In Tandem Control of La-Doping and CuO-Heterojunction on SrTiO Perovskite by Double-Nozzle Flame Spray Pyrolysis: Selective H vs. CH Photocatalytic Production from HO/CHOH.

ABO perovskites offer versatile photoactive nano-templates that can be optimized towards specific technologies, either by means of doping or via heterojunction engineering. SrTiO is a well-studied perovskite photocatalyst, with a highly reducing conduction-band edge. Herein we present a Double-Nozzle Flame Spray Pyrolysis (DN-FSP) technology for the synthesis of high crystallinity SrTiO nanoparticles with controlled La-doping in tandem with SrTiO/CuO-heterojunction formation. So-produced La:SrTiO/CuO nanocatalysts were optimized for photocatalysis of HO/CHOH mixtures by varying the La-doping level in the range from 0.25 to 0.9%. We find that, in absence of CuO, the 0.9La:SrTiO material achieved maximal efficient photocatalytic H production, i.e., 12 mmol g h. Introduction of CuO on La:SrTiO enhanced selective production of methane CH. The optimized 0.25La:SrTiO/0.5%CuO catalyst achieved photocatalytic CH production of 1.5 mmol g h. Based on XRD, XRF, XPS, BET, and UV-Vis/DRS data, we discuss the photophysical basis of these trends and attribute them to the effect of La atoms in the SrTiO lattice regarding the H-production, plus the effect of interfacial CuO on the promotion of CH production. Technology-wise this work is among the first to exemplify the potential of DN-FSP for scalable production of complex nanomaterials such as La:SrTiO/CuO with a diligent control of doping and heterojunction in a single-step synthesis.