Aqueous CO2 Reduction on Si Photocathodes Functionalized by Cobalt Molecular Catalysts/Carbon Nanotubes

• Published in: Angewandte Chemie International Edition Vol. 61; no. 24; pp. e202201086 - n/a
• Main Authors: Wen, Zhibing, Xu, Suxian, Zhu, Yong, Liu, Guoquan, Gao, Hua, Sun, Licheng, Li, Fei
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 13.06.2022
• Edition: International ed. in English
• Subjects: Aqueous solutions; Carbon dioxide; Carbon Dioxide Reduction; catalyst; Catalyst selectivity; Catalysts; CO 2 reduction; Coated electrodes; Cobalt; Cobalt Complexes; Cobalt complexes (III); Cobalt compounds; Field emission cathodes; Fuel production; Functionalized; Hybrid Materials; Hybrids material; Molecular catalysts; Multi wall carbon nanotubes; Multiwalled carbon nanotubes (MWCN); Nanotechnology; Nanotubes; Photocathode; Photocathodes; Photoelectric effect; Photoelectrochemicals; Reduction; Selectivity; Silicon; Titanium dioxide
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202201086

Photoelectrochemical reduction of CO2 is a promising approach for renewable fuel production. We herein report a novel strategy for preparation of hybrid photocathodes by immobilizing molecular cobalt catalysts on TiO2‐protected n+‐p Si electrodes (Si|TiO2) coated with multiwalled carbon nanotubes (CNTs) by π–π stacking. Upon loading a composite of CoII(BrqPy) (BrqPy=4′,4′′‐bis(4‐bromophenyl)‐2,2′ : 6′,2′′ : 6′′,2′′′‐quaterpyridine) catalyst and CNT on Si|TiO2, a stable 1‐Sun photocurrent density of −1.5 mA cm−2 was sustained over 2 h in a neutral aqueous solution with unity Faradaic efficiency and selectivity for CO production at a bias of zero overpotential (−0.11 V vs. RHE), associated with a turnover frequency (TOFCO) of 2.7 s−1. Extending the photoelectrocatalysis to 10 h, a remarkable turnover number (TONCO) of 57000 was obtained. The high performance shown here is substantially improved from the previously reported photocathodes relying on covalently anchored catalysts. A hybrid photocathode prepared by attaching a molecular cobalt catalyst on a n+‐p Si film coated with multiwalled carbon nanotubes (CNTs) exhibits 100 % selectivity and 100 % Faradaic efficiency towards CO2‐to‐CO conversion in aqueous media under simulated sunlight irradiation. The high performance benefits from CNTs as both a support platform for highly dispersed molecular active sites and an efficient mediator for charge transfer.