Electrocatalytic CO2 Reduction with a Ruthenium Catalyst in Solution and on Nanocrystalline TiO2

• Published in: ChemSusChem Vol. 12; no. 11; pp. 2402 - 2408
• Main Authors: Li, Ting‐Ting, Shan, Bing, Xu, Wei, Meyer, Thomas J.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 07.06.2019; ChemPubSoc Europe
• Subjects: Carbon dioxide; carbon dioxide reduction; Carbon monoxide; Catalysis; Catalysts; Chemical reduction; Chemistry; Electrocatalysis; Electrodes; heterogenization; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; low overpotential; Molecular structure; Nanocrystals; Phenyl phosphonate; Phosphonates; Photoelectrons; Reflectance; Ruthenium; ruthenium complex; Science & Technology - Other Topics; Titanium dioxide; Heterogenization; low overpotential; CO2 reduction; electrocatalysis; Ruthenium complex
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201900730

A RuII complex [Ru(PO3Et2‐ph‐tpy)(6‐mbpy)(NCCH3)]2+ [PO3Et2‐ph‐tpy=diethyl(4‐[(2,2′:6′,2′′‐terpyridin)‐4′‐yl]phenyl)phosphonate; 6‐mbpy=6‐methyl‐2,2′‐bipyridine] is explored as a molecular catalyst for electrocatalytic CO2 reduction in both a homogeneous solution and, as a phosphonated derivative, on nanocrystalline‐TiO2 surfaces. In CH3CN, the complex acts as a selective electrocatalyst for reduction of CO2 to CO at a low overpotential of 340 mV but with a limited turnover number (TON). An enhancement in reactivity was observed by immobilizing the phosphonated derivative of the catalyst on a nanocrystalline‐TiO2 electrode surface, with the catalyst surface protected by a thin overlayer of NiO. The surface‐functionalized electrode was characterized by X‐ray photoelectron and diffuse reflectance spectroscopies (XPS and DRS). Electrocatalytic reduction of CO2 to CO occurred at −1.65 V versus Fc+/0 with a TON of 237 per catalyst site during 4 h of electrocatalysis. Post‐catalysis XPS measurements reveal that the molecular structure of the catalyst is retained on TiO2 after the long‐term electrocatalysis. A wholesome catalyst: Electrocatalytic CO2 reduction to CO was demonstrated for a ruthenium(II) polypyridyl catalyst on a nano‐crystalline TiO2 electrode with a low catalytic overpotential and a turnover number of 237. The synthesized Ru complex is retained on the electrode even after 4 h of bulk electrocatalysis.