Mechanistic insights into photocatalysis and over two days of stable H generation in electrocatalysis by a molecular cobalt catalyst immobilized on TiO

• Published in: Catalysis science & technology 2020-04, Vol.1 (8), p.2549-256
• Main Authors: Weder, Nicola, Probst, Benjamin, Sévery, Laurent, Fernández-Terán, Ricardo J, Beckord, Jan, Blacque, Olivier, Tilley, S. David, Hamm, Peter, Osterwalder, Jürg, Alberto, Roger
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d0cy00330a

To employ molecular water reduction catalysts (WRC) in a heterogeneous setup, a stable, macrocyclic Co III -polypyridyl WRC containing two phosphonic acid groups was anchored on TiO 2 to investigate photo- and electrocatalytic proton reduction. Photocatalytic investigations included kinetic studies of the electron transfer from the reduced photosensitizer to the WRC as well as H 2 -evolution measurements. Linear sweep voltammetry (LSV) performed on the immobilized WRC on a TiO 2 -coated FTO-glass electrode showed an onset potential of −0.6 V vs. SHE at pH = 5 for proton reduction, while operando UV/VIS confirmed the reduced Co I -species as the key catalytic intermediate. Finally, chronoamperometric investigations combined with XPS studies and ICP-MS studies of electrode and electrolyte revealed stable binding of the WRC on the electrode under catalytic conditions and constant H 2 -formation over the period of two days. Molecular and heterogeneous water reduction combined: Over 2 days of electrocatalysis of a cobalt polypyridyl catalyst immobilized on TiO 2 .