Enhancing optical phonon energies and persistent yield production of CO via substitutional doping in indium oxide

We report on photo-related effects from doping for the reverse water gas shift reaction: enhanced photo-thermalization, and persistent CO yield post illumination generating a ‘memory’ effect. Bismuth substitution doping of Indium in Bi_z- In₂O_3-x(OH)_y material systems results in significantly increased CO rate with increasing photo-intensities. Urbach analysis reveals that optical-phonon energies in doped systems increase compared to undoped systems by a factor of 1.18–1.41 in CO₂+H₂ atmosphere, suggesting enhanced photo-thermalization at high photo-intensities. Persistent CO yield post photo-illumination for high-doped In₂O_3-x(OH)_y has a persistent period of 60 min in flow reactor with decay constant of 24.3 h in batch reactor, enhancing yield by 78% and 17%; low-doped and undoped systems present shorter prolonged production times with 30−40 min in flow reactor with longer decay constant of 31.0–31.5 hours in batch reactor. Linked to slow photocurrent decay trends which extends for 1−2 hours in undoped system, and more than 2 h for high doped system.