Defect-Driven Dynamics in Gas-Phase Photocatalytic CO <sub>2</sub> Conversion to Solar Fuels Using Ti <sup> 3 <b>+</b> </sup> /Ti <sup> 4 <b>+</b> </sup> Containing TiO <sub>2</sub> and Nonstoichiometric Ag <sub>2</sub> S Nanowires
Niket S. Powar, Soonho Kwon, Chaitanya B. Hiragond, Junho Lee, Eunhee Gong, Hong Soo Kim, Dongyun Kim, William A. Goddard, Su‐Il In
Abstract
High Resolution Image Download MS PowerPoint Slide We studied CO 2 photoreduction on nonstoichiometric surface photocatalysts using a comprehensive approach combining materials design, advanced spectroscopy, and Quantum Mechanics (QM) calculations. We developed a direct Z-scheme heterostructure, A-TiO 2 /Ag 2 S NWs, composed of amorphous TiO 2 and nonstoichiometric Ag 2 S nanowires. This structure promotes defect-rich characteristics and a strong internal electric field (IEF), enhancing charge separation and minimizing electron–hole recombination. Employing in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and QM-simulated IR spectra revealed the CO 2 -to-CH 4 conversion mechanism which involves H 2 COH* intermediate. Ti 3+ /Ti 4+ and Ag + defect environments were precisely characterized through X-ray photoelectron spectroscopy (XPS) and in situ extended X-ray absorption fine structure (EXAFS). Under concentrated solar illumination, this heterostructure achieved a CH 4 production rate of 30.31 μmol/g, a 5-fold enhancement over conventional 1-sun conditions. These findings provide valuable insights into solar-driven fuel synthesis through targeted defect engineering and strategic heterostructure design.