Modulation of Excitonic Confinement of TiO2 in Molten Salts for Overall CO2 Photoreduction

Excitonic confinement greatly determines the charge carrier transport of photocatalysts. A molten salt modulation of excitonic confinement is herein demonstrated as formation of ultrafine carbon-doped anatase TiO2 with grafted graphitic carbon nitride, which is rationalized as an excellent catalyst for overall CO2 photoreduction. Compared with bulk TiO2, the carbon-doped TiO2 (M-TiO2) possesses a weaker excitonic confinement to decrease exciton binding energy from 99 to 58 meV, consequently enhancing free-charge-carrier generation and transportation. Effective Z-scheme electron transfer from M-TiO2 to C3N4 is built, enhancing the CO2 conversion via the synchronous optimization of redox ability, CO2 activation, and *COOH generation. This work highlights the unique chemistry of excitonic dissociation on facilitating separation of electron and hole, and also extends the scope of molten salt-mediated modulation of photocatalysis materials.

Automated summary

Excitonic confinement of carbon-doped TiO2 is modulated by molten salt, leading to the formation of ultrafine carbon-doped anatase TiO2 with graphitic carbon nitride. This composite acts as an excellent catalyst for overall CO2 photoreduction, with enhanced free-charge-carrier generation and transportation. Effective Z-scheme electron transfer and optimization of redox ability, CO2 activation, and *COOH generation contribute to improved CO2 conversion.