A Molecular Silane-Derivatized Ru(II) Catalyst for Photoelectrochemical Water Oxidation

• Published in: Journal of the American Chemical Society 2018-11, Vol.140 (44), p.15062-15069
• Main Authors: Wu, Lei, Eberhart, Michael, Nayak, Animesh, Brennaman, M. Kyle, Shan, Bing, Meyer, Thomas J
• Format: Article
• Language: English
• Subjects: catalysis (heterogeneous); catalysis (homogeneous); charge transport; defects; electrocatalysis; ENERGY STORAGE; materials and chemistry by design; mesostructured materials; photosynthesis (natural and artificial); solar (fuels); synthesis (novel materials); synthesis (self-assembly)
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b10132

Photoanodes in dye-sensitized photoelectrosynthesis cells integrate molecular chromophore/catalyst assemblies on mesoporous n-type metal oxide electrodes for light-driven water oxidation. One limitation for sustainable photoanodes is the stability of chromophore/catalyst assembly on electrode surfaces for long periods. Progress has been made in stabilizing chromophores based on atomic layer deposition, polymer dip coating, C–C cross-coupling by electropolymerization, and silane surface binding, but little progress has been made on catalyst stabilization. We report here the silane-derivatized catalyst, Ru­(bda)­(L)2 (bda = 2,2′-bipyridine-6,6′-dicarboxylate, L = 4-(6-(triethoxysilyl)­hexyl)­pyridine), catalyst 1, which is stabilized on metal oxide electrode surfaces over an extended pH range. A surface stabilization study shows that it maintains its reactivity on the electrode surface toward electrochemical oxidation over a wide range of conditions. Its electrochemical stability on electrode surfaces has been systematically evaluated, and its role as a catalyst for water oxidation has been explored. On surfaces of mesoporous nanostructured core/shell SnO2/TiO2, with a TiO2 stabilized inner layer of the Ru­(II) polypyridyl chromophore, [Ru­(4,4′-(PO3H2)2bpy)­(bpy)2]2+ (RuP 2+ ; bpy = 2,2′-bipyridine), highly efficient photoelectrochemical water oxidation catalysis occurs to produce O2 with a maximum efficiency of ∼1.25 mA/cm2. Long-term loss of catalytic activity occurs with time owing to catalyst loss from the electrode surface by axial ligand dissociation in the high oxidation states of the catalyst.