Photothermal flash light doping of strontium titanate photocatalyst nanoparticles

Rhodium and lanthanum co-doped strontium titanate (Rh,La:SrTiO$_3$) is a promising material for green hydrogen (H$_2$) production via heterogeneous photocatalytic (PC) water splitting. State-of-the-art Rh,La:SrTiO$_3$ nanoparticle photocatalysts mitigate charge recombination using an undoped core/doped shell structure. However, the typically-employed synthesis methods use high temperatures >1000 °C in a slow dopant diffusion process, which induces inhomogeneities, causes nanoparticle sintering, and limits material performance. In this work, we demonstrate a rapid flash light annealing (FLA) technique that affords suitable nanoparticle doping in only 7.5 seconds. FLA samples show a PC performance three times greater than conventional thermal doping, which we attribute to mitigated particle sintering and dopants incorporated closer to the surface. Moreover, the H$_2$ evolution rate under full spectrum simulated solar illumination increased by 50% compared to the undoped precursor nanoparticles. Finally, varying the flash parameters shows the tunability of the FLA process. The developed method paves the way for extending rapid doping by FLA to other powdered materials without the need for ion implantation.