In Tandem Control of La-Doping and CuO-Heterojunction on SrTiO 3 Perovskite by Double-Nozzle Flame Spray Pyrolysis: Selective H 2 vs. CH 4 Photocatalytic Production from H 2 O/CH 3 OH.

ABO 3 perovskites offer versatile photoactive nano-templates that can be optimized towards specific technologies, either by means of doping or via heterojunction engineering. SrTiO 3 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 3 nanoparticles with controlled La-doping in tandem with SrTiO 3 /CuO-heterojunction formation. So-produced La:SrTiO 3 /CuO nanocatalysts were optimized for photocatalysis of H 2 O/CH 3 OH 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 3 material achieved maximal efficient photocatalytic H 2 production, i.e., 12 mmol g -1 h -1 . Introduction of CuO on La:SrTiO 3 enhanced selective production of methane CH 4 . The optimized 0.25La:SrTiO 3 /0.5%CuO catalyst achieved photocatalytic CH 4 production of 1.5 mmol g -1 h -1 . 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 3 lattice regarding the H 2 -production, plus the effect of interfacial CuO on the promotion of CH 4 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 3 /CuO with a diligent control of doping and heterojunction in a single-step synthesis.