binary metal selenide can be an excellent synthetic choice for the synthesis of ternary coinage metal selenide nanoparticles (NPs) with controlled composition. The mild conditions required to obtain these ternary coinage metal selenide NPs offered an easy synthesis of n%CuAgSe-TiO2 (n = 0.01, 0.1, 0.3 and 1.0 mol%) nanocomposites for photocatalytic application without compromising with the structural and morphological characteristics of TiO2 and without having any organics around NPs. The use of the ternary metal selenide nanocomposites CuAgSe-TiO2 results in a clear improvement in its photocatalytic activity for the photodegradation of formic acid as compared to the well-known benchmark for photocatalysis TiO2 (P25) and its binary metal selenide nanocomposites Cu2-xSe-TiO2. The DFT calculations establish a semi-metallic behavior for CuAgSe NPs and show that CuAgSe-TiO2 forms a semimetallic-semiconductor heterojunction allowing a better charge separation to enhance its photocatalytic activity.