Rock-Salt Entropy-Stabilized Oxide Nanoparticles for Photocatalytic Hydrogen Production

The emergence of entropy-stabilized oxides has transformed the paradigm of functional materials design, in particular, for catalytic applications. However, the high-temperature treatments usually used for their synthesis lead to the formation of large particles with a small specific active surface and low photocatalytic efficiency. In this work, we use a top-down approach to downsize rock-salt entropy-stabilized oxide (Mg 0.2 Ni 0.2 Zn 0.2 Co 0.2 Li 0.1 Ga 0.1 )O particles to the nanometric scale using a mechanical ball-milling process. This two-step process is easily scalable and enables the synthesis of entropy-stabilized nanoparticles with well-controlled and easily tunable chemical composition. The particle sizes obtained under dry ball milling were in the range of 4–7 nm, with an increase in the specific surface area up to 6.6 m 2 g –1 . Besides, we observed a partial reduction of the cations during the ball-milling process, affecting the optical bandgap of the nanomaterials compared to the bulk material. Under optimal conditions, photocatalytic H 2 generation reached 111 μmol.g –1 after 4 h of illumination in the presence of triethanolamine.