Photoelectrochemical CO 2 Reduction to CO Enabled by a Molecular Catalyst Attached to High-Surface-Area Porous Silicon

• Published in: Journal of the American Chemical Society 2024-03, Vol.146 (12), p.7998-8004
• Main Authors: Jia, Xiaofan, Stewart-Jones, Eleanor, Alvarez-Hernandez, Jose L, Bein, Gabriella P, Dempsey, Jillian L, Donley, Carrie L, Hazari, Nilay, Houck, Madison N, Li, Min, Mayer, James M, Nedzbala, Hannah S, Powers, Rebecca E
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c10837

A high-surface-area -type porous Si photocathode containing a covalently immobilized molecular Re catalyst is highly selective for the photoelectrochemical conversion of CO to CO. It gives Faradaic efficiencies of up to 90% for CO at potentials of -1.7 V (versus ferrocenium/ferrocene) under 1 sun illumination in an acetonitrile solution containing phenol. The photovoltage is approximately 300 mV based on comparisons with similar -type porous Si cathodes in the dark. Using an estimate of the equilibrium potential for CO reduction to CO under optimized reaction conditions, photoelectrolysis was performed at a small overpotential, and the onset of electrocatalysis in cyclic voltammograms occurred at a modest underpotential. The porous Si photoelectrode is more stable and selective for CO production than the photoelectrode generated by attaching the same Re catalyst to a planar Si wafer. Further, facile characterization of the porous Si-based photoelectrodes using transmission mode FTIR spectroscopy leads to highly reproducible catalytic performance.